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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 dif-
       fer (consult the corresponding 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 (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 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 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, Internationalization Variables for  the  prece-
              dence 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  exam-
              ple, 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 writ-
              ten 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 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, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions 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 Stan-
       dard, 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)