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Linux 2.6 - man page for read (linux section 1posix)

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

NAME
       read - read a line from standard input

SYNOPSIS
       read [-r] var...

DESCRIPTION
       The read utility shall read a single line from standard input.

       By  default,  unless  the -r option is specified, backslash ( '\' ) shall act as an escape
       character, as described in Escape Character (Backslash) . If standard input is a  terminal
       device  and  the  invoking shell is interactive, read shall prompt for a continuation line
       when:

	* The shell reads an input line ending with a backslash, unless the -r option  is  speci-
	  fied.

	* A here-document is not terminated after a <newline> is entered.

       The  line  shall  be  split  into fields as in the shell (see Field Splitting ); the first
       field shall be assigned to the first variable var, the second field to the second variable
       var,  and  so  on.   If	there are fewer var operands specified than there are fields, the
       leftover fields and their intervening separators shall be assigned to  the  last  var.  If
       there are fewer fields than vars, the remaining vars shall be set to empty strings.

       The setting of variables specified by the var operands shall affect the current shell exe-
       cution environment; see Shell Execution Environment . If it is called  in  a  subshell  or
       separate utility execution environment, such as one of the following:

	      (read foo)
	      nohup read ...
	      find . -exec read ... \;

       it shall not affect the shell variables in the caller's environment.

OPTIONS
       The  read  utility  shall  conform to the Base Definitions volume of IEEE Std 1003.1-2001,
       Section 12.2, Utility Syntax Guidelines.

       The following option is supported:

       -r     Do not treat a backslash character in any special way. Consider each  backslash  to
	      be part of the input line.

OPERANDS
       The following operand shall be supported:

       var    The name of an existing or nonexisting shell variable.

STDIN
       The standard input shall be a text file.

INPUT FILES
       None.

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

       IFS    Determine the internal field separators used to delimit fields; see Shell Variables
	      .

       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_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).

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

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

       PS2    Provide  the  prompt string that an interactive shell shall write to standard error
	      when a line ending with a backslash is read and the -r option was not specified, or
	      if a here-document is not terminated after a <newline> is entered.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       Not used.

STDERR
       The standard error shall be used for diagnostic messages and prompts for continued input.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

	0     Successful completion.

       >0     End-of-file was detected or an error occurred.

CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       The -r option is included to enable read to subsume the purpose of the line utility, which
       is not included in IEEE Std 1003.1-2001.

       The results are undefined if an end-of-file is detected following a backslash at  the  end
       of a line when -r is not specified.

EXAMPLES
       The following command:

	      while read -r xx yy
	      do
		  printf "%s %s\n" "$yy" "$xx"
	      done < input_file

       prints a file with the first field of each line moved to the end of the line.

RATIONALE
       The read utility historically has been a shell built-in. It was separated off into its own
       utility to take advantage of the richer description of functionality  introduced  by  this
       volume of IEEE Std 1003.1-2001.

       Since  read affects the current shell execution environment, it is generally provided as a
       shell regular built-in. If it is called in a subshell or separate utility execution  envi-
       ronment, such as one of the following:

	      (read foo)
	      nohup read ...
	      find . -exec read ... \;

       it does not affect the shell variables in the environment of the caller.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Shell Command Language

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					  READ(P)


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