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


NAME
       eval — construct command by concatenating arguments


SYNOPSIS
       eval [argument...]


DESCRIPTION
       The eval utility shall construct a command by concatenating arguments together, separating
       each with a <space> character.  The constructed command shall be read and executed by  the
       shell.


OPTIONS
       None.


OPERANDS
       See the DESCRIPTION.


STDIN
       Not used.


INPUT FILES
       None.


ENVIRONMENT VARIABLES
       None.


ASYNCHRONOUS EVENTS
       Default.


STDOUT
       Not used.


STDERR
       The standard error shall be used only for diagnostic messages.


OUTPUT FILES
       None.


EXTENDED DESCRIPTION
       None.


EXIT STATUS
       If  there  are no arguments, or only null arguments, eval shall return a zero exit status;
       otherwise, it shall return the exit status  of  the  command  defined  by  the  string  of
       concatenated  arguments  separated by <space> characters, or a non-zero exit status if the
       concatenation could not be parsed as a command and the shell is interactive (and therefore
       did not abort).


CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.


APPLICATION USAGE
       Since  eval is not required to recognize the "--" end of options delimiter, in cases where
       the argument(s) to eval might begin with '-' it is recommended that the first argument  is
       prefixed  by  a  string that will not alter the commands to be executed, such as a <space>
       character:

           eval " $commands"

       or:

           eval " $(some_command)"


EXAMPLES
       foo=10 x=foo
       y='$'$x
       echo $y
       $foo
       eval y='$'$x
       echo $y
       10


RATIONALE
       This standard allows, but does not require, eval to recognize "--".  Although  this  means
       applications  cannot  use  "--"  to  protect against options supported as an extension (or
       errors reported for unsupported options), the nature of the  eval  utility  is  such  that
       other means can be used to provide this protection (see APPLICATION USAGE above).


FUTURE DIRECTIONS
       None.


SEE ALSO
       Section 2.14, Special Built-In Utilities


COPYRIGHT
       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1-2017, Standard for Information Technology -- Portable  Operating  System  Interface
       (POSIX),  The  Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       Any  typographical  or  formatting errors that appear in this page are most likely to have
       been introduced during the conversion of the source files to man page  format.  To  report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .