READ(1P)						     POSIX Programmer's Manual							  READ(1P)

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

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(1P)