{"id":5989,"date":"2022-12-20T18:57:48","date_gmt":"2022-12-20T21:57:48","guid":{"rendered":"http:\/\/lode.uno\/linux-man\/index.php\/2022\/12\/20\/eval-man1p\/"},"modified":"2022-12-20T18:57:48","modified_gmt":"2022-12-20T21:57:48","slug":"eval-man1p","status":"publish","type":"post","link":"https:\/\/lode.uno\/linux-man\/2022\/12\/20\/eval-man1p\/","title":{"rendered":"EVAL (man1p)"},"content":{"rendered":"

EVAL<\/h1>\n

PROLOG<\/a>
NAME<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
OPTIONS<\/a>
OPERANDS<\/a>
STDIN<\/a>
INPUT FILES<\/a>
ENVIRONMENT VARIABLES<\/a>
ASYNCHRONOUS EVENTS<\/a>
STDOUT<\/a>
STDERR<\/a>
OUTPUT FILES<\/a>
EXTENDED DESCRIPTION<\/a>
EXIT STATUS<\/a>
CONSEQUENCES OF ERRORS<\/a>
APPLICATION USAGE<\/a>
EXAMPLES<\/a>
RATIONALE<\/a>
FUTURE DIRECTIONS<\/a>
SEE ALSO<\/a>
COPYRIGHT<\/a> <\/p>\n

\n

PROLOG <\/a> <\/h2>\n

This manual page is part of the POSIX Programmer\u2019s 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.<\/p>\n

NAME <\/a> <\/h2>\n

eval \u2014 construct command by concatenating arguments<\/p>\n

SYNOPSIS <\/a> <\/h2>\n

eval [<\/b>argument<\/i>…]<\/b><\/p>\n

DESCRIPTION <\/a> <\/h2>\n

The eval<\/i> utility shall construct a command by concatenating argument<\/i>s together, separating each with a character. The constructed command shall be read and executed by the shell.<\/p>\n

OPTIONS <\/a> <\/h2>\n

None.<\/p>\n

OPERANDS <\/a> <\/h2>\n

See the DESCRIPTION.<\/p>\n

STDIN <\/a> <\/h2>\n

Not used.<\/p>\n

INPUT FILES <\/a> <\/h2>\n

None.<\/p>\n

ENVIRONMENT VARIABLES <\/a> <\/h2>\n

None.<\/p>\n

ASYNCHRONOUS EVENTS <\/a> <\/h2>\n

Default.<\/p>\n

STDOUT <\/a> <\/h2>\n

Not used.<\/p>\n

STDERR <\/a> <\/h2>\n

The standard error shall be used only for diagnostic messages.<\/p>\n

OUTPUT FILES <\/a> <\/h2>\n

None.<\/p>\n

EXTENDED DESCRIPTION <\/a> <\/h2>\n

None.<\/p>\n

EXIT STATUS <\/a> <\/h2>\n

If there are no argument<\/i>s, or only null argument<\/i>s, eval<\/i> shall return a zero exit status; otherwise, it shall return the exit status of the command defined by the string of concatenated argument<\/i>s separated by 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).<\/p>\n

CONSEQUENCES OF ERRORS <\/a> <\/h2>\n

Default.<\/p>\n

The following sections are informative.<\/i><\/p>\n

APPLICATION USAGE <\/a> <\/h2>\n

Since eval<\/i> is not required to recognize the “–“<\/b> end of options delimiter, in cases where the argument(s) to eval<\/i> might begin with \u2019-\u2019<\/b> it is recommended that the first argument is prefixed by a string that will not alter the commands to be executed, such as a character:<\/p>\n

eval ” $commands”<\/p>\n

or:<\/p>\n

eval ” $(some_command)”<\/p>\n

EXAMPLES <\/a> <\/h2>\n

foo=10 x=foo
y=’$’$x
echo $y
$foo<\/b>
eval y=’$’$x
echo $y
10<\/b><\/p>\n

RATIONALE <\/a> <\/h2>\n

This standard allows, but does not require, eval<\/i> to recognize “–“<\/b>. Although this means applications cannot use “–“<\/b> to protect against options supported as an extension (or errors reported for unsupported options), the nature of the eval<\/i> utility is such that other means can be used to provide this protection (see APPLICATION USAGE above).<\/p>\n

FUTURE DIRECTIONS <\/a> <\/h2>\n

None.<\/p>\n

SEE ALSO <\/a> <\/h2>\n

Section 2.14<\/i>, Special Built-In Utilities<\/i><\/p>\n

COPYRIGHT <\/a> <\/h2>\n

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 .<\/p>\n

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 .<\/p>\n

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