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ksh(1) [ultrix man page]

ksh(1)							      General Commands Manual							    ksh(1)

Name
       ksh, rksh - KornShell, a standard/restricted command and programming language

Syntax
       ksh [ +-aefhikmnoprstuvx ] [ +-o option ] ...  [ -c string ] [ arg ... ]
       rksh [ +-aefhikmnoprstuvx ] [ +-o option ] ...  [ -c string ] [ arg ... ]

Description
       The shell is a command and programming language that executes commands read from a terminal or a file.  The rksh shell is a restricted ver-
       sion of the command interpreter ksh; it is used to set up login names and execution environments whose  capabilities  are  more	controlled
       than those of the standard shell.  See Invocation for the meaning of arguments to the shell.

   Definitions
       A metacharacter is one of the following characters:

	      ;   &   (   )   |   <   >   new-line   space   tab

       A blank is a tab or a space.  An identifier is a sequence of letters, digits, or underscores starting with a letter or underscore.  Identi-
       fiers are used as names for functions and `named parameters'.  A word is a sequence of characters  separated  by  one  or  more	non-quoted
       metacharacters.

       A command is a sequence of characters in the syntax of the shell language.  The shell reads each command and carries out the desired action
       either directly or by invoking separate utilities.  A special command is a command that is carried out by the shell without creating a sep-
       arate process.  Except for documented side effects, most special commands can be implemented as separate utilities.

   Commands
       A  simple-command is a sequence of blank separated words which may be preceded by a parameter assignment list.  See Environment below.  The
       first word specifies the name of the command to be executed.  Except as specified below, the remaining words are passed as arguments to the
       invoked command.  The command name is passed as argument 0 (see The value of a simple-command is its exit status if it terminates normally,
       or (octal) 200+status if it terminates abnormally (see for a list of status values).

       A pipeline is a sequence of one or more commands separated by |.  The standard output of each command but the last is connected by a to the
       standard  input	of  the  next command.	Each command is run as a separate process; the shell waits for the last command to terminate.  The
       exit status of a pipeline is the exit status of the last command.

       A list is a sequence of one or more pipelines separated by ;, &, &&, or ||, and optionally terminated by ;, &, or |&.  Of these	five  sym-
       bols,  ;,  &,  and  |&  have equal precedence, which is lower than that of && and ||.  The symbols && and || also have equal precedence.  A
       semicolon (;) causes sequential execution of the preceding pipeline; an ampersand (&) causes asynchronous execution of the preceding  pipe-
       line  (that is, the shell does not wait for that pipeline to finish).  The symbol |& causes asynchronous execution of the preceding command
       or pipeline with a two-way pipe established to the parent shell.  The standard input and output of the spawned command can  be  written	to
       and  read  from	by the parent Shell using the -p option of the special commands read and print described later.  The symbol && (||) causes
       the list following it to be executed only if the preceding pipeline returns a zero (non-zero) value.  An arbitrary number of new-lines  may
       appear in a list, instead of a semicolon, to delimit a command.

       A command is either a simple-command or one of the following.  Unless otherwise stated, the value returned by a command is that of the last
       simple-command executed in the command.

       for identifier [ in word ... ] ;do list ;done
	      Each time a for command is executed, identifier is set to the next word taken from the in word list.  If in word	...   is  omitted,
	      then  the  for command executes the do list once for each positional parameter that is set (see Parameter Substitution ).  Execution
	      ends when there are no more words in the list.

       select identifier [ in word ... ] ;do list ;done
	      A select command prints on standard error (file descriptor 2), the set of words, each preceded by a number.   If	in  word  ...	is
	      omitted,	then  the positional parameters are used instead (see Parameter Substitution below).  The PS3 prompt is printed and a line
	      is read from the standard input.	If this line consists of the number of one of the listed words, then the value	of  the  parameter
	      identifier  is  set to the word corresponding to this number.  If this line is empty the selection list is printed again.  Otherwise
	      the value of the parameter identifier is set to null.  The contents of the line read from standard input is saved in  the  parameter
	      REPLY.  The list is executed for each selection until a break or end-of-file is encountered.

       case word in [ [(]pattern [ | pattern ] ... ) list ;; ] ... esac
	      A  case command executes the list associated with the first pattern that matches word.  The form of the patterns is the same as that
	      used for file-name generation (see File Name Generation below).

       if list ;then list [ elif list ;then list ] ... [ ;else list ] ;fi
	      The list following if is executed and, if it returns a zero exit status, the list following the first then is executed.	Otherwise,
	      the list following elif is executed and, if its value is zero, the list following the next then is executed.  Failing that, the else
	      list is executed.  If no else list or then list is executed, then the if command returns a zero exit status.

       while list ;do list ;done
       until list ;do list ;done
	      A while command repeatedly executes the while list and, if the exit status of the last command in the list is zero, executes the	do
	      list; otherwise the loop terminates.  If no commands in the do list are executed, then the while command returns a zero exit status;
	      until may be used in place of while to negate the loop termination test.

       (list) Execute list in a separate environment.  Note, that if two adjacent open parentheses  are  needed  for  nesting,	a  space  must	be
	      inserted to avoid arithmetic evaluation as described below.

       { list;}
	      The list is simply executed.  Note that unlike the metacharacters ( and ),
	      { and } are `reserved words' and must at the beginning of a line or after a ; in order to be recognized.

       [[expression]]
	      Evaluates  expression  and  returns  a  zero  exit status when expression is true.  See Conditional Expressions for a description of
	      expression.

       function identifier { list ;}
       identifier () { list ;}
	      Define a function which is referenced by identifier.  The body of the function is the list of commands between { and }.  (See  Func-
	      tions below).

       time pipeline
	      The pipeline is executed and the elapsed time as well as the user and system time are printed on standard error.

       The following reserved words are only recognized as the first word of a command and when not quoted:

       if then else elif fi case esac for while until do done { } function select time [[ ]]

   Comments
       A word beginning with # causes that word and all the following characters up to a new-line to be ignored.

   Aliasing
       The  first  word of each command is replaced by the text of an alias if an alias for this word has been defined.  The first character of an
       alias name can be any non-special printable character, but the rest of the characters must be the same as  for  a  valid  identifier.   The
       replacement  string  can  contain  any valid Shell script including the metacharacters listed above.  The first word of each command in the
       replaced text, other than any that are in the process of being replaced, will be tested for aliases.  If the last character  of	the  alias
       value  is  a  blank then the word following the alias will also be checked for alias substitution.  Aliases can be used to redefine special
       builtin commands but cannot be used to redefine the reserved words listed above.  Aliases can be created, listed,  and  exported  with  the
       command	and can be removed with the command.  Exported aliases remain in effect for scripts invoked by name, but must be reinitialized for
       separate invocations of the Shell (See Invocation below).

       Aliasing is performed when scripts are read, not while they are executed.  Therefore, for an alias to take effect the alias definition com-
       mand has to be executed before the command which references the alias is read.

       Aliases	are  frequently  used as a short hand for full path names.  An option to the aliasing facility allows the value of the alias to be
       automatically set to the full pathname of the corresponding command.  These aliases are called tracked aliases.	The  value  of	a  tracked
       alias  is  defined the first time the corresponding command is looked up and becomes undefined each time the PATH variable is reset.  These
       aliases remain tracked so that the next subsequent reference will redefine the value.  Several tracked aliases are compiled into the shell.
       The -h option of the command makes each referenced command name into a tracked alias.

       The following `exported aliases' are compiled into the shell but can be unset or redefined:
	    autoload='typeset -fu'
	    false='let 0'
	    functions='typeset -f'
	    hash='alias -t'
	    history='fc -l'
	    integer='typeset -i'
	    nohup='nohup '
	    r='fc -e -'
	    true=':'
	    type='whence -v'

   Tilde Substitution
       After alias substitution is performed, each word is checked to see if it begins with an unquoted ~.  If it does, then the word up to a / is
       checked to see if it matches a user name in the file.  If a match is found, the ~ and the matched login	name  is  replaced  by	the  login
       directory  of the matched user.	This is called a `tilde substitution'.	If no match is found, the original text is left unchanged.  A ~ by
       itself, or in front of a /, is replaced by the value of the HOME parameter.  A ~ followed by a + or -  is  replaced  by	$PWD  and  $OLDPWD
       respectively.

       In addition, tilde substitution is attempted when the value of a `variable assignment parameter' begins with a ~.

   Command Substitution
       The standard output from a command enclosed in parentheses preceded by a dollar sign ( $() ) or a pair of grave accents may be used as part
       or all of a word; trailing new-lines are removed.  In the second (archaic) form, the string between the quotes  is  processed  for  special
       quoting	characters  before the command is executed. (See Quoting).  The command substitution $(cat file) can be replaced by the equivalent
       but faster $(<file).  Command substitution of most special commands that do not perform input/output redirection are  carried  out  without
       creating a separate process.

       An  arithmetic  expression  enclosed  in  double parenthesis preceded by a dollar sign ( $(()) ) is replaced by the value of the arithmetic
       expression within the double parenthesis.

   Process Substitution.
       This feature is only available on versions of the operating system that support the directory for naming open files.  Each command argument
       of  the	form <(list) or >(list) will run process list asynchronously connected to some file in The name of this file will become the argu-
       ment to the command.  If the form with > is selected then writing on this file will provide input for list.  If < is used,  then  the  file
       passed as an argument will contain the output of the list process.  For example,

	      paste <(cut -f1 file1) <(cut -f3 file2) | tee >(process1) >(process2)

       cuts  fields  1	and 3 from the files file1 and file2 respectively, pastes the results together, and sends it to the processes process1 and
       process2, as well as putting it onto the standard output.  Note that the file, which is passed as an argument to the command, is  a  system
       so programs that expect to on the file will not work.

   Parameter Substitution
       A  parameter  is  an  identifier,  one  or more digits, or any of the characters *, @, #, ?, -, $, and !.  A `named parameter' (a parameter
       denoted by an identifier) has a value and zero or more attributes.  Named parameters can be assigned values and	attributes  by	using  the
       special	command.  The attributes supported by the Shell are described later with the special command.  Exported parameters pass values and
       attributes to the environment.

       The shell supports a one-dimensional array facility.  An element of an array parameter is  referenced  by  a  subscript.   A  subscript	is
       denoted	by a [, followed by an `arithmetic expression' (see Arithmetic Evaluation) followed by a ].  To assign values to an array, use set
       -A name	value ... .  The value of all subscripts must be in the range of 0 through 1023.  Arrays need not be declared.	Any reference to a
       named  parameter  with  a  valid subscript is legal and an array will be created if necessary.  Referencing an array without a subscript is
       equivalent to referencing the element zero.

       The value of a named parameter may also be assigned by writing:

	      name=value [ name=value ] ...

       If the integer attribute, -i, is set for name the value is subject to arithmetic evaluation as described below.
       Positional parameters, parameters denoted by a number, may be assigned values with the special command.	Parameter $0 is set from  argument
       zero when the shell is invoked.
       The character $ is used to introduce substitutable parameters.
       ${parameter}
	      The  shell reads all the characters from ${ to the matching } as part of the same word even if it contains braces or metacharacters.
	      The value, if any, of the parameter is substituted.  The braces are required when parameter is  followed	by  a  letter,	digit,	or
	      underscore  that is not to be interpreted as part of its name or when a named parameter is subscripted.  If parameter is one or more
	      digits then it is a positional parameter.  A positional parameter of more than one digit must be enclosed in braces.   If  parameter
	      is  * or @, then all the positional parameters, starting with $1, are substituted (separated by a field separator character).  If an
	      array identifier with subscript * or @ is used, then the value for each of the elements is substituted (separated by a field separa-
	      tor character).
       ${#parameter}
	      If  parameter is * or @, the number of positional parameters is substituted.  Otherwise, the length of the value of the parameter is
	      substituted.
       ${#identifier[*]}
	      The number of elements in the array identifier is substituted.
       ${parameter:-word}
	      If parameter is set and is non-null then substitute its value; otherwise substitute word.
       ${parameter:=word}
	      If parameter is not set or is null then set it to word; the value of the parameter is then substituted.  Positional  parameters  may
	      not be assigned to in this way.
       ${parameter:?word}
	      If  parameter  is  set and is non-null then substitute its value; otherwise, print word and exit from the shell.	If word is omitted
	      then a standard message is printed.
       ${parameter:+word}
	      If parameter is set and is non-null then substitute word; otherwise substitute nothing.
       ${parameter#pattern}
       ${parameter##pattern}
	      If the Shell pattern matches the beginning of the value of parameter, then the value of this substitution is the value of the param-
	      eter  with the matched portion deleted; otherwise the value of this parameter is substituted.  In the first form the smallest match-
	      ing pattern is deleted and in the second form the largest matching pattern is deleted.

       ${parameter%pattern}
       ${parameter%%pattern}
	      If the Shell pattern matches the end of the value of parameter, then the value of this substitution is the value	of  the  parameter
	      with  the  matched  part	deleted;  otherwise substitute the value of parameter.	In the first form the smallest matching pattern is
	      deleted and in the second form the largest matching pattern is deleted.

       In the above, word is not evaluated unless it is to be used as the substituted string, so that, in the following example, is executed  only
       if d is not set or is null:

	      echo ${d:-$(pwd)}

       If the colon ( : ) is omitted from the above expressions, then the shell only checks whether parameter is set or not.

       The following parameters are automatically set by the shell:
	      # 	The number of positional parameters in decimal.
	      - 	Flags supplied to the shell on invocation or by the command.
	      ? 	The decimal value returned by the last executed command.
	      $ 	The process number of this shell.
	      _ 	Initially, the value _ is an absolute pathname of the shell or script being executed as passed in the environment.  Subse-
			quently it is assigned the last argument of the previous command.  This parameter is not set for commands which are  asyn-
			chronous.  file when checking for mail.
	      ! 	The process number of the last background command invoked.
	      ERRNO	The  value  of	errno  as set by the most recently failed system call.	This value is system dependent and is intended for
			debugging purposes.
	      LINENO	The line number of the current line within the script or function being executed.
	      OLDPWD	The previous working directory set by the command.
	      OPTARG	The value of the last option argument processed by the special command.
	      OPTIND	The index of the last option argument processed by the special command.
	      PPID	The process number of the parent of the shell.
	      PWD	The present working directory set by the command.
	      RANDOM	Each time this parameter is referenced, a random integer, uniformly distributed between 0 and 32767,  is  generated.   The
			sequence of random numbers can be initialized by assigning a numeric value to RANDOM.
	      REPLY	This parameter is set by the select statement and by the read special command when no arguments are supplied.
	      SECONDS	Each  time  this  parameter is referenced, the number of seconds since shell invocation is returned.  If this parameter is
			assigned a value, then the value returned upon reference will be the value that was assigned plus the  number  of  seconds
			since the assignment.

       The following parameters are used by the shell:
	      CDPATH The search path for the command.
	      COLUMNS
		     If  this  variable is set, the value is used to define the width of the edit window for the shell edit modes and for printing
		     select lists.
	      EDITOR If the value of this variable ends in emacs, gmacs, or vi and the VISUAL variable is not set, then the  corresponding  option
		     (see Special Command set below) will be turned on.
	      ENV    If  this  parameter is set, then parameter substitution is performed on the value to generate the pathname of the script that
		     will be executed when the shell is invoked.  (See Invocation below.)  This file is typically used for alias and function def-
		     initions.
	      FCEDIT The default editor name for the fc command.
	      FPATH  The search path for function definitions.	This path is searched when a function with the -u attribute is referenced and when
		     a command is not found.  If an executable file is found, then it is read and executed in the current environment.
	      IFS    Internal field separators, normally space, tab, and new-line that is used to separate command words which result from command
		     or  parameter  substitution and for separating words with the special command read.  The first character of the IFS parameter
		     is used to separate arguments for the $* substitution (See Quoting below).
	      HISTFILE
		     If this parameter is set when the shell is invoked, then the value is the pathname of the file that will be used to store the
		     command history.  (See Command re-entry below.)
	      HISTSIZE
		     If  this  parameter  is  set when the shell is invoked, then the number of previously entered commands that are accessible by
		     this shell will be greater than or equal to this number.  The default is 128.
	      HOME   The default argument (home directory) for the cd command.
	      LINES  If this variable is set, the value is used to determine the column length for printing select lists.  Select lists will print
		     vertically until about two-thirds of LINES lines are filled.
	      LOGNAME
		     The name of the user's login account, corresponding to the login name in the user database.
	      MAIL   If this parameter is set to the name of a mail file and the MAILPATH parameter is not set, then the shell informs the user of
		     arrival of mail in the specified file.
	      MAILCHECK
		     This variable specifies how often (in seconds) the shell will check for changes in the modification time of any of the  files
		     specified	by  the  MAILPATH or MAIL parameters.  The default value is 600 seconds.  When the time has elapsed the shell will
		     check before issuing the next prompt.
	      MAILPATH
		     A colon ( : ) separated list of file names.  If this parameter is set then the shell informs the user of any modifications to
		     the  specified files that have occurred within the last MAILCHECK seconds.  Each file name can be followed by a ?	and a mes-
		     sage that will be printed.  The message will undergo parameter substitution with the parameter, $_ defined as the name of the
		     file that has changed.  The default message is you have mail in $_.
	      PATH   The search path for commands (see Execution below).  The user may not change PATH if executing under (except in .profile ).
	      PS1    The  value  of  this parameter is expanded for parameter substitution to define the primary prompt string which by default is
		     ``$ ''.  The character !  in the primary prompt string is replaced by the command number (see Command Re-entry below).
	      PS2    Secondary prompt string, by default ``> ''.
	      PS3    Selection prompt string used within a select loop, by default ``#? ''.
	      PS4    The value of this parameter is expanded for parameter substitution and precedes each line of an execution trace.  If omitted,
		     the execution trace prompt is ``+ ''.
	      SHELL  The  pathname  of	the shell is kept in the environment.  At invocation, if the basename of this variable matches the pattern
		     *r*sh, then the shell becomes restricted.
	      TMOUT  If set to a value greater than zero, the shell will terminate if a command is not entered within  the  prescribed	number	of
		     seconds  after issuing the PS1 prompt.  (Note that the shell can be compiled with a maximum bound for this value which cannot
		     be exceeded.)
	      VISUAL If the value of this variable ends in emacs, gmacs, or vi then the corresponding option (see Special Command set below)  will
		     be turned on.

       The  shell gives default values to PATH, PS1, PS2, MAILCHECK, TMOUT and IFS, while HOME, SHELL ENV and MAIL are not set at all by the shell
       (although HOME is set by login(1)).  On some systems MAIL and SHELL are also set by login(1)).

   Blank Interpretation.
       After parameter and command substitution, the results of substitutions are scanned for the field separator characters ( those found in  IFS
       )  and  split into distinct arguments where such characters are found.  Explicit null arguments ("" or (fm(fm) are retained.  Implicit null
       arguments (those resulting from parameters that have no values) are removed.

   File Name Generation.
       Following substitution, each command word is scanned for the characters *, ?, and [ unless the -f option has been set.	If  one  of  these
       characters  appears  then  the word is regarded as a pattern.  The word is replaced with lexicographically sorted file names that match the
       pattern.  If no file name is found that matches the pattern, then the word is left unchanged.  When a pattern is used for file name genera-
       tion, the character .  at the start of a file name or immediately following a /, as well as the character / itself, must be matched explic-
       itly.  In other instances of pattern matching the / and .  are not treated specially.

	      *      Matches any string, including the null string.
	      ?      Matches any single character.
	      [...]  Matches any one of the enclosed characters.  A pair of characters separated by - matches any character lexically between  the
		     pair,  inclusive.	If the first character following the opening "[ " is a "! " then any character not enclosed is matched.  A
		     - can be included in the character set by putting it as the first or last character.
       A pattern-list is a list of one or more patterns separated by each other with a |.  Composite patterns can be formed with one  or  more	of
       the following:
	      ?(pattern-list)
		     Optionally matches any one of the given patterns.
	      *(pattern-list)
		     Matches zero or more occurrences of the given patterns.
	      +(pattern-list)
		     Matches one or more occurrences of the given patterns.
	      @(pattern-list)
		     Matches exactly one of the given patterns.
	      !(pattern-list)
		     Matches anything, except one of the given patterns.

   Quoting.
       Each  of the metacharacters listed above (See Definitions above) has a special meaning to the shell and causes termination of a word unless
       quoted.	A character may be quoted (that is, made to stand for itself) by preceding it with a .  The pair 
ew-line is ignored.  All char-
       acters  enclosed  between a pair of single quote marks (''), are quoted.  A single quote cannot appear within single quotes.  Inside double
       quote marks (""), parameter and command substitution occurs and  quotes the characters , `, ", and $.	The meaning of $* and $@ is  iden-
       tical  when  not  quoted  or  when used as a parameter assignment value or as a file name.  However, when used as a command argument, $* is
       equivalent to "$1d$2d...", where d is the first character of the IFS parameter, whereas $@ is equivalent to $1	"$2"  ....   Inside  grave
       quote marks  quotes the characters , and

       If the grave quotes occur within double quotes then  also quotes the character ".

       The special meaning of reserved words or aliases can be removed by quoting any character of the reserved word.  The recognition of function
       names or special command names listed below cannot be altered by quoting them.

   Arithmetic Evaluation.
       An ability to perform integer arithmetic is provided with the special command let.  Evaluations are performed using long arithmetic.   Con-
       stants  are of the form [base#]n where base is a decimal number between two and thirty-six representing the arithmetic base and n is a num-
       ber in that base.  If base is omitted then base 10 is used.

       An arithmetic expression uses the same syntax, precedence, and associativity of expression of the C language.  All the integral	operators,
       other  than  ++, --, ?:, and , are supported.  Named parameters can be referenced by name within an arithmetic expression without using the
       parameter substitution syntax.  When a named parameter is referenced, its value is evaluated as an arithmetic expression.

       An internal integer representation of a named parameter can be specified with the -i option of the  typeset  special  command.	Arithmetic
       evaluation  is  performed  on the value of each assignment to a named parameter with the -i attribute.  If you do not specify an arithmetic
       base, the first assignment to the parameter determines the arithmetic base.  This base is used when parameter substitution occurs.

       Since many of the arithmetic operators require quoting, an alternative form of the let command is provided.  For any command  which  begins
       with a ((, all the characters until a matching )) are treated as a quoted expression.  More precisely, ((...))  is equivalent to let "...".

   Prompting.
       When  used interactively, the shell prompts with the value of PS1 before reading a command.  If at any time a new-line is typed and further
       input is needed to complete a command, then the secondary prompt (that is, the value of PS2) is issued.

   Conditional Expressions.
       A conditional expression is used with the [[ compound command to test attributes of files and to compare strings.  Word splitting and  file
       name  generation  are  not  performed on the words between [[ and ]].  Each expression can be constructed from one or more of the following
       unary or binary expressions:
       -a file
	      True, if file exists.
       -b file
	      True, if file exists and is a block special file.
       -c file
	      True, if file exists and is a character special file.
       -d file
	      True, if file exists and is a directory.
       -f file
	      True, if file exists and is an ordinary file.
       -g file
	      True, if file exists and is has its setgid bit set.
       -k file
	      True, if file exists and is has its sticky bit set.
       -n string
	      True, if length of string is non-zero.
       -o option
	      True, if option named option is on.
       -p file
	      True, if file exists and is a fifo special file or a pipe.
       -r file
	      True, if file exists and is readable by current process.
       -s file
	      True, if file exists and has size greater than zero.
       -t fildes
	      True, if file descriptor number fildes is open and associated with a terminal device.
       -u file
	      True, if file exists and is has its setuid bit set.
       -w file
	      True, if file exists and is writable by current process.
       -x file
	      True, if file exists and is executable by current process.  If file exists and is a directory, then the current process has  permis-
	      sion to search in the directory.
       -z string
	      True, if length of string is zero.
       -L file
	      True, if file exists and is a symbolic link.
       -O file
	      True, if file exists and is owned by the effective user id of this process.
       -G file
	      True, if file exists and its group matches the effective group id of this process.
       -S file
	      True, if file exists and is a socket.
       file1 -nt file2
	      True, if file1 exists and is newer than file2.
       file1 -ot file2
	      True, if file1 exists and is older than file2.
       file1 -ef file2
	      True, if file1 and file2 exist and refer to the same file.
       string = pattern
	      True, if string matches pattern.
       string != pattern
	      True, if string does not match pattern.
       string1 < string2
	      True, if string1 comes before string2 based on ASCII value of their characters.
       string1 > string2
	      True, if string1 comes after string2 based on ASCII value of their characters.
       exp1 -eq exp2
	      True, if exp1 is equal to exp2.
       exp1 -ne exp2
	      True, if exp1 is not equal to exp2.
       exp1 -lt exp2
	      True, if exp1 is less than exp2.
       exp1 -gt exp2
	      True, if exp1 is greater than exp2.
       exp1 -le exp2
	      True, if exp1 is less than or equal to exp2.
       exp1 -ge exp2
	      True, if exp1 is greater than or equal to exp2.

       In  each  of  the  above expressions, if file is of the form /dev/fd/n, where n is an integer, then the test applied to the open file whose
       descriptor number is n.

       A compound expression can be constructed from these primitives by using any of the following, listed in decreasing order of precedence.
       (expression)
	      True, if expression is true.  Used to group expressions.
       ! expression
	      True if expression is false.
       expression1 && expression2
	      True, if expression1 and expression2 are both true.
       expression1 || expression2
	      True, if either expression1 or expression2 is true.

   Input/output.
       Before a command is executed, its input and output may be redirected using a special notation interpreted by the shell.	The following  may
       appear anywhere in a simple-command or may precede or follow a command and are not passed on to the invoked command.  Command and parameter
       substitution occurs before word or digit is used except as noted below.	File name generation occurs only if the pattern matches  a  single
       file and blank interpretation is not performed.

       <word	     Use file word as standard input (file descriptor 0).

       >word	     Use  file	word  as standard output (file descriptor 1).  If the file does not exist then it is created.  If the file exists,
		     and the noclobber option is on, this causes an error; otherwise, it is truncated to zero length.

       >|word	     Sames as >, except that it overrides the noclobber option.

       >>word	     Use file word as standard output.	If the file exists then output is appended to it (by first seeking  to	the  end-of-file);
		     otherwise, the file is created.

       <>word	     Open file word for reading and writing as standard input.

       <<[-]word     The shell input is read up to a line that is the same as word, or to an end-of-file.  No parameter substitution, command sub-
		     stitution or file name generation is performed on word.  The resulting document, called a here-document, becomes the standard
		     input.   If any character of word is quoted, then no interpretation is placed upon the characters of the document; otherwise,
		     parameter and command substitution occurs, 
ew-line is ignored, and  must be used to quote the characters  ,  $,  and  the
		     first character of word.  If - is appended to <<, then all leading tabs are stripped from word and from the document.

       <&digit	     The standard input is duplicated from file descriptor digit (see dup(2)).	Similarly for the standard output using >& digit.

       <&-	     The standard input is closed.  Similarly for the standard output using >&-.

       <&p	     The input from the co-process is moved to standard input.

       >&p	     The output to the co-process is moved to standard output.

       If  one	of  the  above	is preceded by a digit, then the file descriptor number referred to is that specified by the digit (instead of the
       default 0 or 1).  For example:

	      ... 2>&1

       means file descriptor 2 is to be opened for writing as a duplicate of file descriptor 1.

       The order in which redirections are specified is significant.  The shell evaluates each redirection in terms of the (file descriptor, file)
       association at the time of evaluation.  For example:

	      ... 1>fname 2>&1

       first  associates  file descriptor 1 with file fname.  It then associates file descriptor 2 with the file associated with file descriptor 1
       (that is, fname).  If the order of redirections were reversed, file descriptor 2 would be  associated  with  the  terminal  (assuming  file
       descriptor 1 had been) and then file descriptor 1 would be associated with file fname.

       If  a  command is followed by & and job control is not active, then the default standard input for the command is the empty file /dev/null.
       Otherwise, the environment for the execution of a command contains the file descriptors of the invoking shell as modified  by  input/output
       specifications.

   Environment.
       The  environment  (see environ(7)) is a list of name-value pairs that is passed to an executed program in the same way as a normal argument
       list.  The names must be identifiers and the values are character strings.  The shell interacts with the environment in several	ways.	On
       invocation,  the  shell scans the environment and creates a parameter for each name found, giving it the corresponding value and marking it
       export .  Executed commands inherit the environment.  If the user modifies the values of these parameters or creates new  ones,	using  the
       export  or  typeset  -x commands they become part of the environment.  The environment seen by any executed command is thus composed of any
       name-value pairs originally inherited by the shell, whose values may be modified by the current shell, plus any	additions  which  must	be
       noted in export or typeset -x commands.

       The  environment  for  any simple-command or function may be augmented by prefixing it with one or more parameter assignments.  A parameter
       assignment argument is a word of the form identifier=value.  Thus:

	      TERM=450 cmd args 		 and
	      (export TERM; TERM=450; cmd args)

       are equivalent (as far as the above execution of cmd is concerned).

       If the -k flag is set, all parameter assignment arguments are placed in the environment, even if they occur after the  command  name.   The
       following first prints a=b c and then c:

	      echo a=b c
	      set -k
	      echo a=b c
       This  feature  is intended for use with scripts written for early versions of the shell and its use in new scripts is strongly discouraged.
       It is likely to disappear someday.

   Functions.
       The function reserved word, described in the Commands section above, is used to define shell functions.	Shell functions are  read  in  and
       stored  internally.  Alias names are resolved when the function is read.  Functions are executed like commands with the arguments passed as
       positional parameters.  (See Execution below).

       Functions execute in the same process as the caller and share all files and present working directory with the caller.  Traps caught by the
       caller  are  reset  to their default action inside the function.  A trap condition that is not caught or ignored by the function causes the
       function to terminate and the condition to be passed on to the caller.  A trap on EXIT set inside a function is executed after the function
       completes  in  the environment of the caller.  Ordinarily, variables are shared between the calling program and the function.  However, the
       typeset special command used within a function defines local variables whose scope includes the	current  function  and	all  functions	it
       calls.

       The special command return is used to return from function calls.  Errors within functions return control to the caller.

       Function identifiers can be listed with the -f or +f option of the typeset special command.  The text of functions will also be listed with
       -f.  Function can be undefined with the -f option of the unset special command.

       Ordinarily, functions are unset when the shell executes a shell script.	The -xf option of the typeset command  allows  a  function  to	be
       exported  to scripts that are executed without a separate invocation of the shell.  Functions that need to be defined across separate invo-
       cations of the shell should be specified in the ENV file with the -xf option of typeset

   Jobs.
       If the monitor option of the set command is turned on, an interactive shell associates a job with each pipeline.  It keeps a table of  cur-
       rent  jobs,  printed  by  the jobs command, and assigns them small integer numbers.  When a job is started asynchronously with &, the shell
       prints a line which looks like:

	    [1] 1234

       indicating that the job which was started asynchronously was job number 1 and had one (top-level) process, whose process id was 1234.

       This paragraph and the next require features that are not in all versions of the UNIX operating system and may not apply.  If you are  run-
       ning  a	job and wish to do something else you may hit the key ^Z (control-Z) which sends a STOP signal to the current job.  The shell will
       then normally indicate that the job has been `Stopped', and print another prompt.  You can then manipulate the state of this  job,  putting
       it  in  the  background with the bg command, or run some other commands and then eventually bring the job back into the foreground with the
       foreground command fg.  A ^Z takes effect immediately and is like an interrupt in that pending output and unread input are  discarded  when
       it is typed.

       A job being run in the background will stop if it tries to read from the terminal.  Background jobs are normally allowed to produce output,
       but this can be disabled by giving the command ``stty tostop''.	If you set this tty option, then background jobs will stop when  they  try
       to produce output like they do when they try to read input.

       There  are  several  ways to refer to jobs in the shell.  A job can be referred to by the process id of any process of the job or by one of
       the following:
       %number
	      The job with the given number.
       %string
	      Any job whose command line begins with string.
       %?string
	      Any job whose command line contains string.
       %%     Current job.
       %+     Equivalent to %%.
       %-     Previous job.

       This shell learns immediately whenever a process changes state.	It normally informs you whenever a job becomes blocked so that no  further
       progress is possible, but only just before it prints a prompt.  This is done so that it does not otherwise disturb your work.

       When the monitor mode is on, each background job that completes triggers any trap set for CHLD.

       When  you  try to leave the shell while jobs are running or stopped, you will be warned that `You have stopped(running) jobs.'  You may use
       the jobs command to see what they are.  If you do this or immediately try to exit again, the shell will not warn you a second time, and the
       stopped jobs will be terminated.

   Signals.
       The  INT  and QUIT signals for an invoked command are ignored if the command is followed by & and job monitor option is not active.  Other-
       wise, signals have the values inherited by the shell from its parent (but see also the trap command below).

   Execution.
       Each time a command is executed, the above substitutions are carried out.  If the command name matches one of the Special  Commands  listed
       below,  it  is  executed  within the current shell process.  Next, the command name is checked to see if it matches one of the user defined
       functions.  If it does, the positional parameters are saved and then reset to the arguments of the function call.  When the  function  com-
       pletes  or  issues a return, the positional parameter list is restored and any trap set on EXIT within the function is executed.  The value
       of a function is the value of the last command executed.  A function is also executed in the current shell process.  If a command  name	is
       not a special command or a user defined function, a process is created and an attempt is made to execute the command via exec(2).

       The  shell parameter PATH defines the search path for the directory containing the command.  Alternative directory names are separated by a
       colon (:).  The default path is /bin:/usr/bin: (specifying /bin, /usr/bin, and the current directory in that order).  The current directory
       can  be specified by two or more adjacent colons, or by a colon at the beginning or end of the path list.  If the command name contains a /
       then the search path is not used.  Otherwise, each directory in the path is searched for an executable file.  If the file has execute  per-
       mission	but is not a directory or an a.out file, it is assumed to be a file containing shell commands.	A sub-shell is spawned to read it.
       All non-exported aliases, functions, and named parameters are removed in this case.  If the shell command file doesn't  have  read  permis-
       sion,  or  if the setuid and/or setgid bits are set on the file, then the shell executes an agent whose job it is to set up the permissions
       and execute the shell with the shell command file passed down as an open file.  A parenthesized command is executed in a sub-shell  without
       removing non-exported quantities.

   Command Re-entry.
       The text of the last HISTSIZE (default 128) commands entered from a terminal device is saved in a history file.	The file $HOME/.sh_history
       is used if the HISTFILE variable is not set or is not writable.	A shell can access the commands of all interactive shells  which  use  the
       same  named  HISTFILE.	The  special  command  fc is used to list or edit a portion of this file.  The portion of the file to be edited or
       listed can be selected by number or by giving the first character or characters of the command.	A single command or range of commands  can
       be  specified.	If you do not specify an editor program as an argument to fc then the value of the parameter FCEDIT is used.  If FCEDIT is
       not defined then /bin/ed is used.  The edited command(s) is printed and re-executed upon leaving the editor.  The editor name - is used	to
       skip  the editing phase and to re-execute the command.  In this case a substitution parameter of the form old=new can be used to modify the
       command before execution.  For example, if r is aliased to 'fc -e -' then typing `r bad=good c' will re-execute	the  most  recent  command
       which starts with the letter c, replacing the first occurrence of the string bad with the string good.

   In-line Editing Options
       Normally, each command line entered from a terminal device is simply typed followed by a new-line (`RETURN' or `LINE FEED').  If either the
       emacs, gmacs, or vi option is active, the user can edit the command line.  To be in either  of  these  edit  modes  set	the  corresponding
       option.	 An editing option is automatically selected each time the VISUAL or EDITOR variable is assigned a value ending in either of these
       option names.

       The editing features require that the user's terminal accept `RETURN' as carriage return without line feed and  that  a	space  (` ')  must
       overwrite  the  current	character  on the screen.  ADM terminal users should set the "space - advance" switch to `space'.  Hewlett-Packard
       series 2621 terminal users should set the straps to `bcGHxZ etX'.

       The editing modes implement a concept where the user is looking through a window at the current line.  The window width	is  the  value	of
       COLUMNS	if it is defined, otherwise 80.  If the line is longer than the window width minus two, a mark is displayed at the end of the win-
       dow to notify the user.	As the cursor moves and reaches the window boundaries the window will be centered about the cursor.  The mark is a
       > (<, *) if the line extends on the right (left, both) side(s) of the window.

       The  search commands in each edit mode provide access to the history file.  Only strings are matched, not patterns, although a leading ^ in
       the string restricts the match to begin at the first character in the line.

   Emacs Editing Mode
       This mode is entered by enabling either the emacs or gmacs option.  The only difference between these two modes is the way they handle  ^T.
       To  edit,  the  user  moves  the cursor to the point needing correction and then inserts or deletes characters or words as needed.  All the
       editing commands are control characters or escape sequences.  The notation for control characters is caret ( ^ ) followed by the character.
       For example, ^F is the notation for control F.  This is entered by depressing `f' while holding down the `CTRL' (control) key.  The `SHIFT'
       key is not depressed.  (The notation ^?	indicates the DEL (delete) key.)

       The notation for escape sequences is M- followed by a character.  For example, M-f (pronounced Meta f) is entered by depressing ESC  (ascii
       033) followed by `f'.  (M-F would be the notation for ESC followed by `SHIFT' (capital) `F'.)

       All  edit commands operate from any place on the line (not just at the beginning).  Neither the "RETURN" nor the "LINE FEED" key is entered
       after edit commands except when noted.

       ^F	 Move cursor forward (right) one character.
       M-f	 Move cursor forward one word.	(The emacs editor's idea of a word is a string of characters consisting of  only  letters,  digits
		 and underscores.)
       ^B	 Move cursor backward (left) one character.
       M-b	 Move cursor backward one word.
       ^A	 Move cursor to start of line.
       ^E	 Move cursor to end of line.
       ^]char	 Move cursor forward to character char on current line.
       M-^]char  Move cursor back to character char on current line.
       ^X^X	 Interchange the cursor and mark.
       erase	 (User defined erase character as defined by the stty(1) command, usually ^H or #.)  Delete previous character.
       ^D	 Delete current character.
       M-d	 Delete current word.
       M-^H	 (Meta-backspace) Delete previous word.
       M-h	 Delete previous word.
       M-^?	 (Meta-DEL) Delete previous word (if your interrupt character is ^?  (DEL, the default) then this command will not work).
       ^T	 Transpose current character with next character in emacs mode.  Transpose two previous characters in gmacs mode.
       ^C	 Capitalize current character.
       M-c	 Capitalize current word.
       M-l	 Change the current word to lower case.
       ^K	 Delete  from the cursor to the end of the line.  If preceded by a numerical parameter whose value is less than the current cursor
		 position, then delete from given position up to the cursor.  If preceded by a numerical parameter whose value is greater than the
		 current cursor position, then delete from cursor up to given cursor position.
       ^W	 Kill from the cursor to the mark.
       M-p	 Push the region from the cursor to the mark on the stack.
       kill	 (User	defined kill character as defined by the stty command, usually ^G or @.)  Kill the entire current line.  If two kill char-
		 acters are entered in succession, all kill characters from then on cause a line feed (useful when using paper terminals).
       ^Y	 Restore last item removed from line. (Yank item back to the line.)
       ^L	 Line feed and print current line.
       ^@	 (Null character) Set mark.
       M-space	 (Meta space) Set mark.
       ^J	 (New line) Execute the current line.
       ^M	 (Return) Execute the current line.
       eof	 End-of-file character, normally ^D, is processed as an End-of-file only if the current line is null.
       ^P	 Fetch previous command.  Each time ^P is entered the previous command back in time is accessed.  Moves back one line when not	on
		 the first line of a multi-line command.
       M-<	 Fetch the least recent (oldest) history line.
       M->	 Fetch the most recent (youngest) history line.
       ^N	 Fetch next command line.  Each time ^N is entered the next command line forward in time is accessed.
       ^Rstring  Reverse  search  history  for a previous command line containing string.  If a parameter of zero is given, the search is forward.
		 String is terminated by a "RETURN" or "NEW LINE".  If string is preceded by a ^, the matched line must  begin	with  string.	If
		 string  is  omitted,  then the next command line containing the most recent string is accessed.  In this case a parameter of zero
		 reverses the direction of the search.
       ^O	 Operate - Execute the current line and fetch the next line relative to current line from the history file.
       M-digits  (Escape) Define numeric parameter, the digits are taken as a parameter to the next command.  The commands that accept a parameter
		 are ^F, ^B, erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-., M-^], M-_, M-b, M-c, M-d, M-f, M-h M-l and M-^H.
       M-letter  Soft-key  -  Your alias list is searched for an alias by the name _letter and if an alias of this name is defined, its value will
		 be inserted on the input queue.  The letter must not be one of the above meta-functions.  M-]letter Soft-key - Your alias list is
		 searched  for	an  alias  by  the  name __letter and if an alias of this name is defined, its value will be inserted on the input
		 queue.  The can be used to program functions keys on many terminals.
       M-.	 The last word of the previous command is inserted on the line.  If preceded by a numeric parameter, the value of  this  parameter
		 determines which word to insert rather than the last word.
       M-_	 Same as M-..
       M-*	 Attempt file name generation on the current word.  An asterisk is appended if the word doesn't match any file or contain any spe-
		 cial pattern characters.
       M-ESC	 File name completion.	Replaces the current word with the longest common prefix of all filenames matching the current	word  with
		 an  asterisk appended.  If the match is unique, a / is appended if the file is a directory and a space is appended if the file is
		 not a directory.
       M-=	 List files matching current word pattern if an asterisk were appended.
       ^U	 Multiply parameter of next command by 4.
       	 Escape next character.  Editing characters, the user's erase, kill and interrupt (normally ^?)  characters may be  entered  in  a
		 command line or in a search string if preceded by a .  The  removes the next character's editing features (if any).
       ^V	 Display version of the shell.
       M-Inserta at the beginning of the line and execute it.  This causes a comment to be inserted in the history file.

   Vi Editing Mode
       There  are two typing modes.  Initially, when you enter a command you are in the input mode.  To edit, the user enters control mode by typ-
       ing ESC ( 033 ) and moves the cursor to the point needing correction and then inserts or deletes characters or words as needed.	Most  con-
       trol commands accept an optional repeat count prior to the command.

       When  in  vi mode on most systems, canonical processing is initially enabled and the command will be echoed again if the speed is 1200 baud
       or greater and it contains any control characters or less than one second has elapsed since the prompt was printed.  The ESC character ter-
       minates	canonical  processing  for the remainder of the command and the user can then modify the command line.	This scheme has the advan-
       tages of canonical processing with the type-ahead echoing of raw mode.

       If the option viraw is also set, the terminal will always have canonical processing disabled.  This mode is implicit for  systems  that	do
       not support two alternate end of line delimiters, and may be helpful for certain terminals.

   Input Edit Commands
	      By default the editor is in input mode.
	      erase	(User defined erase character as defined by the stty command, usually ^H or #.)  Delete previous character.
	      ^W	Delete the previous blank separated word.
	      ^D	Terminate the shell.
	      ^V	Escape	next  character.  Editing characters, the user's erase or kill characters may be entered in a command line or in a
			search string if preceded by a ^V.  The ^V removes the next character's editing features (if any).
	       	Escape the next erase or kill character.
   Motion Edit Commands
	      These commands will move the cursor.
	      [count]l	Cursor forward (right) one character.
	      [count]w	Cursor forward one alpha-numeric word.
	      [count]W	Cursor to the beginning of the next word that follows a blank.
	      [count]e	Cursor to end of word.
	      [count]E	Cursor to end of the current blank delimited word.
	      [count]h	Cursor backward (left) one character.
	      [count]b	Cursor backward one word.
	      [count]B	Cursor to preceding blank separated word.
	      [count]|	Cursor to column count.
	      [count]fc Find the next character c in the current line.
	      [count]Fc Find the previous character c in the current line.
	      [count]tc Equivalent to f followed by h.
	      [count]Tc Equivalent to F followed by l.
	      [count];	Repeats count times, the last single character find command, f, F, t, or T.
	      [count],	Reverses the last single character find command count times.
	      0 	Cursor to start of line.
	      ^ 	Cursor to first non-blank character in line.
	      $ 	Cursor to end of line.
   Search Edit Commands
	      These commands access your command history.
	      [count]k	Fetch previous command.  Each time k is entered the previous command back in time is accessed.
	      [count]-	Equivalent to k.
	      [count]j	Fetch next command.  Each time j is entered the next command forward in time is accessed.
	      [count]+	Equivalent to j.
	      [count]G	The command number count is fetched.  The default is the least recent history command.
	      /string	Search backward through history for a previous	command  containing  string.   String  is  terminated  by  a  "RETURN"	or
			"NEW LINE".  If string is preceded by a ^, the matched line must begin with string.  If string is null the previous string
			will be used.
	      ?string	Same as / except that search will be in the forward direction.
	      n 	Search for next match of the last pattern to / or ?  commands.
	      N 	Search for next match of the last pattern to / or ?, but in reverse direction.	Search history for the string  entered	by
			the previous / command.
   Text Modification Edit Commands
	      These commands will modify the line.
	      a 	Enter input mode and enter text after the current character.
	      A 	Append text to the end of the line.  Equivalent to $a.
	      [count]cmotion
	      c[count]motion
			Delete current character through the character that motion would move the cursor to and enter input mode.  If motion is c,
			the entire line will be deleted and input mode entered.
	      C 	Delete the current character through the end of line and enter input mode.  Equivalent to c$.
	      S 	Equivalent to cc.
	      D 	Delete the current character through the end of line.  Equivalent to d$.
	      [count]dmotion
	      d[count]motion
			Delete current character through the character that motion would move to.  If motion is  d  ,  the  entire  line  will	be
			deleted.
	      i 	Enter input mode and insert text before the current character.
	      I 	Insert text before the beginning of the line.  Equivalent to 0i.
	      [count]P	Place the previous text modification before the cursor.
	      [count]p	Place the previous text modification after the cursor.
	      R 	Enter input mode and replace characters on the screen with characters you type overlay fashion.
	      [count]rc Replace the count character(s) starting at the current cursor position with c, and advance the cursor.
	      [count]x	Delete current character.
	      [count]X	Delete preceding character.
	      [count].	Repeat the previous text modification command.
	      [count]~	Invert the case of the count character(s) starting at the current cursor position and advance the cursor.
	      [count]_	Causes	the  count  word of the previous command to be appended and input mode entered.  The last word is used if count is
			omitted.
	      * 	Causes an * to be appended to the current word and file name generation attempted.  If no match is  found,  it	rings  the
			bell.  Otherwise, the word is replaced by the matching pattern and input mode is entered.
	       	Filename  completion.  Replaces the current word with the longest common prefix of all filenames matching the current word
			with an asterisk appended.  If the match is unique, a / is appended if the file is a directory and a space is appended	if
			the file is not a directory.
   Other Edit Commands
	      Miscellaneous commands.
	      [count]ymotion
	      y[count]motion
			Yank  current  character through character that motion would move the cursor to and puts them into the delete buffer.  The
			text and cursor are unchanged.
	      Y 	Yanks from current position to end of line.  Equivalent to y$.
	      u 	Undo the last text modifying command.
	      U 	Undo all the text modifying commands performed on the line.
	      [count]v	Returns the command fc -e ${VISUAL:-${EDITOR:-vi}} count in the input buffer.  If count is omitted, then the current  line
			is used.
	      ^L	Line feed and print current line.  Has effect only in control mode.
	      ^J	(New line) Execute the current line, regardless of mode.
	      ^M	(Return) Execute the current line, regardless of mode.
	      Sends the line after
			inserting  a  in  front of the line.  Useful for causing the current line to be inserted in the history without being exe-
			cuted.
	      = 	List the file names that match the current word if an asterisk were appended it.
	      @letter	Your alias list is searched for an alias by the name _letter and if an alias of this name is defined, its  value  will	be
			inserted on the input queue for processing.

   Special Commands.
       The  following  simple-commands are executed in the shell process.  Input/Output redirection is permitted.  Unless otherwise indicated, the
       output is written on file descriptor 1 and the exit status, when there is no syntax error, is zero.  Commands that are preceded by  one	or
       two - are treated specially in the following ways:
       1.     Parameter assignment lists preceding the command remain in effect when the command completes.
       2.     I/O redirections are processed after parameter assignments.
       3.     Errors cause a script that contains them to abort.
       4.     Words,  following  a  command preceded by -- that are in the format of a parameter assignment, are expanded with the same rules as a
	      parameter assignment.  This means that tilde substitution is performed after the = sign and word splitting and file name	generation
	      are not performed.

       - : [ arg ... ]
	      The command only expands parameters.

       - . file [ arg ... ]
	      Read  the  complete  file  then  execute the commands.  The commands are executed in the current Shell environment.  The search path
	      specified by PATH is used to find the directory containing file.	If any arguments arg are given, they become the positional parame-
	      ters.  Otherwise the positional parameters are unchanged.  The exit status is the exit status of the last command executed.

       -- alias [ -tx ]  [ name[ =value  ] ] ...
	      Alias  with  no  arguments  prints the list of aliases in the form name=value on standard output.  An alias is defined for each name
	      whose value is given.  A trailing space in value causes the next word to be checked for alias substitution.  The -t flag is used	to
	      set and list tracked aliases.  The value of a tracked alias is the full pathname corresponding to the given name.  The value becomes
	      undefined when the value of PATH is reset but the aliases remained tracked.  Without the -t flag, for each name in the argument list
	      for  which no value is given, the name and value of the alias is printed.  The -x flag is used to set or print exported aliases.	An
	      exported alias is defined for scripts invoked by name.  The exit status is non-zero if a name is given, but no value, for  which	no
	      alias has been defined.

       bg [ job... ]
	      This  command  is only on systems that support job control.  Puts each specified job into the background.  The current job is put in
	      the background if job is not specified.  See Jobs for a description of the format of job.

       - break [ n ]
	      Exit from the enclosing for while until or select loop, if any.  If n is specified then break n levels.

       - continue [ n ]
	      Resume the next iteration of the enclosing for while until or select loop.  If n is specified then  resume  at  the  n-th  enclosing
	      loop.

       cd [ arg ]
       cd old new
	      This  command  can be in either of two forms.  In the first form it changes the current directory to arg.  If arg is - the directory
	      is changed to the previous directory.  The shell parameter HOME is the default arg.  The parameter PWD is set to the current  direc-
	      tory.   The  shell parameter CDPATH defines the search path for the directory containing arg.  Alternative directory names are sepa-
	      rated by a colon (:).  The default path is <null> (specifying the current directory).  Note that the current directory is  specified
	      by  a  null  path  name, which can appear immediately after the equal sign or between the colon delimiters anywhere else in the path
	      list.  If arg begins with a / then the search path is not used.  Otherwise, each directory in the path is searched for arg.

       The second form of cd substitutes the string new for the string old in the current directory name, PWD and tries  to  change  to  this  new
       directory.

       The cd command may not be executed by

       echo [ arg ... ]
	      See echo(1) for usage and description.

       - eval [ arg ... ]
	      The arguments are read as input to the shell and the resulting command(s) executed.

       - exec [ arg ... ]
	      If  arg  is  given,  the	command  specified  by	the  arguments	is executed in place of this shell without creating a new process.
	      Input/output arguments may appear and affect the current process.  If no arguments are given the effect of this command is to modify
	      file  descriptors as prescribed by the input/output redirection list.  In this case, any file descriptor numbers greater than 2 that
	      are opened with this mechanism are closed when invoking another program.

       - exit [ n ]
	      Causes the shell to exit with the exit status specified by n.  If n is omitted then the exit status is that of the last command exe-
	      cuted.   An  end-of-file	will also cause the shell to exit except for a shell which has the ignoreeof option (See set below) turned
	      on.

       -- export [ name[=value] ] ...
	      The given names are marked for automatic export to the environment of subsequently-executed commands.

       fc [ -e ename  ] [ -nlr ] [ first [ last ] ]
       fc -e - [ old=new ] [ command ]
	      In the first form, a range of commands from first to last is selected from the last HISTSIZE commands that were typed at the  termi-
	      nal.   The arguments first and last may be specified as a number or as a string.	A string is used to locate the most recent command
	      starting with the given string.  A negative number is used as an offset to the current command number.  If the flag -l, is selected,
	      the commands are listed on standard output.  Otherwise, the editor program ename is invoked on a file containing these keyboard com-
	      mands.  If ename is not supplied, then the value of the parameter FCEDIT (default /bin/ed) is used as the editor.  When  editing	is
	      complete,  the edited command(s) is executed.  If last is not specified then it will be set to first.  If first is not specified the
	      default is the previous command for editing and -16 for listing.	The flag -r reverses the order of the commands	and  the  flag	-n
	      suppresses command numbers when listing.	In the second form the command is re-executed after the substitution old=new is performed.

       fg [ job... ]
	      This  command is only on systems that support job control.  Each job specified is brought to the foreground.  Otherwise, the current
	      job is brought into the foreground.  See Jobs for a description of the format of job.

       getopts optstring name [ arg ... ]
	      Checks arg for legal options.  If arg is omitted, the positional parameters are used.  An option argument begins with a +  or  a	-.
	      An  option  not  beginning with + or - or the argument -- ends the options.  optstring contains the letters that getopts recognizes.
	      If a letter is followed by a :, that option is expected to have an argument.  The options can be	separated  from  the  argument	by
	      blanks.

       getopts	places	the  next option letter it finds inside variable name each time it is invoked with a + prepended when arg begins with a +.
       The index of the next arg is stored in OPTIND.  The option argument, if any, gets stored in OPTARG.

       A leading : in optstring causes getopts to store the letter of an invalid option in OPTARG, and to set name to ?  for an unknown option and
       to  :  when  a required option is missing.  Otherwise, getopts prints an error message.	The exit status is non-zero when there are no more
       options.

       jobs [ -lnp ] [ job ... ]
	      Lists information about each given job; or all active jobs if job is omitted.  The -l flag lists process ids in addition to the nor-
	      mal  information.   The  -n  flag  only  displays jobs that have stopped or exited since last notified.  The -p flag causes only the
	      process group to be listed.  See Jobs for a description of the format of job.

       kill [ -sig ] job ...
       kill -l
	      Sends either the TERM (terminate) signal or the specified signal to the specified jobs or processes.  Signals are  either  given	by
	      number  or  by  names (as given in /usr/include/signal.h, stripped of the prefix ``SIG'').  If the signal being sent is TERM (termi-
	      nate) or HUP (hangup), then the job or process will be sent a CONT (continue) signal if it is stopped.  The  argument  job  can  the
	      process  id  of  a process that is not a member of one of the active jobs.  See Jobs for a description of the format of job.  In the
	      second form, kill -l, the signal numbers and names are listed.

       let arg ...
	      Each arg is a separate arithmetic expression to be evaluated.  See Arithmetic Evaluation above,  for  a  description  of	arithmetic
	      expression evaluation.

       The exit status is 0 if the value of the last expression is non-zero, and 1 otherwise.

       - newgrp [ arg ... ]
	      Equivalent to exec /bin/newgrp arg ....

       print [ -Rnprsu[n ] ] [ arg ... ]
	      The  shell  output  mechanism.   With  no  flags	or  with flag - or -- the arguments are printed on standard output as described by
	      echo(1).	In raw mode, -R or -r, the escape conventions of echo are ignored.  The -R option will print all subsequent arguments  and
	      options  other  than  -n.   The -p option causes the arguments to be written onto the pipe of the process spawned with |& instead of
	      standard output.	The -s option causes the arguments to be written onto the history file instead of standard output.   The  -u  flag
	      can be used to specify a one digit file descriptor unit number n on which the output will be placed.  The default is 1.  If the flag
	      -n is used, no new-line is added to the output.

       pwd    Equivalent to print -r - $PWD

       read [ -prsu[ n ] ] [ name?prompt ] [ name ... ]
	      The shell input mechanism.  One line is read and is broken up into fields using the characters in IFS as separators.  In	raw  mode,
	      -r, a  at the end of a line does not signify line continuation.	The first field is assigned to the first name, the second field to
	      the second name, etc., with leftover fields assigned to the last name.  The -p option causes the input line to  be  taken  from  the
	      input  pipe of a process spawned by the shell using |&.  If the -s flag is present, the input will be saved as a command in the his-
	      tory file.  The flag -u can be used to specify a one digit file descriptor unit to read from.  The file  descriptor  can	be  opened
	      with  the  exec special command.	The default value of n is 0.  If name is omitted then REPLY is used as the default name.  The exit
	      status is 0 unless an end-of-file is encountered.  An end-of-file with the -p option causes cleanup for this process so that another
	      can be spawned.  If the first argument contains a ?, the remainder of this word is used as a prompt on standard error when the shell
	      is interactive.  The exit status is 0 unless an end-of-file is encountered.

       -- readonly [ name[=value] ] ...
	      The given names are marked readonly and these names cannot be changed by subsequent assignment.

       - return [ n ]
	      Causes a shell function to return to the invoking script with the return status specified by n.  If n is	omitted  then  the  return
	      status is that of the last command executed.  If return is invoked while not in a function or a .  script, then it is the same as an
	      exit.

       set [ +-aefhkmnopstuvx ] [ +-o option ]... [ +-A name ]	[ arg ... ]
	      The flags for this command have meaning as follows:
	      -A      Array assignment.  Unset the variable name and assign values sequentially from the list arg.  If +A is  used,  the  variable
		      name is not unset first.
	      -a      All subsequent parameters that are defined are automatically exported.
	      -e      If  a  command has a non-zero exit status, execute the ERR trap, if set, and exit.  This mode is disabled while reading pro-
		      files.
	      -f      Disables file name generation.
	      -h      Each command becomes a tracked alias when first encountered.
	      -k      All parameter assignment arguments are placed in the environment for a command, not just	those  that  precede  the  command
		      name.
	      -m      Background  jobs	will run in a separate process group and a line will print upon completion.  The exit status of background
		      jobs is reported in a completion message.  On systems with job control, this flag is turned on automatically for interactive
		      shells.
	      -n      Read commands and check them for syntax errors, but do not execute them.	Ignored for interactive shells.
	      -o      The following argument can be one of the following option names:
		      allexport
			      Same as -a.
		      errexit Same as -e.
		      bgnice  All background jobs are run at a lower priority.	This is the default mode.
		      emacs   Puts you in an emacs style in-line editor for command entry.
		      gmacs   Puts you in a gmacs style in-line editor for command entry.
		      ignoreeof
			      The shell will not exit on end-of-file.  The command exit must be used.
		      keyword Same as -k.
		      markdirs
			      All directory names resulting from file name generation have a trailing / appended.
		      monitor Same as -m.
		      noclobber
			      Prevents redirection > from truncating existing files.  Require >| to truncate a file when turned on.
		      noexec  Same as -n.
		      noglob  Same as -f.
		      nolog   Do not save function definitions in history file.
		      nounset Same as -u.
		      privileged
			      Same as -p.
		      verbose Same as -v.
		      trackall
			      Same as -h.
		      vi      Puts  you  in  insert  mode  of a vi style in-line editor until you hit escape character 033.  This puts you in move
			      mode.  A return sends the line.
		      viraw   Each character is processed as it is typed in vi mode.
		      xtrace  Same as -x.
		      If no option name is supplied then the current option settings are printed.
	      -p      Disables processing of the $HOME/.profile file and uses the file /etc/suid_profile instead of the ENV file.  This mode is on
		      whenever	the  effective uid (gid) is not equal to the real uid (gid).  Turning this off causes the effective uid and gid to
		      be set to the real uid and gid.
	      -s      Sort the positional parameters lexicographically.
	      -t      Exit after reading and executing one command.
	      -u      Treat unset parameters as an error when substituting.
	      -v      Print shell input lines as they are read.
	      -x      Print commands and their arguments as they are executed.
	      -       Turns off -x and -v flags and stops examining arguments for flags.
	      --      Do not change any of the flags; useful in setting $1 to a value beginning with -.  If no arguments follow this flag then the
		      positional parameters are unset.

	      Using  + rather than - causes these flags to be turned off.  These flags can also be used upon invocation of the shell.  The current
	      set of flags may be found in $-.	Unless -A is specified, the remaining arguments are positional parameters  and	are  assigned,	in
	      order,  to  $1 $2 ....  If no arguments are given then the names and values of all named parameters are printed on the standard out-
	      put.  If the only argument is +, the names of all named parameters are printed.

       - shift [ n ]
	      The positional parameters from $n+1 ...  are renamed $1 ... , default n is 1.  The parameter n can be any arithmetic expression that
	      evaluates to a non-negative number less than or equal to $#.

       - times
	      Print the accumulated user and system times for the shell and for processes run from the shell.

       - trap [ arg ] [ sig ] ...
	      arg is a command to be read and executed when the shell receives signal(s) sig.  (Note that arg is scanned once when the trap is set
	      and once when the trap is taken.)  Each sig can be given as a number or as the name of the signal.  Trap commands  are  executed	in
	      order  of  signal  number.  Any attempt to set a trap on a signal that was ignored on entry to the current shell is ineffective.	If
	      arg is omitted or is -, then all trap(s) sig are reset to their original values.	If arg is the null  string  then  this	signal	is
	      ignored by the shell and by the commands it invokes.  If sig is ERR then arg will be executed whenever a command has a non-zero exit
	      status.  sig is DEBUG then arg will be executed after each command.  If sig is 0 or EXIT and the trap statement is  executed  inside
	      the  body  of a function, then the command arg is executed after the function completes.	If sig is 0 or EXIT for a trap set outside
	      any function then the command arg is executed on exit from the shell.  The trap command with no arguments prints a list of  commands
	      associated with each signal number.

       -- typeset [ +-HLRZfilrtux[n] ]	[ name[ =value ]  ] ...
	      Sets  attributes	and values for shell parameters.  When invoked inside a function, a new instance of the parameter name is created.
	      The parameter value and type are restored when the function completes.  The following list of attributes may be specified:
	      -H     This flag provides UNIX system to host-name file mapping on non-UNIX system machines.
	      -L     Left justify and remove leading blanks from value.  If n is non-zero it defines the width	of  the  field,  otherwise  it	is
		     determined  by the width of the value of first assignment.  When the parameter is assigned to, it is filled on the right with
		     blanks or truncated, if necessary, to fit into the field.	Leading zeros are removed if the -Z flag is also set.  The -R flag
		     is turned off.
	      -R     Right  justify  and fill with leading blanks.  If n is non-zero it defines the width of the field, otherwise it is determined
		     by the width of the value of first assignment.  The field is left filled with blanks or truncated from the end if the parame-
		     ter is reassigned.  The L flag is turned off.
	      -Z     Right justify and fill with leading zeros if the first non-blank character is a digit and the -L flag has not been set.  If n
		     is non-zero it defines the width of the field, otherwise it is determined by the width of the value of first assignment.
	      -f     The names refer to function names rather than parameter names.  No assignments can be made and the only other valid flags are
		     -t,  -u  and  -x.	 The  flag -t turns on execution tracing for this function.  The flag -u causes this function to be marked
		     undefined.  The FPATH variable will be searched to find the function definition when the function is referenced.  The flag -x
		     allows the function definition to remain in effect across shell procedures invoked by name.
	      -i     Parameter	is  an	integer.  This makes arithmetic faster.  If n is non-zero it defines the output arithmetic base, otherwise
		     the first assignment determines the output base.
	      -l     All upper-case characters converted to lower-case.  The upper-case flag, -u is turned off.
	      -r     The given names are marked readonly and these names cannot be changed by subsequent assignment.
	      -t     Tags the named parameters.  Tags are user definable and have no special meaning to the shell.
	      -u     All lower-case characters are converted to upper-case characters.	The lower-case flag, -l is turned off.
	      -x     The given names are marked for automatic export to the environment of subsequently-executed commands.

	      Using + rather than - causes these flags to be turned off.  If no name arguments are given but flags are specified, a list of  names
	      (and  optionally	the values) of the parameters which have these flags set is printed.  (Using + rather than - keeps the values from
	      being printed.)  If no names and flags are given, the names and attributes of all parameters are printed.

       ulimit [ -HSacdfmnpstvw ] [ limit ]
	      Set or display a resource limit.	The available resources limits listed below.  Many systems to not contain one  or  more  of  these
	      limits.	The  limit for a specified resource is set when limit is specified.  The value of limit can be a number in the unit speci-
	      fied below with each resource, or the value unlimited.  The H and S flags specify whether the hard limit or the soft limit  for  the
	      given  resource is set.  A hard limit cannot be increased once it is set.  A soft limit can be increased up to the value of the hard
	      limit.  If neither the H or S options is specified, the limit applies to both.  The current resource limit is printed when limit	is
	      omitted.	 In  this  case the soft limit is printed unless H is specified.  When more that one resource is specified, then the limit
	      name and unit is printed before the value.
	      -a     Lists all of the current resource limits.
	      -c     The number of 512-byte blocks on the size of core dumps.
	      -d     The number of K-bytes on the size of the data area.
	      -f     The number of 512-byte blocks on files written by child processes (files of any size may be read).
	      -m     The number of K-bytes on the size of physical memory.
	      -n     The number of file descriptors.
	      -p     The number of 512-byte blocks for pipe buffering.
	      -s     The number of K-bytes on the size of the stack area.
	      -t     The number of seconds to be used by each process.
	      -v     The number of K-bytes for virtual memory.
	      -w     The number of K-bytes for the swap area.

	      If no option is given, -f is assumed.

       umask [ mask ]
	      The user file-creation mask is set to mask (see umask(2)).  mask can either be an octal number or a symbolic value as  described	in
	      chmod(1).   If  a symbolic value is given, the new umask value is the complement of the result of applying mask to the complement of
	      the previous umask value.  If mask is omitted, the current value of the mask is printed.

       unalias name ...
	      The parameters given by the list of names are removed from the alias list.

       unset [ -f ] name ...
	      The parameters given by the list of names are unassigned, i. e., their values and attributes are erased.	Readonly variables  cannot
	      be  unset.   If  the  flag, -f, is set, then the names refer to function names.  Unsetting ERRNO, LINENO, MAILCHECK, OPTARG, OPTIND,
	      RANDOM, SECONDS, TMOUT, and _ causes removes their special meaning even if they are subsequently assigned to.

       - wait [ job ]
	      Wait for the specified job and report its termination status.  If job is not given then all currently  active  child  processes  are
	      waited for.  The exit status from this command is that of the process waited for.  See Jobs for a description of the format of job.

       whence [ -pv ] name ...
	      For each name, indicate how it would be interpreted if used as a command name.

       The flag, -v, produces a more verbose report.

       The flag, -p, does a path search for name even if name is an alias, a function, or a reserved word.

   Invocation.
       If  the	shell is invoked by exec(2), and the first character of argument zero ($0) is -, then the shell is assumed to be a login shell and
       commands are read from /etc/profile and then from either .profile in the current directory or $HOME/.profile, if either file exists.  Next,
       commands  are  read  from  the  file  named  by performing parameter substitution on the value of the environment parameter ENV if the file
       exists.	If the -s flag is not present and arg is, then a path search is performed on the first arg to determine the name of the script	to
       execute.  The script arg must have read permission and any setuid and getgid settings will be ignored.  Commands are then read as described
       below; the following flags are interpreted by the shell when it is invoked:

       -c string If the -c flag is present then commands are read from string.
       -s	 If the -s flag is present or if no arguments remain then commands are read from the standard input.  Shell output, except for the
		 output of the Special commands listed above, is written to file descriptor 2.
       -i	 If  the  -i  flag is present or if the shell input and output are attached to a terminal (as told by ioctl(2)) then this shell is
		 interactive.  In this case TERM is ignored (so that kill 0 does not kill an interactive shell) and INTR is caught and ignored (so
		 that wait is interruptible).  In all cases, QUIT is ignored by the shell.
       -r	 If the -r flag is present the shell is a restricted shell.

       The remaining flags and arguments are described under the set command above.  The command is used to set up login names and execution envi-
       ronments whose capabilities are more controlled than those of the standard shell.  The actions of are identical to those of sh, except that
       the following are disallowed:
	      changing directory (see cd(1)),
	      setting the value of SHELL, ENV, or PATH,
	      specifying path or command names containing /,
	      redirecting output (>, >| , <> , and >>).

       The restrictions above are enforced after .profile and the ENV files are interpreted.

       When  a	command  to  be executed is found to be a shell procedure, invokes to execute it.  Thus, it is possible to provide to the end-user
       shell procedures that have access to the full power of the standard shell, while imposing a limited menu of commands; this  scheme  assumes
       that the end-user does not have write and execute permissions in the same directory.

       The  net  effect  of  these rules is that the writer of the .profile has complete control over user actions, by performing guaranteed setup
       actions and leaving the user in an appropriate directory (probably not the login directory).

       The system administrator often sets up a directory of commands (that is, /usr/rbin) that can be safely invoked by Some systems also provide
       a restricted editor red.

Exit Status
       Errors  detected  by  the shell, such as syntax errors, cause the shell to return a non-zero exit status.  Otherwise, the shell returns the
       exit status of the last command executed (see also the exit command above).  If the shell is being used non-interactively then execution of
       the  shell  file  is  abandoned.  Run time errors detected by the shell are reported by printing the command or function name and the error
       condition.  If the line number that the error occurred on is greater than one, then the line number is also printed in square brackets ([])
       after the command or function name.

Files
       /etc/passwd
       /etc/profile
       /etc/suid_profile
       $HOME/.profile
       /tmp/sh*
       /dev/null

See Also
       cat(1),	cd(1),	chmod(1),  cut(1),  echo(1),  emacs(1),  env(1),  gmacs(1), newgrp(1), stty(1), test(1), umask(1), vi(1), dup(2), exec(2),
       fork(2), ioctl(2), lseek(2), paste(1), pipe(2), signal(2), umask(2), ulimit(2), wait(2), rand(3), a.out(5), profile(5), environ(7).

       Morris I. Bolsky and David G. Korn, The KornShell Command and Programming Language, Prentice Hall, 1989.

Caveats
       If a command which is a tracked alias is executed, and then a command with the same name is installed in a directory  in  the  search  path
       before  the directory where the original command was found, the shell will continue to exec the original command.  Use the -t option of the
       alias command to correct this situation.

       Some very old shell scripts contain a ^ as a synonym for the pipe character.  |.

       Using the fc built-in command within a compound command will cause the whole command to disappear from the history file.

       The built-in command . file reads the whole file before any commands are executed.  Therefore, alias and unalias commands in the file  will
       not apply to any functions defined in the file.

       Traps  are  not processed while a job is waiting for a foreground process.  Thus, a trap on CHLD won't be executed until the foreground job
       terminates.

																	    ksh(1)
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