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SH(P)				    POSIX Programmer's Manual				    SH(P)

NAME
       sh - shell, the standard command language interpreter

SYNOPSIS
       sh [-abCefhimnuvx][-o option][+abCefhimnuvx][+o option]
	       [command_file [argument...]]

       sh -c[-abCefhimnuvx][-o option][+abCefhimnuvx][+o option]command_string
	       [command_name [argument...]]

       sh -s[-abCefhimnuvx][-o option][+abCefhimnuvx][+o option][argument]

DESCRIPTION
       The  sh	utility is a command language interpreter that shall execute commands read from a
       command line string, the standard input, or a specified file. The application shall ensure
       that  the commands to be executed are expressed in the language described in Shell Command
       Language .

       Pathname expansion shall not fail due to the size of a file.

       Shell input and output redirections have an implementation-defined offset maximum that  is
       established in the open file description.

OPTIONS
       The  sh utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Sec-
       tion 12.2, Utility Syntax Guidelines, with an extension for support of a leading plus sign
       ( '+' ) as noted below.

       The -a, -b, -C, -e, -f, -m, -n, -o option, -u, -v, and -x options are described as part of
       the set utility in Special Built-In Utilities . The option letters derived  from  the  set
       special	built-in  shall  also  be  accepted with a leading plus sign ( '+' ) instead of a
       leading hyphen (meaning the reverse case of the option as  described  in  this  volume  of
       IEEE Std 1003.1-2001).

       The following additional options shall be supported:

       -c     Read commands from the command_string operand. Set the value of special parameter 0
	      (see Special Parameters ) from the value of the command_name operand and the  posi-
	      tional parameters ($1, $2, and so on) in sequence from the remaining argument oper-
	      ands. No commands shall be read from the standard input.

       -i     Specify that the shell is interactive; see below. An implementation may treat spec-
	      ifying  the  -i  option as an error if the real user ID of the calling process does
	      not equal the effective user ID or if the real group ID does not equal  the  effec-
	      tive group ID.

       -s     Read commands from the standard input.

       If  there  are  no  operands  and  the  -c option is not specified, the -s option shall be
       assumed.

       If the -i option is present, or if there are no operands and the  shell's  standard  input
       and standard error are attached to a terminal, the shell is considered to be interactive.

OPERANDS
       The following operands shall be supported:

       -      A  single  hyphen  shall be treated as the first operand and then ignored.  If both
	      '-' and "--" are given as arguments,  or	if  other  operands  precede  the  single
	      hyphen, the results are undefined.

       argument
	      The positional parameters ($1, $2, and so on) shall be set to arguments, if any.

       command_file
	      The  pathname  of  a file containing commands. If the pathname contains one or more
	      slash characters, the implementation attempts to read that file; the file need  not
	      be executable. If the pathname does not contain a slash character:

	       * The  implementation  shall  attempt  to  read that file from the current working
		 directory; the file need not be executable.

	       * If the file is not in the current working directory, the implementation may per-
		 form  a  search for an executable file using the value of PATH , as described in
		 Command Search and Execution .

       Special parameter 0 (see Special Parameters ) shall be set to the value	of  command_file.
       If  sh  is called using a synopsis form that omits command_file, special parameter 0 shall
       be set to the value of the first argument passed to  sh	from  its  parent  (for  example,
       argv[0] for a C program), which is normally a pathname used to execute the sh utility.

       command_name

	      A  string  assigned  to  special	parameter  0  when executing the commands in com-
	      mand_string. If command_name is not specified, special parameter 0 shall be set  to
	      the  value of the first argument passed to sh from its parent (for example, argv[0]
	      for a C program), which is normally a pathname used to execute the sh utility.

       command_string

	      A string that shall be interpreted by the shell as one or more commands, as if  the
	      string  were the argument to the system() function defined in the System Interfaces
	      volume of IEEE Std 1003.1-2001.  If the command_string operand is an empty  string,
	      sh shall exit with a zero exit status.

STDIN
       The standard input shall be used only if one of the following is true:

	* The -s option is specified.

	* The -c option is not specified and no operands are specified.

	* The  script  executes one or more commands that require input from standard input (such
	  as a read command that does not redirect its input).

       See the INPUT FILES section.

       When the shell is using standard input and it invokes a command that  also  uses  standard
       input,  the  shell shall ensure that the standard input file pointer points directly after
       the command it has read when the command begins execution. It shall not read ahead in such
       a  manner  that	any characters intended to be read by the invoked command are consumed by
       the shell (whether interpreted by the shell or not) or that characters that are	not  read
       by the invoked command are not seen by the shell. When the command expecting to read stan-
       dard input is started asynchronously by an interactive shell, it  is  unspecified  whether
       characters are read by the command or interpreted by the shell.

       If the standard input to sh is a FIFO or terminal device and is set to non-blocking reads,
       then sh shall enable blocking reads on standard input. This shall remain  in  effect  when
       the command completes.

INPUT FILES
       The  input  file shall be a text file, except that line lengths shall be unlimited. If the
       input file is empty or consists solely of blank lines or comments, or both, sh shall  exit
       with a zero exit status.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of sh:

       ENV    This  variable,  when  and only when an interactive shell is invoked, shall be sub-
	      jected to parameter expansion (see Parameter Expansion )	by  the  shell,  and  the
	      resulting  value shall be used as a pathname of a file containing shell commands to
	      execute in the current environment.  The	file  need  not  be  executable.  If  the
	      expanded	value  of  ENV	is not an absolute pathname, the results are unspecified.
	      ENV shall be ignored if the real and effective user IDs or real and effective group
	      IDs of the process are different.

       FCEDIT This  variable,  when  expanded by the shell, shall determine the default value for
	      the -e editor option's editor option-argument. If FCEDIT is null or unset, ed shall
	      be used as the editor. This volume of IEEE Std 1003.1-2001 specifies the effects of
	      this variable only for systems supporting the User Portability Utilities option.

       HISTFILE
	      Determine a pathname naming a command history file. If the HISTFILE variable is not
	      set,  the shell may attempt to access or create a file .sh_history in the directory
	      referred to by the HOME environment variable. If the shell cannot obtain both  read
	      and write access to, or create, the history file, it shall use an unspecified mech-
	      anism that allows the history to operate properly. (References to history "file" in
	      this section shall be understood to mean this unspecified mechanism in such cases.)
	      An implementation may choose to access this variable  only  when	initializing  the
	      history  file;  this  initialization  shall  occur  when	fc or sh first attempt to
	      retrieve entries from, or add entries to, the  file,  as	the  result  of  commands
	      issued  by  the user, the file named by the ENV variable, or implementation-defined
	      system start-up files. Implementations may choose to disable the history list mech-
	      anism  for users with appropriate privileges who do not set HISTFILE ; the specific
	      circumstances under which this occurs are implementation-defined. If more than  one
	      instance of the shell is using the same history file, it is unspecified how updates
	      to the history file from those shells interact. As entries  are  deleted	from  the
	      history  file,  they shall be deleted oldest first.  It is unspecified when history
	      file entries  are  physically  removed  from  the  history  file.  This  volume  of
	      IEEE Std 1003.1-2001  specifies  the effects of this variable only for systems sup-
	      porting the User Portability Utilities option.

       HISTSIZE
	      Determine a decimal number representing the limit to the number  of  previous  com-
	      mands  that  are	accessible.  If  this  variable  is unset, an unspecified default
	      greater than or equal to 128 shall be used. The maximum number of commands  in  the
	      history  list  is  unspecified,  but  shall  be at least 128. An implementation may
	      choose to access	this  variable	only  when  initializing  the  history	file,  as
	      described  under	HISTFILE  .  Therefore, it is unspecified whether changes made to
	      HISTSIZE after the history file has been initialized are effective.

       HOME   Determine the pathname of the user's home directory. The contents of HOME are  used
	      in   tilde   expansion   as   described	in  Tilde  Expansion  .  This  volume  of
	      IEEE Std 1003.1-2001 specifies the effects of this variable only for  systems  sup-
	      porting the User Portability Utilities option.

       IFS    (Input  Field  Separators.)  A string treated as a list of characters that shall be
	      used for field splitting and to split lines into words with the read  command.  See
	      Field  Splitting . If IFS is not set, the shell shall behave as if the value of IFS
	      were <space>, <tab>, and <newline>. Implementations may ignore the value of IFS  in
	      the environment at the time sh is invoked, treating IFS as if it were not set.

       LANG   Provide  a  default  value for the internationalization variables that are unset or
	      null. (See the Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Inter-
	      nationalization Variables for the precedence of internationalization variables used
	      to determine the values of locale categories.)

       LC_ALL If set to a non-empty string value, override the values of all the  other  interna-
	      tionalization variables.

       LC_COLLATE

	      Determine the behavior of range expressions, equivalence classes, and multi-charac-
	      ter collating elements within pattern matching.

       LC_CTYPE
	      Determine the locale for the interpretation of sequences of bytes of text  data  as
	      characters  (for	example, single-byte as opposed to multi-byte characters in argu-
	      ments and input files), which characters are defined as  letters	(character  class
	      alpha), and the behavior of character classes within pattern matching.

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic messages written to standard error.

       MAIL   Determine a pathname of the user's mailbox file for purposes of incoming mail noti-
	      fication.  If  this  variable  is  set, the shell shall inform the user if the file
	      named by the variable is created or if its modification time has changed. Informing
	      the  user  shall be accomplished by writing a string of unspecified format to stan-
	      dard error prior to the writing of the next primary prompt string. Such check shall
	      be  performed  only  after  the completion of the interval defined by the MAILCHECK
	      variable after the last such check. The user shall be informed only if MAIL is  set
	      and  MAILPATH is not set. This volume of IEEE Std 1003.1-2001 specifies the effects
	      of this variable only for systems supporting the User Portability Utilities option.

       MAILCHECK

	      Establish a decimal integer value that specifies how often (in seconds)  the  shell
	      shall  check for the arrival of mail in the files specified by the MAILPATH or MAIL
	      variables. The default value shall be 600 seconds. If set to zero, the shell  shall
	      check before issuing each primary prompt. This volume of IEEE Std 1003.1-2001 spec-
	      ifies the effects of this variable only for systems supporting the User Portability
	      Utilities option.

       MAILPATH
	      Provide  a  list	of  pathnames and optional messages separated by colons.  If this
	      variable is set, the shell shall inform the user if any of the files named  by  the
	      variable are created or if any of their modification times change. (See the preced-
	      ing entry for MAIL for descriptions of mail arrival and user informing.) Each path-
	      name  can  be  followed  by  '%'	and a string that shall be subjected to parameter
	      expansion and written to standard error when the modification time  changes.  If	a
	      '%'  character in the pathname is preceded by a backslash, it shall be treated as a
	      literal '%' in the pathname. The default message is unspecified.

       The MAILPATH environment variable takes precedence over the MAIL variable. This volume  of
       IEEE Std 1003.1-2001  specifies	the  effects of this variable only for systems supporting
       the User Portability Utilities option.

       NLSPATH
	      Determine the location of message catalogs for the processing of LC_MESSAGES .

       PATH   Establish a string formatted  as	described  in  the  Base  Definitions  volume  of
	      IEEE Std 1003.1-2001,  Chapter  8,  Environment  Variables,  used to effect command
	      interpretation; see Command Search and Execution .

       PWD    This variable shall represent an absolute pathname of the  current  working  direc-
	      tory.  Assignments  to this variable may be ignored unless the value is an absolute
	      pathname of the current working directory and there are no filename  components  of
	      dot or dot-dot.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       See the STDERR section.

STDERR
       Except as otherwise stated (by the descriptions of any invoked utilities or in interactive
       mode), standard error shall be used only for diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       See Shell Command Language . The following additional capabilities are supported  on  sys-
       tems supporting the User Portability Utilities option.

   Command History List
       When the sh utility is being used interactively, it shall maintain a list of commands pre-
       viously entered from the terminal in the file named by the HISTFILE environment	variable.
       The  type,  size,  and internal format of this file are unspecified. Multiple sh processes
       can share access to the file for a user, if file access permissions allow  this;  see  the
       description of the HISTFILE environment variable.

   Command Line Editing
       When  sh  is being used interactively from a terminal, the current command and the command
       history (see fc ) can be edited using vi-mode command line editing. This  mode  uses  com-
       mands,  described below, similar to a subset of those described in the vi utility.  Imple-
       mentations may offer other command line editing modes corresponding to other editing util-
       ities.

       The  command  set -o vi shall enable vi-mode editing and place sh into vi insert mode (see
       Command Line Editing (vi-mode) ). This command also shall disable any other  editing  mode
       that the implementation may provide. The command set +o vi disables vi-mode editing.

       Certain	block-mode  terminals  may  be unable to support shell command line editing. If a
       terminal is unable to provide either edit mode, it need not be possible to set -o vi  when
       using the shell on this terminal.

       In  the	following  sections,  the  characters erase, interrupt, kill, and end-of-file are
       those set by the stty utility.

   Command Line Editing (vi-mode)
       In vi editing mode, there shall be a distinguished line, the edit line.	All  the  editing
       operations  which  modify  a line affect the edit line. The edit line is always the newest
       line in the command history buffer.

       With vi-mode enabled, sh can be switched between insert mode and command mode.

       When in insert mode, an entered character shall be inserted into the command line,  except
       as  noted  in  vi Line Editing Insert Mode . Upon entering sh and after termination of the
       previous command, sh shall be in insert mode.

       Typing an escape character shall switch sh into command mode (see vi Line Editing  Command
       Mode  ). In command mode, an entered character shall either invoke a defined operation, be
       used as part of a multi-character operation, or be treated as an error. A  character  that
       is  not recognized as part of an editing command shall terminate any specific editing com-
       mand and shall alert the terminal. Typing the interrupt character in  command  mode  shall
       cause sh to terminate command line editing on the current command line, reissue the prompt
       on the next line of the terminal, and reset the command history (see fc ) so that the most
       recently  executed  command  is	the previous command (that is, the command that was being
       edited when it was interrupted is not reentered into the history).

       In the following sections, the phrase "move the cursor to the beginning of the word" shall
       mean "move the cursor to the first character of the current word" and the phrase "move the
       cursor to the end of the word" shall mean "move the cursor to the last  character  of  the
       current	word". The phrase "beginning of the command line" indicates the point between the
       end of the prompt string issued by the shell (or the beginning of the  terminal	line,  if
       there is no prompt string) and the first character of the command text.

   vi Line Editing Insert Mode
       While  in  insert mode, any character typed shall be inserted in the current command line,
       unless it is from the following set.

       <newline>
	      Execute the current command line. If the current command line is	not  empty,  this
	      line shall be entered into the command history (see fc ).

       erase  Delete  the  character previous to the current cursor position and move the current
	      cursor position back one character. In insert mode, characters shall be erased from
	      both the screen and the buffer when backspacing.

       interrupt
	      Terminate  command line editing with the same effects as described for interrupting
	      command mode; see Command Line Editing (vi-mode) .

       kill   Clear all the characters from the input line.

       <control>-V
	      Insert the next character input, even if	the  character	is  otherwise  a  special
	      insert mode character.

       <control>-W
	      Delete  the  characters  from  the  one  preceding the cursor to the preceding word
	      boundary. The word boundary in this case is the closer to the cursor of either  the
	      beginning of the line or a character that is in neither the blank nor punct charac-
	      ter classification of the current locale.

       end-of-file
	      Interpreted as the end of input in sh. This interpretation shall occur only at  the
	      beginning  of  an input line. If end-of-file is entered other than at the beginning
	      of the line, the results are unspecified.

       <ESC>  Place sh into command mode.

   vi Line Editing Command Mode
       In command mode for the command line editing feature, decimal digits not beginning with	0
       that  precede a command letter shall be remembered. Some commands use these decimal digits
       as a count number that affects the operation.

       The term motion command represents one of the commands:

	      <space>  0  b  F	l  W  ^  $  ;  E  f  T	w  |  ,  B  e  h  t

       If the current line is not the edit line, any command that modifies the current line shall
       cause  the  content  of	the current line to replace the content of the edit line, and the
       current line shall become the edit line. This replacement cannot be undone (see the u  and
       U  commands  below).  The modification requested shall then be performed to the edit line.
       When the current line is the edit line, the modification shall be  done	directly  to  the
       edit line.

       Any command that is preceded by count shall take a count (the numeric value of any preced-
       ing decimal digits). Unless otherwise noted, this count shall cause the	specified  opera-
       tion to repeat by the number of times specified by the count. Also unless otherwise noted,
       a count that is out of range is considered an error condition and shall alert  the  termi-
       nal, but neither the cursor position, nor the command line, shall change.

       The  terms word and bigword are used as defined in the vi description.  The term save buf-
       fer corresponds to the term unnamed buffer in vi.

       The following commands shall be recognized in command mode:

       <newline>
	      Execute the current command line. If the current command line is	not  empty,  this
	      line shall be entered into the command history (see fc ).

       <control>-L
	      Redraw  the  current  command line. Position the cursor at the same location on the
	      redrawn line.

       #      Insert the character '#' at the beginning of the current command line and treat the
	      resulting edit line as a comment.  This line shall be entered into the command his-
	      tory; see fc .

       =      Display the possible shell word expansions (see Word Expansions ) of the bigword at
	      the current command line position.

       Note:
	      This  does not modify the content of the current line, and therefore does not cause
	      the current line to become the edit line.

       These expansions shall be displayed on subsequent terminal lines.  If the bigword contains
       none  of  the  characters  '?'  ,  '*'  , or '[' , an asterisk ( '*' ) shall be implicitly
       assumed at the end. If any directories are matched, these  expansions  shall  have  a  '/'
       character  appended.   After  the expansion, the line shall be redrawn, the cursor reposi-
       tioned at the current cursor position, and sh shall be placed in command mode.

       \      Perform pathname expansion (see Pathname Expansion ) on the current bigword, up  to
	      the  largest  set  of characters that can be matched uniquely.  If the bigword con-
	      tains none of the characters '?' , '*' , or '[' , an asterisk  (	'*'  )	shall  be
	      implicitly assumed at the end. This maximal expansion then shall replace the origi-
	      nal bigword in the command line, and the cursor shall be placed after  this  expan-
	      sion.  If  the resulting bigword completely and uniquely matches a directory, a '/'
	      character shall be inserted directly after the bigword. If some other file is  com-
	      pletely  matched,  a single <space> shall be inserted after the bigword. After this
	      operation, sh shall be placed in insert mode.

       *      Perform pathname expansion on the current bigword and insert  all  expansions  into
	      the command to replace the current bigword, with each expansion separated by a sin-
	      gle <space>. If at the end of the line, the current cursor position shall be  moved
	      to  the  first  column  position following the expansions and sh shall be placed in
	      insert mode. Otherwise, the current cursor position shall be the last column  posi-
	      tion  of	the first character after the expansions and sh shall be placed in insert
	      mode. If the current bigword contains none of the characters '?'	, '*' , or '['	,
	      before the operation, an asterisk shall be implicitly assumed at the end.

       @letter
	      Insert  the value of the alias named _letter. The symbol letter represents a single
	      alphabetic character from the portable character set; implementations  may  support
	      additional  characters as an extension. If the alias _letter contains other editing
	      commands, these commands shall be performed as part of the insertion. If	no  alias
	      _letter is enabled, this command shall have no effect.

       [count]~
	      Convert,	if  the current character is a lowercase letter, to the equivalent upper-
	      case letter and vice versa, as prescribed by the current locale. The current cursor
	      position	then  shall be advanced by one character. If the cursor was positioned on
	      the last character of the line, the case conversion shall  occur,  but  the  cursor
	      shall  not advance. If the '~' command is preceded by a count, that number of char-
	      acters shall be converted, and the cursor shall be advanced to the character  posi-
	      tion  after the last character converted. If the count is larger than the number of
	      characters after the cursor, this shall not be  considered  an  error;  the  cursor
	      shall advance to the last character on the line.

       [count].
	      Repeat  the  most  recent non-motion command, even if it was executed on an earlier
	      command line. If the previous command was preceded by a  count,  and  no	count  is
	      given on the '.'	command, the count from the previous command shall be included as
	      part of the repeated command. If the '.' command is preceded by a count, this shall
	      override any count argument to the previous command. The count specified in the '.'
	      command shall become the count for subsequent '.' commands issued without a count.

       [number]v
	      Invoke the vi editor to edit the current command line in a temporary file. When the
	      editor  exits,  the  commands in the temporary file shall be executed and placed in
	      the command history. If a number is included, it specifies the  command  number  in
	      the command history to be edited, rather than the current command line.

       [count]l   (ell)

       [count]<space>

	      Move  the current cursor position to the next character position. If the cursor was
	      positioned on the last character of the line, the terminal shall be alerted and the
	      cursor shall not be advanced.  If the count is larger than the number of characters
	      after the cursor, this shall not be considered an error; the cursor  shall  advance
	      to the last character on the line.

       [count]h
	      Move  the  current  cursor  position  to the countth (default 1) previous character
	      position. If the cursor was positioned on the first character of the line, the ter-
	      minal  shall  be	alerted and the cursor shall not be moved. If the count is larger
	      than the number of characters before the cursor, this shall not  be  considered  an
	      error; the cursor shall move to the first character on the line.

       [count]w
	      Move  to the start of the next word. If the cursor was positioned on the last char-
	      acter of the line, the terminal shall be	alerted  and  the  cursor  shall  not  be
	      advanced.  If  the  count is larger than the number of words after the cursor, this
	      shall not be considered an error; the cursor shall advance to the last character on
	      the line.

       [count]W
	      Move  to	the  start  of the next bigword. If the cursor was positioned on the last
	      character of the line, the terminal shall be alerted and the cursor  shall  not  be
	      advanced. If the count is larger than the number of bigwords after the cursor, this
	      shall not be considered an error; the cursor shall advance to the last character on
	      the line.

       [count]e
	      Move  to	the  end of the current word. If at the end of a word, move to the end of
	      the next word. If the cursor was positioned on the last character of the line,  the
	      terminal	shall  be  alerted  and the cursor shall not be advanced. If the count is
	      larger than the number of words after the cursor, this shall not be  considered  an
	      error; the cursor shall advance to the last character on the line.

       [count]E
	      Move to the end of the current bigword. If at the end of a bigword, move to the end
	      of the next bigword. If the cursor was positioned on  the  last  character  of  the
	      line,  the  terminal  shall be alerted and the cursor shall not be advanced. If the
	      count is larger than the number of bigwords after the cursor,  this  shall  not  be
	      considered an error; the cursor shall advance to the last character on the line.

       [count]b
	      Move  to	the beginning of the current word. If at the beginning of a word, move to
	      the beginning of the previous word. If the cursor was positioned on the first char-
	      acter of the line, the terminal shall be alerted and the cursor shall not be moved.
	      If the count is larger than the number of words preceding the  cursor,  this  shall
	      not  be  considered an error; the cursor shall return to the first character on the
	      line.

       [count]B
	      Move to the beginning of the current bigword. If at the  beginning  of  a  bigword,
	      move to the beginning of the previous bigword.  If the cursor was positioned on the
	      first character of the line, the terminal shall be alerted and the cursor shall not
	      be moved.  If the count is larger than the number of bigwords preceding the cursor,
	      this shall not be considered an error; the cursor shall return to the first charac-
	      ter on the line.

       ^      Move  the  current cursor position to the first character on the input line that is
	      not a <blank>.

       $      Move to the last character position on the current command line.

       0      (Zero.) Move to the first character position on the current command line.

       [count]|
	      Move to the countth character position on the current command line. If no number is
	      specified,  move	to the first position. The first character position shall be num-
	      bered 1. If the count is larger than the number of characters  on  the  line,  this
	      shall  not be considered an error; the cursor shall be placed on the last character
	      on the line.

       [count]fc
	      Move to the first occurrence of the character 'c' that  occurs  after  the  current
	      cursor  position.  If  the cursor was positioned on the last character of the line,
	      the terminal shall be alerted and the cursor shall not be advanced. If the  charac-
	      ter  'c' does not occur in the line after the current cursor position, the terminal
	      shall be alerted and the cursor shall not be moved.

       [count]Fc
	      Move to the first occurrence of the character 'c' that occurs  before  the  current
	      cursor  position.  If the cursor was positioned on the first character of the line,
	      the terminal shall be alerted and the cursor shall not be moved. If  the	character
	      'c'  does  not  occur  in the line before the current cursor position, the terminal
	      shall be alerted and the cursor shall not be moved.

       [count]tc
	      Move to the character before the first occurrence of the character 'c' that  occurs
	      after  the current cursor position.  If the cursor was positioned on the last char-
	      acter of the line, the terminal shall be	alerted  and  the  cursor  shall  not  be
	      advanced.  If the character 'c' does not occur in the line after the current cursor
	      position, the terminal shall be alerted and the cursor shall not be moved.

       [count]Tc
	      Move to the character after the first occurrence of the character 'c'  that  occurs
	      before  the  current  cursor  position.	If the cursor was positioned on the first
	      character of the line, the terminal shall be alerted and the cursor  shall  not  be
	      moved.   If  the character 'c' does not occur in the line before the current cursor
	      position, the terminal shall be alerted and the cursor shall not be moved.

       [count];
	      Repeat the most recent f, F, t, or T command.  Any number argument on that previous
	      command shall be ignored. Errors are those described for the repeated command.

       [count],
	      Repeat the most recent f, F, t, or T command.  Any number argument on that previous
	      command shall be ignored. However, reverse the direction of that command.

       a      Enter insert mode after the current cursor position. Characters  that  are  entered
	      shall be inserted before the next character.

       A      Enter insert mode after the end of the current command line.

       i      Enter insert mode at the current cursor position. Characters that are entered shall
	      be inserted before the current character.

       I      Enter insert mode at the beginning of the current command line.

       R      Enter insert mode, replacing characters from the command line beginning at the cur-
	      rent cursor position.

       [count]cmotion

	      Delete  the  characters between the current cursor position and the cursor position
	      that would result from the specified motion command. Then enter insert mode  before
	      the  first  character  following	any deleted characters. If count is specified, it
	      shall be applied to the motion command. A count shall be ignored for the	following
	      motion commands:

	      0    ^	$    c

       If the motion command is the character 'c' , the current command line shall be cleared and
       insert mode shall be entered. If the motion command would move the current cursor position
       toward  the beginning of the command line, the character under the current cursor position
       shall not be deleted. If the motion command would move the current cursor position  toward
       the  end  of  the  command  line, the character under the current cursor position shall be
       deleted. If the count is larger than the number of characters between the  current  cursor
       position  and  the  end of the command line toward which the motion command would move the
       cursor, this shall not be considered an error; all of  the  remaining  characters  in  the
       aforementioned range shall be deleted and insert mode shall be entered. If the motion com-
       mand is invalid, the terminal shall be alerted, the cursor shall not be moved, and no text
       shall be deleted.

       C      Delete  from  the current character to the end of the line and enter insert mode at
	      the new end-of-line.

       S      Clear the entire edit line and enter insert mode.

       [count]rc
	      Replace the current character with the character 'c' . With a number count, replace
	      the  current  and the following count-1 characters. After this command, the current
	      cursor position shall be on the last character that was changed. If  the	count  is
	      larger than the number of characters after the cursor, this shall not be considered
	      an error; all of the remaining characters shall be changed.

       [count]_
	      Append a <space> after the current character position and then append the last big-
	      word in the previous input line after the <space>. Then enter insert mode after the
	      last character just appended. With a number count, append the  countth  bigword  in
	      the previous line.

       [count]x
	      Delete  the  character at the current cursor position and place the deleted charac-
	      ters in the save buffer. If the cursor was positioned on the last character of  the
	      line,  the character shall be deleted and the cursor position shall be moved to the
	      previous character (the new last character). If the count is larger than the number
	      of  characters  after  the  cursor,  this shall not be considered an error; all the
	      characters from the cursor to the end of the line shall be deleted.

       [count]X
	      Delete the character before the current cursor position and place the deleted char-
	      acters  in  the  save buffer. The character under the current cursor position shall
	      not change. If the cursor was positioned on the first character of  the  line,  the
	      terminal shall be alerted, and the X command shall have no effect. If the line con-
	      tained a single character, the X command shall have no effect.  If  the  line  con-
	      tained  no  characters,  the  terminal shall be alerted and the cursor shall not be
	      moved. If the count is larger than the number of characters before the cursor, this
	      shall  not be considered an error; all the characters from before the cursor to the
	      beginning of the line shall be deleted.

       [count]dmotion

	      Delete the characters between the current cursor position and the  character  posi-
	      tion  that  would result from the motion command. A number count repeats the motion
	      command count times. If the motion command would move toward the beginning  of  the
	      command line, the character under the current cursor position shall not be deleted.
	      If the motion command is d, the entire current command line shall  be  cleared.  If
	      the  count is larger than the number of characters between the current cursor posi-
	      tion and the end of the command line toward which the motion command would move the
	      cursor,  this  shall not be considered an error; all of the remaining characters in
	      the aforementioned range shall be deleted. The deleted characters shall  be  placed
	      in the save buffer.

       D      Delete  all characters from the current cursor position to the end of the line. The
	      deleted characters shall be placed in the save buffer.

       [count]ymotion

	      Yank (that is, copy) the characters from the current cursor position to  the  posi-
	      tion  resulting  from the motion command into the save buffer. A number count shall
	      be applied to the motion command.  If the motion	command  would	move  toward  the
	      beginning  of  the  command  line,  the character under the current cursor position
	      shall not be included in the set of yanked characters. If the motion command is  y,
	      the  entire  current command line shall be yanked into the save buffer. The current
	      cursor position shall be unchanged. If the count is larger than the number of char-
	      acters  between  the current cursor position and the end of the command line toward
	      which the motion command would move the cursor, this shall  not  be  considered  an
	      error; all of the remaining characters in the aforementioned range shall be yanked.

       Y      Yank  the  characters  from the current cursor position to the end of the line into
	      the save buffer. The current character position shall be unchanged.

       [count]p
	      Put a copy of the current contents of the save  buffer  after  the  current  cursor
	      position.  The  current cursor position shall be advanced to the last character put
	      from the save buffer. A count shall indicate how many copies  of	the  save  buffer
	      shall be put.

       [count]P
	      Put  a  copy  of	the current contents of the save buffer before the current cursor
	      position. The current cursor position shall be moved to the last character put from
	      the save buffer. A count shall indicate how many copies of the save buffer shall be
	      put.

       u      Undo the last command that changed the edit line. This operation shall not undo the
	      copy of any command line to the edit line.

       U      Undo  all  changes made to the edit line. This operation shall not undo the copy of
	      any command line to the edit line.

       [count]k

       [count]-
	      Set the current command line to be the countth previous command line in  the  shell
	      command history. If count is not specified, it shall default to 1. The cursor shall
	      be positioned on the first character of the new command. If a k or - command  would
	      retreat  past  the maximum number of commands in effect for this shell (affected by
	      the HISTSIZE environment variable), the terminal shall be alerted, and the  command
	      shall have no effect.

       [count]j

       [count]+
	      Set  the current command line to be the countth next command line in the shell com-
	      mand history. If count is not specified, it shall default to 1. The cursor shall be
	      positioned  on the first character of the new command. If a j or + command advances
	      past the edit line, the current command line shall be restored to the edit line and
	      the terminal shall be alerted.

       [number]G
	      Set the current command line to be the oldest command line stored in the shell com-
	      mand history. With a number number, set the current command line to be the  command
	      line  number  in	the  history. If command line number does not exist, the terminal
	      shall be alerted and the command line shall not be changed.

       /pattern<newline>

	      Move backwards through the command history, searching for  the  specified  pattern,
	      beginning  with  the previous command line. Patterns use the pattern matching nota-
	      tion described in Pattern Matching Notation , except that the '^'  character  shall
	      have  special  meaning  when  it appears as the first character of pattern. In this
	      case, the '^' is discarded and the characters after the '^' shall be  matched  only
	      at  the  beginning  of  a line. Commands in the command history shall be treated as
	      strings, not as filenames.  If the pattern is not found, the current  command  line
	      shall  be unchanged and the terminal is alerted. If it is found in a previous line,
	      the current command line shall be set to that line and the cursor shall be  set  to
	      the first character of the new command line.

       If pattern is empty, the last non-empty pattern provided to / or ? shall be used. If there
       is no previous non-empty pattern, the terminal shall be alerted and  the  current  command
       line shall remain unchanged.

       ?pattern<newline>

	      Move  forwards  through  the  command history, searching for the specified pattern,
	      beginning with the next command line. Patterns use the  pattern  matching  notation
	      described  in  Pattern Matching Notation , except that the '^' character shall have
	      special meaning when it appears as the first character of pattern.  In  this  case,
	      the  '^' is discarded and the characters after the '^' shall be matched only at the
	      beginning of a line. Commands in the command history shall be treated  as  strings,
	      not  as  filenames.  If the pattern is not found, the current command line shall be
	      unchanged and the terminal alerted. If it is found in a following line, the current
	      command  line  shall  be	set  to that line and the cursor shall be set to the fist
	      character of the new command line.

       If pattern is empty, the last non-empty pattern provided to / or ? shall be used. If there
       is  no  previous  non-empty pattern, the terminal shall be alerted and the current command
       line shall remain unchanged.

       n      Repeat the most recent / or ? command. If there is no previous / or ?, the terminal
	      shall be alerted and the current command line shall remain unchanged.

       N      Repeat  the  most  recent / or ? command, reversing the direction of the search. If
	      there is no previous / or ?, the terminal shall be alerted and the current  command
	      line shall remain unchanged.

EXIT STATUS
       The following exit values shall be returned:

	   0  The script to be executed consisted solely of zero or more blank lines or comments,
	      or both.

       1-125  A non-interactive shell detected a  syntax,  redirection,  or  variable  assignment
	      error.

	 127  A specified command_file could not be found by a non-interactive shell.

       Otherwise,  the	shell  shall  return  the  exit  status of the last command it invoked or
       attempted to invoke (see also the exit utility in Special Built-In Utilities ).

CONSEQUENCES OF ERRORS
       See Consequences of Shell Errors .

       The following sections are informative.

APPLICATION USAGE
       Standard input and standard error are the files that determine whether a shell is interac-
       tive when -i is not specified.  For example:

	      sh > file

       and:

	      sh 2> file

       create interactive and non-interactive shells, respectively. Although both accept terminal
       input, the results of error conditions are different,  as  described  in  Consequences  of
       Shell Errors ; in the second example a redirection error encountered by a special built-in
       utility aborts the shell.

       A conforming application must protect its first operand, if it starts with a plus sign, by
       preceding it with the "--" argument that denotes the end of the options.

       Applications  should  note  that  the  standard	PATH to the shell cannot be assumed to be
       either /bin/sh or /usr/bin/sh, and should be  determined  by  interrogation  of	the  PATH
       returned by getconf PATH , ensuring that the returned pathname is an absolute pathname and
       not a shell built-in.

       For example, to determine the location of the standard sh utility:

	      command -v sh

       On some implementations this might return:

	      /usr/xpg4/bin/sh

       Furthermore, on systems that support executable scripts (the "#!"  construct), it is  rec-
       ommended  that  applications  using  executable	scripts  install them using getconf -v to
       determine the shell pathname and update the "#!"  script  appropriately	as  it	is  being
       installed (for example, with sed). For example:

	      #
	      # Installation time script to install correct POSIX shell pathname
	      #
	      # Get list of paths to check
	      #
	      Sifs=$IFS
	      IFS=:
	      set $(getconf PATH)
	      IFS=$Sifs
	      #
	      # Check each path for 'sh'
	      #
	      for i in $@
	      do
		  if [ -f ${i}/sh ];
		  then
		      Pshell=${i}/sh
		  fi
	      done
	      #
	      # This is the list of scripts to update. They should be of the
	      # form '${name}.source' and will be transformed to '${name}'.
	      # Each script should begin:
	      #
	      # !INSTALLSHELLPATH -p
	      #
	      scripts="a b c"
	      #
	      # Transform each script
	      #
	      for i in ${scripts}
	      do
		  sed -e "s|INSTALLSHELLPATH|${Pshell}|" < ${i}.source > ${i}
	      done

EXAMPLES
	1. Execute a shell command from a string:

	   sh -c "cat myfile"

	2. Execute a shell script from a file in the current directory:

	   sh my_shell_cmds

RATIONALE
       The sh utility and the set special built-in utility share a common set of options.

       The  KornShell ignores the contents of IFS upon entry to the script. A conforming applica-
       tion cannot rely on importing IFS . One justification for this, beyond security considera-
       tions,  is to assist possible future shell compilers. Allowing IFS to be imported from the
       environment prevents many optimizations that might otherwise  be  performed  via  dataflow
       analysis of the script itself.

       The text in the STDIN section about non-blocking reads concerns an instance of sh that has
       been invoked, probably by a C-language program, with standard input that has  been  opened
       using   the   O_NONBLOCK   flag;   see	open()	 in   the  System  Interfaces  volume  of
       IEEE Std 1003.1-2001. If the shell did not reset this flag, it would immediately terminate
       because no input data would be available yet and that would be considered the same as end-
       of-file.

       The options associated with a restricted shell (command name rsh and the -r  option)  were
       excluded  because  the  standard  developers considered that the implied level of security
       could not be achieved and they did not want to raise false expectations.

       On systems that support set-user-ID scripts, a historical trapdoor  has	been  to  link	a
       script to the name -i. When it is called by a sequence such as:

	      sh -

       or by:

	      #! usr/bin/sh -

       the  historical	systems have assumed that no option letters follow.  Thus, this volume of
       IEEE Std 1003.1-2001 allows the single hyphen to mark the end of the options, in  addition
       to the use of the regular "--" argument, because it was considered that the older practice
       was so pervasive. An alternative approach is taken by the KornShell, where real and effec-
       tive  user/group  IDs  must  match for an interactive shell; this behavior is specifically
       allowed by this volume of IEEE Std 1003.1-2001.

       Note:  There are other problems with set-user-ID scripts that the two approaches described
	      here do not resolve.

       The  initialization  process  for the history file can be dependent on the system start-up
       files, in that they may contain commands that effectively preempt the user's  settings  of
       HISTFILE and HISTSIZE . For example, function definition commands are recorded in the his-
       tory file, unless the set -o nolog option is set. If  the  system  administrator  includes
       function  definitions in some system start-up file called before the ENV file, the history
       file is initialized before the user gets a chance to  influence	its  characteristics.  In
       some  historical  shells, the history file is initialized just after the ENV file has been
       processed.  Therefore, it is implementation-defined whether changes made to HISTFILE after
       the history file has been initialized are effective.

       The  default  messages for the various MAIL -related messages are unspecified because they
       vary across implementations.  Typical messages are:

	      "you have mail\n"

       or:

	      "you have new mail\n"

       It is important that the descriptions of command line editing refer to the same	shell  as
       that in IEEE Std 1003.1-2001 so that interactive users can also be application programmers
       without having to deal with programmatic differences in their two environments. It is also
       essential  that the utility name sh be specified because this explicit utility name is too
       firmly rooted in historical practice of application programs for it to change.

       Consideration was given to mandating a diagnostic message when attempting to  set  vi-mode
       on terminals that do not support command line editing. However, it is not historical prac-
       tice for the shell to be cognizant of all terminal types and thus be able to detect  inap-
       propriate terminals in all cases.  Implementations are encouraged to supply diagnostics in
       this case whenever possible, rather than leaving the user in a state  where  editing  com-
       mands work incorrectly.

       In early proposals, the KornShell-derived emacs mode of command line editing was included,
       even though the emacs editor itself was not. The community of emacs proponents was adamant
       that the full emacs editor not be standardized because they were concerned that an attempt
       to standardize this very powerful environment would encourage  vendors  to  ship  strictly
       conforming  versions  lacking  the extensibility required by the community.  The author of
       the original emacs program also expressed his desire to	omit  the  program.  Furthermore,
       there were a number of historical systems that did not include emacs, or included it with-
       out supporting it, but there were very few that did not include and support vi. The  shell
       emacs  command  line  editing mode was finally omitted because it became apparent that the
       KornShell version and the editor being distributed with the GNU	system	had  diverged  in
       some  respects.	The author of emacs requested that the POSIX emacs mode either be deleted
       or have a significant number of unspecified  conditions.  Although  the	KornShell  author
       agreed  to  consider  changes  to  bring the shell into alignment, the standard developers
       decided to defer specification at that time. At the time, it was assumed that  convergence
       on an acceptable definition would occur for a subsequent draft, but that has not happened,
       and there appears to be no impetus to do so. In any  case,  implementations  are  free  to
       offer  additional  command  line  editing modes based on the exact models of editors their
       users are most comfortable with.

       Early proposals had the following list entry in vi Line Editing Insert Mode :

       \      If followed by the erase or kill character, that character shall be  inserted  into
	      the  input  line.  Otherwise, the backslash itself shall be inserted into the input
	      line.

       However, this is not actually a feature of sh command line editing insert mode, but one of
       some historical terminal line drivers. Some conforming implementations continue to do this
       when the stty iexten flag is set.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Shell Command Language , cd , echo , exit() , fc , pwd , read() , set  ,  stty  ,  test	,
       umask()	, vi , the System Interfaces volume of IEEE Std 1003.1-2001, dup(), exec, exit(),
       fork(), open(), pipe(), signal(), system(), ulimit(), umask(), wait()

COPYRIGHT
       Portions of this text are reprinted and	reproduced  in	electronic  form  from	IEEE  Std
       1003.1,	2003  Edition,	Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003  by
       the  Institute  of  Electrical  and  Electronics Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE  and  The  Open  Group
       Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					    SH(P)
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