eval — Construct a command by concatenating arguments

Format

eval [argument …]

tcsh shell: eval argument …

Description

The shell evaluates each argument as it would for any command. eval then concatenates the resulting strings, separated by spaces, and evaluates and executes this string in the current shell environment.

In the tcsh shell, eval treats the arguments as input to the shell and executes the resulting commands in the context of the current shell. This action is typically used to execute commands generated as the result of command or variable substitution, since parsing occurs before these substitutions. See tcsh — Invoke a C shell.

Examples

The command:

for a in 1 2 3
do
        eval x$a=fred
done

sets variables x1, x2, and x3 to fred. Then:

echo $x1 $x2 $x3

produces:

fred fred fred

Usage notes

eval is a special built-in shell command.

Localization

eval uses the following localization environment variables:

LANG
LC_ALL
LC_MESSAGES
NLSPATH

See Localization for more information.

Exit values

The only possible exit status value is:

0: No arguments were specified, or the specified arguments were empty strings

Otherwise, the exit status of eval is the exit status of the command that eval runs.

Portability

POSIX.2, X/Open Portability Guide, UNIX systems.

Related information

exec, sh, tcsh