unset

This article is about Unix command. For the town in Hedmark, see Unset, Norway. For the novelist, see Sigrid Undset.

unset is a builtin Unix shell command implemented by both the Bourne shell family of shells (sh, ksh, bash, etc.) and the C shell family of shells (csh, tcsh, etc.). It unsets a shell variable, removing it from memory and the shell's exported environment. It is implemented as a shell builtin, because it directly manipulates the internals of the shell.

Read-only shell variables cannot be unset. If one tries to unset a read-only variable, the unset command will print an error message and return a non-zero exit code. For more information on read-only variables, see readonly.

See also

• List of Unix programs

External links

• unset: unset values and attributes of variables and functions – Commands & Utilities Reference, The Single UNIX® Specification, Issue 7 from The Open Group