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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, 2013 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers,  Inc
       and  The  Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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 .