Typically, eval is used in shell scripts,
args is a line of code that contains shell variables.
eval forces variable expansion to happen first
and then runs the resulting command.
This "double-scanning" is useful any time shell variables
contain input/output redirection symbols, aliases, or other shell variables.
(For example, redirection normally happens before variable
expansion, so a variable containing redirection symbols must be
expanded first using eval; otherwise, the redirection symbols
A Bourne shell example can be found under eval in Section 4.
Other uses of eval are shown below and under alias.
The following lines can be placed in the .login file to set up terminal characteristics:
set noglob eval `tset -s xterm` unset noglob
The following commands show the effect of eval:
echo $bRead the command line once. $a %
eval echo $bRead the command line twice. hello