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OpenSolaris 2009.06 - man page for nawk (opensolaris section 1)

nawk(1) 				  User Commands 				  nawk(1)

NAME
       nawk - pattern scanning and processing language

SYNOPSIS
       /usr/bin/nawk [-F ERE] [-v assignment] 'program' | -f progfile...
	    [argument]...

       /usr/xpg4/bin/awk [-F ERE] [-v assignment]... 'program' | -f progfile...
	    [argument]...

DESCRIPTION
       The  /usr/bin/nawk  and	/usr/xpg4/bin/awk  utilities execute programs written in the nawk
       programming language, which is specialized for textual data manipulation. A  nawk  program
       is a sequence of patterns and corresponding actions. The string specifying program must be
       enclosed in single quotes (') to protect it from interpretation by the shell. The sequence
       of  pattern - action statements can be specified in the command line as program or in one,
       or more, file(s) specified by the -fprogfile option. When input is  read  that  matches	a
       pattern, the action associated with the pattern is performed.

       Input  is  interpreted  as a sequence of records. By default, a record is a line, but this
       can be changed by using the RS built-in variable. Each record of input is matched to  each
       pattern in the program. For each pattern matched, the associated action is executed.

       The nawk utility interprets each input record as a sequence of fields where, by default, a
       field is a string of  non-blank	characters.  This  default  white-space  field	delimiter
       (blanks and/or tabs) can be changed by using the FS built-in variable or the -FERE option.
       The nawk utility denotes the first field in a record $1, the second $2, and so forth.  The
       symbol  $0 refers to the entire record; setting any other field causes the reevaluation of
       $0. Assigning to $0 resets the values of all fields and the NF built-in variable.

OPTIONS
       The following options are supported:

       -F ERE		Define the input field separator to be the  extended  regular  expression
			ERE, before any input is read (can be a character).

       -f progfile	Specifies the pathname of the file progfile containing a nawk program. If
			multiple instances of this option are specified, the concatenation of the
			files  specified  as progfile in the order specified is the nawk program.
			The nawk program can alternatively be specified in the command line as	a
			single argument.

       -v assignment	The  assignment  argument must be in the same form as an assignment oper-
			and. The assignment is of the form var=value, where var is  the  name  of
			one  of  the  variables  described below. The specified assignment occurs
			before executing the nawk program, including the actions associated  with
			BEGIN patterns (if any). Multiple occurrences of this option can be spec-
			ified.

OPERANDS
       The following operands are supported:

       program	   If no -f option is specified, the first operand to nawk is  the  text  of  the
		   nawk  program.  The application supplies the program operand as a single argu-
		   ment to nawk. If the text does not end in a newline character, nawk interprets
		   the text as if it did.

       argument    Either of the following two types of argument can be intermixed:

		   file 	 A  pathname  of a file that contains the input to be read, which
				 is matched against the set of patterns in  the  program.  If  no
				 file  operands  are  specified,  or  if a file operand is -, the
				 standard input is used.

		   assignment	 An operand that begins with an underscore or alphabetic  charac-
				 ter  from  the portable character set, followed by a sequence of
				 underscores, digits and alphabetics from the portable	character
				 set, followed by the = character specifies a variable assignment
				 rather than a pathname. The characters before	the  =	represent
				 the  name  of	a  nawk variable. If that name is a nawk reserved
				 word, the behavior is undefined. The  characters  following  the
				 equal	sign  is interpreted as if they appeared in the nawk pro-
				 gram preceded and followed by a double-quote (") character, as a
				 STRING token , except that if the last character is an unescaped
				 backslash, it is interpreted as a literal backslash rather  than
				 as  the  first  character  of	the  sequence \.. The variable is
				 assigned the value of that STRING token. If the value is consid-
				 ered  a  numericstring,  the  variable  is  assigned its numeric
				 value. Each such variable assignment is  performed  just  before
				 the  processing  of the following file, if any. Thus, an assign-
				 ment before the first file argument is executed after the  BEGIN
				 actions  (if any), while an assignment after the last file argu-
				 ment is executed before the END actions (if any).  If there  are
				 no  file  arguments,  assignments are executed before processing
				 the standard input.

INPUT FILES
       Input files to the nawk program from any of the following sources:

	   o	  any file operands or their equivalents, achieved by modifying  the  nawk  vari-
		  ables ARGV and ARGC

	   o	  standard input in the absence of any file operands

	   o	  arguments to the getline function

       must be text files. Whether the variable RS is set to a value other than a newline charac-
       ter or not, for these files, implementations support records terminated with the specified
       separator up to {LINE_MAX} bytes and can support longer records.

       If -f progfile is specified, the files named by each of the progfile option-arguments must
       be text files containing an nawk program.

       The standard input are used only if no file operands are specified, or if a  file  operand
       is -.

EXTENDED DESCRIPTION
       A nawk program is composed of pairs of the form:

	 pattern { action }

       Either  the  pattern or the action (including the enclosing brace characters) can be omit-
       ted. Pattern-action statements are separated by a semicolon or by a newline.

       A missing pattern matches any record of input, and a missing action is  equivalent  to  an
       action that writes the matched record of input to standard output.

       Execution  of  the  nawk program starts by first executing the actions associated with all
       BEGIN patterns in the order they occur in the program. Then each file operand (or standard
       input  if  no  files  were  specified)  is processed by reading data from the file until a
       record separator is seen (a newline character by default), splitting  the  current  record
       into  fields  using the current value of FS, evaluating each pattern in the program in the
       order of occurrence, and executing the action associated with each  pattern  that  matches
       the current record. The action for a matching pattern is executed before evaluating subse-
       quent patterns. Last, the actions associated with all END  patterns  is	executed  in  the
       order they occur in the program.

   Expressions in nawk
       Expressions  describe  computations  used in patterns and actions. In the following table,
       valid expression operations are given in groups from highest precedence	first  to  lowest
       precedence  last,  with	equal-precedence  operators  grouped between horizontal lines. In
       expression evaluation, where the grammar is formally ambiguous, higher  precedence  opera-
       tors  are  evaluated before lower precedence operators.	In this table expr, expr1, expr2,
       and expr3 represent any expression,  while  lvalue  represents  any  entity  that  can  be
       assigned to (that is, on the left side of an assignment operator).

	   Syntax		   Name 	     Type of Result	Associativity
       --------------------------------------------------------------------------------
       ( expr ) 	 Grouping		    type of expr	n/a
       --------------------------------------------------------------------------------
       $expr		 Field reference	    string		n/a
       --------------------------------------------------------------------------------
       ++ lvalue	 Pre-increment		    numeric		n/a
	--lvalue	 Pre-decrement		    numeric		n/a
       lvalue ++	 Post-increment 	    numeric		n/a
       lvalue --	 Post-decrement 	    numeric		n/a
       --------------------------------------------------------------------------------
       expr ^ expr	 Exponentiation 	    numeric		right
       --------------------------------------------------------------------------------
       ! expr		 Logical not		    numeric		n/a
       + expr		 Unary plus		    numeric		n/a
       - expr		 Unary minus		    numeric		n/a
       --------------------------------------------------------------------------------
       expr * expr	 Multiplication 	    numeric		left
       expr / expr	 Division		    numeric		left
       expr % expr	 Modulus		    numeric		left
       --------------------------------------------------------------------------------
       expr + expr	 Addition		    numeric		left
       expr - expr	 Subtraction		    numeric		left
       --------------------------------------------------------------------------------
       expr expr	 String concatenation	    string		left
       --------------------------------------------------------------------------------
       expr < expr	 Less than		    numeric		none
       expr <= expr	 Less than or equal to	    numeric		none
       expr != expr	 Not equal to		    numeric		none
       expr == expr	 Equal to		    numeric		none
       expr > expr	 Greater than		    numeric		none
       expr >= expr	 Greater than or equal to   numeric		none
       --------------------------------------------------------------------------------
       expr ~ expr	 ERE match		    numeric		none
       expr !~ expr	 ERE non-match		     numeric		none
       --------------------------------------------------------------------------------

       expr in array	 Array membership	    numeric		left
       ( index ) in	 Multi-dimension array	    numeric		left
	   array	     membership
       --------------------------------------------------------------------------------
       expr && expr	 Logical AND		    numeric		left
       --------------------------------------------------------------------------------
       expr || expr	 Logical OR		    numeric		left
       --------------------------------------------------------------------------------
       expr1 ? expr2	 Conditional expression     type of selected	right
	   : expr3				       expr2 or expr3
       --------------------------------------------------------------------------------
       lvalue ^= expr	 Exponentiation 	    numeric		right
			 assignment
       lvalue %= expr	 Modulus assignment	    numeric		right
       lvalue *= expr	 Multiplication 	    numeric		right
			 assignment
       lvalue /= expr	 Division assignment	    numeric		right
       lvalue +=  expr	 Addition assignment	    numeric		right
       lvalue -= expr	 Subtraction assignment     numeric		right
       lvalue = expr	 Assignment		    type of expr	right

       Each  expression  has either a string value, a numeric value or both. Except as stated for
       specific contexts, the value of an expression is implicitly converted to the  type  needed
       for  the  context  in which it is used.	A string value is converted to a numeric value by
       the equivalent of the following calls:

	 setlocale(LC_NUMERIC, "");
	 numeric_value = atof(string_value);

       A numeric value that is exactly equal to the value of an integer is converted to a  string
       by the equivalent of a call to the sprintf function with the string %d as the fmt argument
       and the numeric value being converted as the first and  only  expr  argument.   Any  other
       numeric value is converted to a string by the equivalent of a call to the sprintf function
       with the value of the variable CONVFMT as the fmt argument and  the  numeric  value  being
       converted as the first and only expr argument.

       A string value is considered to be a numeric string in the following case:

	   1.	  Any leading and trailing blank characters is ignored.

	   2.	  If the first unignored character is a + or -, it is ignored.

	   3.	  If the remaining unignored characters would be lexically recognized as a NUMBER
		  token, the string is considered a numeric string.

       If a - character is ignored in the above steps, the numeric value of the numeric string is
       the  negation  of  the numeric value of the recognized NUMBER token. Otherwise the numeric
       value of the numeric string is the numeric value of the recognized NUMBER  token.  Whether
       or  not	a string is a numeric string is relevant only in contexts where that term is used
       in this section.

       When an expression is used in a Boolean context, if it has a numeric  value,  a	value  of
       zero is treated as false and any other value is treated as true. Otherwise, a string value
       of the null string is treated as false and any other value is treated as true.  A  Boolean
       context is one of the following:

	   o	  the first subexpression of a conditional expression.

	   o	  an expression operated on by logical NOT, logical AND, or logical OR.

	   o	  the second expression of a for statement.

	   o	  the expression of an if statement.

	   o	  the expression of the while clause in either a while or do ... while statement.

	   o	  an expression used as a pattern (as in Overall Program Structure).

       The  nawk  language  supplies  arrays that are used for storing numbers or strings. Arrays
       need not be declared. They are initially empty, and their sizes changes	dynamically.  The
       subscripts,  or	element  identifiers,  are strings, providing a type of associative array
       capability. An array name followed by a subscript within square brackets can be used as an
       lvalue  and  as an expression, as described in the grammar.  Unsubscripted array names are
       used in only the following contexts:

	   o	  a parameter in a function definition or function call.

	   o	  the NAME token following any use of the keyword in.

       A valid array index consists of one or more comma-separated expressions,  similar  to  the
       way  in	which multi-dimensional arrays are indexed in some programming languages. Because
       nawk arrays are really one-dimensional, such a comma-separated list is converted to a sin-
       gle  string by concatenating the string values of the separate expressions, each separated
       from the other by the value of the SUBSEP variable.

       Thus, the following two index operations are equivalent:

	 var[expr1, expr2, ... exprn]
	 var[expr1 SUBSEP expr2 SUBSEP ... SUBSEP exprn]

       A multi-dimensioned index used with the in operator must be put	in  parentheses.  The  in
       operator, which tests for the existence of a particular array element, does not create the
       element if it does not exist.  Any other reference to a non-existent array  element  auto-
       matically creates it.

   Variables and Special Variables
       Variables  can be used in an nawk program by referencing them. With the exception of func-
       tion parameters, they are not explicitly  declared.  Uninitialized  scalar  variables  and
       array elements have both a numeric value of zero and a string value of the empty string.

       Field  variables  are  designated by a $ followed by a number or numerical expression. The
       effect of the field number expression evaluating to anything  other  than  a  non-negative
       integer	is unspecified. Uninitialized variables or string values need not be converted to
       numeric values in this context. New field variables are created by assigning  a	value  to
       them.  References  to  non-existent  fields  (that  is, fields after $NF) produce the null
       string. However, assigning to a non-existent field (for example, $(NF+2)  =  5)	increases
       the  value  of  NF, create any intervening fields with the null string as their values and
       cause the value of $0 to be recomputed, with the fields being separated by  the	value  of
       OFS.  Each  field variable has a string value when created. If the string, with any occur-
       rence of the decimal-point character from the current locale changed to a  period  charac-
       ter,  is  considered  a numeric string (see Expressions in nawk above), the field variable
       also has the numeric value of the numeric string.

   /usr/bin/nawk, /usr/xpg4/bin/awk
       nawk sets the following special variables that are supported  by  both  /usr/bin/nawk  and
       /usr/xpg4/bin/awk:

       ARGC	   The number of elements in the ARGV array.

       ARGV	   An  array  of  command line arguments, excluding options and the program argu-
		   ment, numbered from zero to ARGC-1.

		   The arguments in ARGV can be modified or added to; ARGC can	be  altered.   As
		   each input file ends, nawk treats the next non-null element of ARGV, up to the
		   current value of ARGC-1, inclusive, as the name of the next input file.   Set-
		   ting an element of ARGV to null means that it is not treated as an input file.
		   The name - indicates the standard input. If an argument matches the format  of
		   an assignment operand, this argument is treated as an assignment rather than a
		   file argument.

       ENVIRON	   The variable ENVIRON is an array representing the value  of	the  environment.
		   The	indices  of the array are strings consisting of the names of the environ-
		   ment variables, and the value of each array element is a string consisting  of
		   the value of that variable. If the value of an environment variable is consid-
		   ered a numeric string, the array element also has its numeric value.

		   In all cases where nawk behavior is affected by environment variables (includ-
		   ing the environment of any commands that nawk executes via the system function
		   or via pipeline redirections with the print statement, the  printf  statement,
		   or  the getline function), the environment used is the environment at the time
		   nawk began executing.

       FILENAME    A pathname of the current input file. Inside a BEGIN action the value is unde-
		   fined.  Inside an END action the value is the name of the last input file pro-
		   cessed.

       FNR	   The ordinal number of the current record in the current file. Inside  a  BEGIN
		   action  the value is zero. Inside an END action the value is the number of the
		   last record processed in the last file processed.

       FS	   Input field separator regular expression; a space character by default.

       NF	   The number of fields in the current record. Inside a BEGIN action, the use  of
		   NF  is  undefined unless a getline function without a var argument is executed
		   previously. Inside an END action, NF retains the value it  had  for	the  last
		   record  read,  unless a subsequent, redirected, getline function without a var
		   argument is performed prior to entering the END action.

       NR	   The ordinal number of the current record from the start  of	input.	Inside	a
		   BEGIN  action  the value is zero. Inside an END action the value is the number
		   of the last record processed.

       OFMT	   The printf format for converting  numbers  to  strings  in  output  statements
		   "%.6g" by default. The result of the conversion is unspecified if the value of
		   OFMT is not a floating-point format specification.

       OFS	   The print statement output field separator; a space character by default.

       ORS	   The print output record separator; a newline character by default.

       LENGTH	   The length of the string matched by the match function.

       RS	   The first character of the string value of RS is the input record separator; a
		   newline  character  by  default.  If  RS contains more than one character, the
		   results are unspecified.  If  RS  is  null,	then  records  are  separated  by
		   sequences  of  one or more blank lines. Leading or trailing blank lines do not
		   produce empty records at the beginning or end of input, and the field  separa-
		   tor is always newline, no matter what the value of FS.

       RSTART	   The	starting  position of the string matched by the match function, numbering
		   from 1. This is always equivalent to the return value of the match function.

       SUBSEP	   The subscript separator string for multi-dimensional arrays. The default value
		   is \034.

   /usr/xpg4/bin/awk
       The following variable is supported for /usr/xpg4/bin/awk only:

       CONVFMT	  The  printf  format for converting numbers to strings (except for output state-
		  ments, where OFMT is used). The default is %.6g.

   Regular Expressions
       The nawk utility makes use of the extended  regular  expression	notation  (see	regex(5))
       except  that  it  allows  the  use  of C-language conventions to escape special characters
       within the EREs, namely \\, \a, \b, \f, \n, \r, \t, \v, and those specified in the follow-
       ing  table.  These escape sequences are recognized both inside and outside bracket expres-
       sions.  Note that records need not be separated by newline characters and string constants
       can  contain  newline  characters, so even the \n sequence is valid in nawk EREs.  Using a
       slash character within the regular expression requires escaping	as  shown  in  the  table
       below:

       Escape Sequence	 Description		    Meaning
       -----------------------------------------------------------------------
       \"		 Backslash quotation-mark   Quotation-mark character
       -----------------------------------------------------------------------
       \/		 Backslash slash	    Slash character
       -----------------------------------------------------------------------
       \ddd		 A   backslash	character   The character encoded by
			 followed by the  longest   the one-, two- or three-
			 sequence of one, two, or   digit   octal   integer.
			 three octal-digit  char-   Multi-byte	  characters
			 acters(01234567).   If   require  multiple,	con-
			 all of the digits are 0,   catenated	      escape
			 (that is, representation   sequences, including the
			 of the NULL  character),   leading \ for each byte.
			 the  behavior	is  unde-
			 fined.
       -----------------------------------------------------------------------
       \c		 A   backslash	character   Undefined
			 followed by any  charac-
			 ter   not  described  in
			 this  table  or  special
			 characters  (\\, \a, \b,
			 \f, \n, \r, \t, \v).

       A regular expression can be matched against a specific field or string by using one of the
       two  regular  expression  matching  operators,  ~  and !~. These operators interpret their
       right-hand operand as a regular expression and their left-hand operand as a string. If the
       regular	expression matches the string, the ~ expression evaluates to the value 1, and the
       !~ expression evaluates to the value 0. If the  regular	expression  does  not  match  the
       string,	the ~ expression evaluates to the value 0, and the !~ expression evaluates to the
       value 1. If the right-hand operand is any expression other than the lexical token ERE, the
       string value of the expression is interpreted as an extended regular expression, including
       the escape conventions described above. Notice that these same escape conventions also are
       applied	in  the determining the value of a string literal (the lexical token STRING), and
       is applied a second time when a string literal is used in this context.

       When an ERE token appears as an expression in any context other than as the right-hand  of
       the  ~  or  !~  operator or as one of the built-in function arguments described below, the
       value of the resulting expression is the equivalent of:

	 $0 ~ /ere/

       The ere argument to the gsub, match, sub functions, and the fs argument to the split func-
       tion  (see  String Functions) is interpreted as extended regular expressions. These can be
       either ERE tokens or arbitrary expressions, and are interpreted in the same manner as  the
       right-hand side of the ~ or !~ operator.

       An  extended  regular expression can be used to separate fields by using the -F ERE option
       or by assigning a string containing the	expression  to	the  built-in  variable  FS.  The
       default	value  of the FS variable is a single space character. The following describes FS
       behavior:

	   1.	  If FS is a single character:

	       o      If FS is the space character, skip leading and trailing  blank  characters;
		      fields are delimited by sets of one or more blank characters.

	       o      Otherwise,  if  FS  is  any other character c, fields are delimited by each
		      single occurrence of c.

	   2.	  Otherwise, the string value of FS is	considered  to	be  an	extended  regular
		  expression. Each occurrence of a sequence matching the extended regular expres-
		  sion delimits fields.

       Except in the gsub, match, split, and sub built-in functions, regular expression  matching
       is  based  on  input records. That is, record separator characters (the first character of
       the value of the variable RS, a newline character by default) cannot be	embedded  in  the
       expression,  and no expression matches the record separator character. If the record sepa-
       rator is not a newline character, newline characters embedded in  the  expression  can  be
       matched.  In  those four built-in functions, regular expression matching are based on text
       strings. So, any character (including the newline character and the record separator)  can
       be  embedded  in the pattern and an appropriate pattern matches any character. However, in
       all nawk regular expression matching, the use of one or more NULL characters in	the  pat-
       tern, input record or text string produces undefined results.

   Patterns
       A  pattern  is  any  valid  expression,	a range specified by two expressions separated by
       comma, or one of the two special patterns BEGIN or END.

   Special Patterns
       The nawk utility recognizes two special patterns, BEGIN and END.  Each  BEGIN  pattern  is
       matched	once  and its associated action executed before the first record of input is read
       (except possibly by use of the getline function in a prior BEGIN action) and  before  com-
       mand  line  assignment is done. Each END pattern is matched once and its associated action
       executed after the last record of input has been read. These two patterns have  associated
       actions.

       BEGIN  and  END	do  not combine with other patterns.  Multiple BEGIN and END patterns are
       allowed. The actions associated with the BEGIN patterns are executed in the  order  speci-
       fied in the program, as are the END actions. An END pattern can precede a BEGIN pattern in
       a program.

       If an nawk program consists of only actions with the pattern BEGIN, and the  BEGIN  action
       contains no getline function, nawk exits without reading its input when the last statement
       in the last BEGIN action is executed. If an nawk program consists of only actions with the
       pattern	END or only actions with the patterns BEGIN and END, the input is read before the
       statements in the END actions are executed.

   Expression Patterns
       An expression pattern is evaluated as if it were an expression in a  Boolean  context.  If
       the result is true, the pattern is considered to match, and the associated action (if any)
       is executed. If the result is false, the action is not executed.

   Pattern Ranges
       A pattern range consists of two expressions separated by a comma. In this case, the action
       is  performed  for  all	records between a match of the first expression and the following
       match of the second expression, inclusive.  At  this  point,  the  pattern  range  can  be
       repeated starting at input records subsequent to the end of the matched range.

   Actions
       An action is a sequence of statements. A statement can be one of the following:

	 if ( expression ) statement [ else statement ]
	 while ( expression ) statement
	 do statement while ( expression )
	 for ( expression ; expression ; expression ) statement
	 for ( var in array ) statement
	 delete array[subscript] #delete an array element
	 break
	 continue
	 { [ statement ] ... }
	 expression	   # commonly variable = expression
	 print [ expression-list ] [ >expression ]
	 printf format [ ,expression-list ] [ >expression ]
	 next		   # skip remaining patterns on this input line
	 exit [expr] # skip the rest of the input; exit status is expr
	 return [expr]

       Any  single  statement can be replaced by a statement list enclosed in braces.  The state-
       ments are terminated by newline characters or semicolons, and are executed sequentially in
       the order that they appear.

       The  next  statement causes all further processing of the current input record to be aban-
       doned. The behavior is undefined if a next statement appears or is invoked in a	BEGIN  or
       END action.

       The exit statement invokes all END actions in the order in which they occur in the program
       source and then terminate the program without reading further  input.  An  exit	statement
       inside  an END action terminates the program without further execution of END actions.  If
       an expression is specified in an exit statement, its numeric value is the exit  status  of
       nawk,  unless  subsequent  errors  are  encountered or a subsequent exit statement with an
       expression is executed.

   Output Statements
       Both print and printf statements write to standard output by default.  The output is writ-
       ten to the location specified by output_redirection if one is supplied, as follows:

	 > expression>> expression| expression

       In all cases, the expression is evaluated to produce a string that is used as a full path-
       name to write into (for > or >>) or as a command to be executed (for |). Using  the  first
       two  forms,  if	the file of that name is not currently open, it is opened, creating it if
       necessary and using the first form, truncating the file. The output then  is  appended  to
       the  file.   As long as the file remains open, subsequent calls in which expression evalu-
       ates to the same string value simply appends output to the file.  The  file  remains  open
       until  the  close  function, which is called with an expression that evaluates to the same
       string value.

       The third form writes output onto a stream piped to the input of a command. The stream  is
       created	if  no stream is currently open with the value of expression as its command name.
       The stream created is equivalent to one created by a call to the popen(3C)  function  with
       the value of expression as the command argument and a value of w as the mode argument.  As
       long as the stream remains open, subsequent calls in which  expression  evaluates  to  the
       same  string value writes output to the existing stream. The stream remains open until the
       close function is called with an expression that evaluates to the same string  value.   At
       that time, the stream is closed as if by a call to the pclose function.

       These  output statements take a comma-separated list of expression s referred in the gram-
       mar by the non-terminal symbols expr_list, print_expr_list  or  print_expr_list_opt.  This
       list  is  referred  to  here  as the expression list, and each member is referred to as an
       expression argument.

       The print statement writes the value of each expression argument onto the indicated output
       stream  separated by the current output field separator (see variable OFS above), and ter-
       minated by the output record separator (see variable ORS above). All expression	arguments
       is taken as strings, being converted if necessary; with the exception that the printf for-
       mat in OFMT is used instead of the value in CONVFMT. An empty expression list  stands  for
       the whole input record ($0).

       The  printf statement produces output based on a notation similar to the File Format Nota-
       tion used to describe file formats in this document Output is produced as  specified  with
       the  first expression argument as the string format and subsequent expression arguments as
       the strings arg1 to argn, inclusive, with the following exceptions:

	   1.	  The format is an actual character string rather than	a  graphical  representa-
		  tion. Therefore, it cannot contain empty character positions. The space charac-
		  ter in the format string, in any context other than  a  flag	of  a  conversion
		  specification,  is  treated as an ordinary character that is copied to the out-
		  put.

	   2.	  If the character set contains a Delta character and that character  appears  in
		  the format string, it is treated as an ordinary character that is copied to the
		  output.

	   3.	  The escape sequences	beginning  with  a  backslash  character  is  treated  as
		  sequences of ordinary characters that are copied to the output. Note that these
		  same sequences is interpreted lexically by nawk when	they  appear  in  literal
		  strings, but they is not treated specially by the printf statement.

	   4.	  A  field  width  or  precision can be specified as the * character instead of a
		  digit string. In this case the  next	argument  from	the  expression  list  is
		  fetched and its numeric value taken as the field width or precision.

	   5.	  The implementation does not precede or follow output from the d or u conversion
		  specifications with blank characters not specified by the format string.

	   6.	  The implementation does not precede output from the o conversion  specification
		  with leading zeros not specified by the format string.

	   7.	  For  the  c  conversion specification: if the argument has a numeric value, the
		  character whose encoding is that value is output.  If the value is zero  or  is
		  not  the  encoding of any character in the character set, the behavior is unde-
		  fined.  If the argument does not have a numeric value, the first  character  of
		  the  string  value is output; if the string does not contain any characters the
		  behavior is undefined.

	   8.	  For each conversion specification that consumes an argument, the  next  expres-
		  sion	argument  is evaluated. With the exception of the c conversion, the value
		  is converted to the appropriate type for the conversion specification.

	   9.	  If there are insufficient expression arguments to satisfy  all  the  conversion
		  specifications in the format string, the behavior is undefined.

	   10.	  If  any  character sequence in the format string begins with a % character, but
		  does not form a valid conversion specification, the behavior is unspecified.

       Both print and printf can output at least {LINE_MAX} bytes.

   Functions
       The nawk language has a variety of built-in functions:  arithmetic,  string,  input/output
       and general.

   Arithmetic Functions
       The arithmetic functions, except for int, are based on the ISO C standard. The behavior is
       undefined in cases where the ISO C standard specifies that an error be  returned  or  that
       the  behavior is undefined. Although the grammar permits built-in functions to appear with
       no arguments or parentheses, unless the argument or parentheses are indicated as  optional
       in the following list (by displaying them within the [ ] brackets), such use is undefined.

       atan2(y,x)	Return arctangent of y/x.

       cos(x)		Return cosine of x, where x is in radians.

       sin(x)		Return sine of x, where x is in radians.

       exp(x)		Return the exponential function of x.

       log(x)		Return the natural logarithm of x.

       sqrt(x)		Return the square root of x.

       int(x)		Truncate its argument to an integer. It is truncated toward 0 when x > 0.

       rand()		Return a random number n, such that 0 <= n < 1.

       srand([expr])	Set  the  seed	value  for rand to expr or use the time of day if expr is
			omitted. The previous seed value is returned.

   String Functions
       The string functions in the following list shall be supported. Although the  grammar  per-
       mits built-in functions to appear with no arguments or parentheses, unless the argument or
       parentheses are indicated as optional in the following list (by displaying them within the
       [ ] brackets), such use is undefined.

       gsub(ere,repl[,in])

	   Behave  like  sub  (see below), except that it replaces all occurrences of the regular
	   expression (like the ed utility global substitute) in $0 or in the in  argument,  when
	   specified.

       index(s,t)

	   Return the position, in characters, numbering from 1, in string s where string t first
	   occurs, or zero if it does not occur at all.

       length[([s])]

	   Return the length, in characters, of its argument taken as a string, or of  the  whole
	   record, $0, if there is no argument.

       match(s,ere)

	   Return  the	position, in characters, numbering from 1, in string s where the extended
	   regular expression ere occurs, or zero if it does not occur at all. RSTART is  set  to
	   the	starting  position (which is the same as the returned value), zero if no match is
	   found; RLENGTH is set to the length of the matched string, -1 if no match is found.

       split(s,a[,fs])

	   Split the string s into array elements a[1], a[2], ..., a[n], and return n. The  sepa-
	   ration  is done with the extended regular expression fs or with the field separator FS
	   if fs is not given. Each array element has a string value when created. If the  string
	   assigned to any array element, with any occurrence of the decimal-point character from
	   the current locale changed to a  period  character,	would  be  considered  a  numeric
	   string; the array element also has the numeric value of the numeric string. The effect
	   of a null string as the value of fs is unspecified.

       sprintf(fmt,expr,expr,...)

	   Format the expressions according to the printf format given	by  fmt  and  return  the
	   resulting string.

       sub(ere,repl[,in])

	   Substitute  the  string  repl  in  place of the first instance of the extended regular
	   expression ERE in string in and return the number of substitutions. An ampersand ( & )
	   appearing  in the string repl is replaced by the string from in that matches the regu-
	   lar expression. An ampersand preceded with a backslash ( \ )  is  interpreted  as  the
	   literal  ampersand  character.  An occurrence of two consecutive backslashes is inter-
	   preted as just a single literal backslash character.  Any other occurrence of a  back-
	   slash  (for	example, preceding any other character) is treated as a literal backslash
	   character. If repl is a string literal, the handling of the ampersand character occurs
	   after any lexical processing, including any lexical backslash escape sequence process-
	   ing. If in is specified and it is not an lvalue the behavior is undefined.  If  in  is
	   omitted, nawk uses the current record ($0) in its place.

       substr(s,m[,n])

	   Return  the	at  most  n-character substring of s that begins at position m, numbering
	   from 1. If n is missing, the length of the substring is limited by the length  of  the
	   string s.

       tolower(s)

	   Return  a string based on the string s. Each character in s that is an upper-case let-
	   ter specified to have a tolower mapping by the LC_CTYPE category of the current locale
	   is  replaced in the returned string by the lower-case letter specified by the mapping.
	   Other characters in s are unchanged in the returned string.

       toupper(s)

	   Return a string based on the string s. Each character in s that is a lower-case letter
	   specified  to have a toupper mapping by the LC_CTYPE category of the current locale is
	   replaced in the returned string by the upper-case letter  specified	by  the  mapping.
	   Other characters in s are unchanged in the returned string.

       All  of	the preceding functions that take ERE as a parameter expect a pattern or a string
       valued expression that is a regular expression as defined below.

   Input/Output and General Functions
       The input/output and general functions are:

       close(expression)	  Close the file or pipe opened by a print or printf statement or
				  a  call  to  getline with the same string-valued expression. If
				  the close was successful, the function returns 0; otherwise, it
				  returns non-zero.

       expression|getline[var]	  Read a record of input from a stream piped from the output of a
				  command. The stream is created if no stream is  currently  open
				  with	the  value  of expression as its command name. The stream
				  created is equivalent to one created by a  call  to  the  popen
				  function  with  the value of expression as the command argument
				  and a value of r as the mode argument. As long  as  the  stream
				  remains open, subsequent calls in which expression evaluates to
				  the same string value reads subsequent records from  the  file.
				  The stream remains open until the close function is called with
				  an expression that evaluates to the same string value. At  that
				  time,  the stream is closed as if by a call to the pclose func-
				  tion. If var is missing, $0 and NF is set.  Otherwise,  var  is
				  set.

				  The  getline	operator can form ambiguous constructs when there
				  are operators that are not in parentheses  (including  concate-
				  nate)  to the left of the | (to the beginning of the expression
				  containing getline). In  the	context  of  the  $  operator,	|
				  behaves  as  if it had a lower precedence than $. The result of
				  evaluating other operators is unspecified, and all such uses of
				  portable applications must be put in parentheses properly.

       getline			     Set $0 to the next input record from the current input file.
				     This form of getline sets the NF, NR, and FNR variables.

       getline var		     Set variable var to the next input record from  the  current
				     input  file.  This form of getline sets the FNR and NR vari-
				     ables.

       getline [var] < expression    Read the next record of input from a named file. The expres-
				     sion is evaluated to produce a string that is used as a full
				     pathname. If the file of that name is not currently open, it
				     is  opened.  As  long as the stream remains open, subsequent
				     calls in which expression evaluates to the same string value
				     reads  subsequent	records  from  the file. The file remains
				     open until the close function is called with  an  expression
				     that  evaluates to the same string value. If var is missing,
				     $0 and NF is set. Otherwise, var is set.

				     The getline operator  can	form  ambiguous  constructs  when
				     there  are  binary  operators  that  are  not in parentheses
				     (including concatenate) to the right of the < (up to the end
				     of  the  expression  containing  the getline). The result of
				     evaluating such a construct is  unspecified,  and	all  such
				     uses  of  portable  applications  must be put in parentheses
				     properly.

       system(expression)	     Execute the command given by expression in a manner  equiva-
				     lent  to  the system(3C) function and return the exit status
				     of the command.

       All forms of getline return 1 for successful input, 0 for end  of  file,  and  -1  for  an
       error.

       Where  strings  are  used as the name of a file or pipeline, the strings must be textually
       identical. The terminology ``same string value'' implies that ``equivalent strings'', even
       those that differ only by space characters, represent different files.

   User-defined Functions
       The nawk language also provides user-defined functions. Such functions can be defined as:

	 function name(args,...) { statements }

       A function can be referred to anywhere in an nawk program; in particular, its use can pre-
       cede its definition. The scope of a function is global.

       Function arguments can be either scalars or arrays; the behavior is undefined if an  array
       name  is  passed as an argument that the function uses as a scalar, or if a scalar expres-
       sion is passed as an argument that the function uses as an array. Function  arguments  are
       passed  by value if scalar and by reference if array name. Argument names are local to the
       function; all other variable names are global. The same name is not used as both an  argu-
       ment name and as the name of a function or a special nawk variable. The same name must not
       be used both as a variable name with global scope and as the name of a function. The  same
       name must not be used within the same scope both as a scalar variable and as an array.

       The  number  of parameters in the function definition need not match the number of parame-
       ters in the function call. Excess formal parameters can be used	as  local  variables.  If
       fewer  arguments  are supplied in a function call than are in the function definition, the
       extra parameters that are used in the function body as  scalars	are  initialized  with	a
       string value of the null string and a numeric value of zero, and the extra parameters that
       are used in the function body as arrays are initialized as empty arrays. If more arguments
       are supplied in a function call than are in the function definition, the behavior is unde-
       fined.

       When invoking a function, no white space can be placed between the function name  and  the
       opening	parenthesis.  Function	calls  can be nested and recursive calls can be made upon
       functions. Upon return from any nested or recursive function call, the values  of  all  of
       the  calling  function's  parameters  are unchanged, except for array parameters passed by
       reference. The return statement can be used to return  a  value.  If  a	return	statement
       appears outside of a function definition, the behavior is undefined.

       In  the	function definition, newline characters are optional before the opening brace and
       after the closing brace. Function definitions can appear anywhere in the program  where	a
       pattern-action pair is allowed.

USAGE
       The  index,  length, match, and substr functions should not be confused with similar func-
       tions in the ISO C standard; the nawk versions deal with characters, while the ISO C stan-
       dard deals with bytes.

       Because	the concatenation operation is represented by adjacent expressions rather than an
       explicit operator, it is often necessary to use parentheses to enforce the proper  evalua-
       tion precedence.

       See  largefile(5)  for  the  description  of  the behavior of nawk when encountering files
       greater than or equal to 2 Gbyte (2^31 bytes).

EXAMPLES
       The nawk program specified in the command line is most  easily  specified  within  single-
       quotes  (for example, 'program') for applications using sh, because nawk programs commonly
       contain characters that are special to the shell, including double-quotes.  In  the  cases
       where  a  nawk  program contains single-quote characters, it is usually easiest to specify
       most of the program as strings within single-quotes concatenated by the shell with  quoted
       single-quote characters. For example:

	 nawk '/'\''/ { print "quote:", $0 }'

       prints  all  lines  from  the standard input containing a single-quote character, prefixed
       with quote:.

       The following are examples of simple nawk programs:

       Example 1 Write to the standard output all input lines for which field 3 is  greater  than
       5:

	 $3 > 5

       Example 2 Write every tenth line:

	 (NR % 10) == 0

       Example 3 Write any line with a substring matching the regular expression:

	 /(G|D)(2[0-9][[:alpha:]]*)/

       Example	4  Print any line with a substring containing a G or D, followed by a sequence of
       digits and characters:

       This example uses character classes digit and alpha to  match  language-independent  digit
       and alphabetic characters, respectively.

	 /(G|D)([[:digit:][:alpha:]]*)/

       Example	5 Write any line in which the second field matches the regular expression and the
       fourth field does not:

	 $2 ~ /xyz/ && $4 !~ /xyz/

       Example 6 Write any line in which the second field contains a backslash:

	 $2 ~ /\\/

       Example 7 Write any line in  which  the	second	field  contains  a  backslash  (alternate
       method):

       Notice  that  backslash	escapes  are interpreted twice, once in lexical processing of the
       string and once in processing the regular expression.

	 $2 ~ "\\\\"

       Example 8 Write the second to the last and the last field in  each  line,  separating  the
       fields by a colon:

	 {OFS=":";print $(NF-1), $NF}

       Example 9 Write the line number and number of fields in each line:

       The  three  strings  representing  the line number, the colon and the number of fields are
       concatenated and that string is written to standard output.

	 {print NR ":" NF}

       Example 10 Write lines longer than 72 characters:

	 {length($0) > 72}

       Example 11 Write first two fields in opposite order separated by the OFS:

	 { print $2, $1 }

       Example 12 Same, with input fields separated by comma or  space	and  tab  characters,  or
       both:

	 BEGIN { FS = ",[\t]*|[\t]+" }
	       { print $2, $1 }

       Example 13 Add up first column, print sum and average:

	 {s += $1 }
	 END {print "sum is ", s, " average is", s/NR}

       Example 14 Write fields in reverse order, one per line (many lines out for each line in):

	 { for (i = NF; i > 0; --i) print $i }

       Example 15 Write all lines between occurrences of the strings "start" and "stop":

	 /start/, /stop/

       Example 16 Write all lines whose first field is different from the previous one:

	 $1 != prev { print; prev = $1 }

       Example 17 Simulate the echo command:

	 BEGIN	{
		for (i = 1; i < ARGC; ++i)
		      printf "%s%s", ARGV[i], i==ARGC-1?"\n":""
		}

       Example	18  Write  the	path prefixes contained in the PATH environment variable, one per
       line:

	 BEGIN	{
		n = split (ENVIRON["PATH"], path, ":")
		for (i = 1; i <= n; ++i)
		       print path[i]
		}

       Example 19 Print the file "input", filling in page numbers starting at 5:

       If there is a file named input containing page headers of the form

	 Page#

       and a file named program that contains

	 /Page/{ $2 = n++; }
	 { print }

       then the command line

	 nawk -f program n=5 input

       prints the file input, filling in page numbers starting at 5.

ENVIRONMENT VARIABLES
       See environ(5) for descriptions of the following environment variables that affect  execu-
       tion: LC_COLLATE, LC_CTYPE, LC_MESSAGES, and NLSPATH.

       LC_NUMERIC    Determine the radix character used when interpreting numeric input, perform-
		     ing conversions between numeric and string  values  and  formatting  numeric
		     output.  Regardless of locale, the period character (the decimal-point char-
		     acter of the POSIX locale) is the decimal-point character recognized in pro-
		     cessing awk programs (including assignments in command-line arguments).

EXIT STATUS
       The following exit values are returned:

       0     All input files were processed successfully.

       >0    An error occurred.

       The exit status can be altered within the program by using an exit expression.

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

   /usr/bin/nawk
       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

   /usr/xpg4/bin/awk
       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWxcu4			   |
       +-----------------------------+-----------------------------+

SEE ALSO
       awk(1),	ed(1),	egrep(1),  grep(1),  lex(1),  sed(1),  popen(3C), printf(3C), system(3C),
       attributes(5), environ(5), largefile(5), regex(5), XPG4(5)

       Aho, A. V., B. W. Kernighan, and P. J. Weinberger, The AWK Programming Language,  Addison-
       Wesley, 1988.

DIAGNOSTICS
       If  any	file  operand  is  specified and the named file cannot be accessed, nawk writes a
       diagnostic message to standard error and terminate without any further action.

       If the program specified by either the program operand or a  progfile  operand  is  not	a
       valid nawk program (as specified in EXTENDED DESCRIPTION), the behavior is undefined.

NOTES
       Input white space is not preserved on output if fields are involved.

       There  are  no explicit conversions between numbers and strings. To force an expression to
       be treated as a number add 0 to it; to force it to be treated as a string concatenate  the
       null string ("") to it.

SunOS 5.11				   24 May 2006					  nawk(1)


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