EVAL(1)                    POSIX Programmer's Manual                   EVAL(1)



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

NNAAMMEE
       eval -- construct command by concatenating arguments

SSYYNNOOPPSSIISS
       eval [[_a_r_g_u_m_e_n_t...]]

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

OOPPTTIIOONNSS
       None.

OOPPEERRAANNDDSS
       See the DESCRIPTION.

SSTTDDIINN
       Not used.

IINNPPUUTT FFIILLEESS
       None.

EENNVVIIRROONNMMEENNTT VVAARRIIAABBLLEESS
       None.

AASSYYNNCCHHRROONNOOUUSS EEVVEENNTTSS
       Default.

SSTTDDOOUUTT
       Not used.

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

OOUUTTPPUUTT FFIILLEESS
       None.

EEXXTTEENNDDEEDD DDEESSCCRRIIPPTTIIOONN
       None.

EEXXIITT SSTTAATTUUSS
       If there are no _a_r_g_u_m_e_n_ts, or only null _a_r_g_u_m_e_n_ts, _e_v_a_l shall return a
       zero exit status; otherwise, it shall return the exit status of the
       command defined by the string of concatenated _a_r_g_u_m_e_n_ts 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).

CCOONNSSEEQQUUEENNCCEESS OOFF EERRRROORRSS
       Default.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       Since _e_v_a_l is not required to recognize the ""----"" end of options
       delimiter, in cases where the argument(s) to _e_v_a_l 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)"

EEXXAAMMPPLLEESS
       foo=10 x=foo
       y='$'$x
       echo $y
       $$ffoooo
       eval y='$'$x
       echo $y
       1100

RRAATTIIOONNAALLEE
       This standard allows, but does not require, _e_v_a_l 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 _e_v_a_l utility is such that other means can
       be used to provide this protection (see APPLICATION USAGE above).

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _S_e_c_t_i_o_n _2_._1_4, _S_p_e_c_i_a_l _B_u_i_l_t_-_I_n _U_t_i_l_i_t_i_e_s

CCOOPPYYRRIIGGHHTT
       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 .



IEEE/The Open Group                  2017                              EVAL(1)
