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 (Back-
       slash) . 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 specified.

	* 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 execution environment; see Shell Execution Environ-
       ment . 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,  Internationalization  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 internationalization 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 arguments).

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diagnostic 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
" "$yy" "$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 descrip-
       tion 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 sub-
       shell or separate utility execution environment, 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 Technol-
       ogy -- 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 original Standard can be obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003								   READ(P)