1EVAL(1P) POSIX Programmer's Manual EVAL(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 eval — construct command by concatenating arguments
14
16 eval [argument...]
17
19 The eval utility shall construct a command by concatenating arguments
20 together, separating each with a <space> character. The constructed
21 command shall be read and executed by the shell.
22
24 None.
25
27 See the DESCRIPTION.
28
30 Not used.
31
33 None.
34
36 None.
37
39 Default.
40
42 Not used.
43
45 The standard error shall be used only for diagnostic messages.
46
48 None.
49
51 None.
52
54 If there are no arguments, or only null arguments, eval shall return a
55 zero exit status; otherwise, it shall return the exit status of the
56 command defined by the string of concatenated arguments separated by
57 <space> characters, or a non-zero exit status if the concatenation
58 could not be parsed as a command and the shell is interactive (and
59 therefore did not abort).
60
62 Default.
63 The following sections are informative.
65
67 Since eval is not required to recognize the "--" end of options delim‐
68 iter, in cases where the argument(s) to eval might begin with '-' it is
69 recommended that the first argument is prefixed by a string that will
70 not alter the commands to be executed, such as a <space> character:
71 eval " $commands"
73 or:
75 eval " $(some_command)"
77
79 foo=10 x=foo
80 y='$'$x
81 echo $y
82 $foo
83 eval y='$'$x
84 echo $y
85 10
86
88 This standard allows, but does not require, eval to recognize "--".
89 Although this means applications cannot use "--" to protect against
90 options supported as an extension (or errors reported for unsupported
91 options), the nature of the eval utility is such that other means can
92 be used to provide this protection (see APPLICATION USAGE above).
93
95 None.
96
98 Section 2.14, Special Built-In Utilities
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101 Portions of this text are reprinted and reproduced in electronic form
102 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
103 -- Portable Operating System Interface (POSIX), The Open Group Base
104 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
105 cal and Electronics Engineers, Inc and The Open Group. (This is
106 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
107 event of any discrepancy between this version and the original IEEE and
108 The Open Group Standard, the original IEEE and The Open Group Standard
109 is the referee document. The original Standard can be obtained online
110 at http://www.unix.org/online.html .
111 Any typographical or formatting errors that appear in this page are
113 most likely to have been introduced during the conversion of the source
114 files to man page format. To report such errors, see https://www.ker‐
115 nel.org/doc/man-pages/reporting_bugs.html .
116IEEE/The Open Group 2013 EVAL(1P)