Unset built-in

The unset built-in unsets variables or functions.

Synopsis

unset [-f|-v] name…

Description

The built-in unsets variables or functions named by the operands.

Options

Either of the following options may be used to select what to unset:

• The -v (--variables) option unsets variables. This is the default behavior.
• The -f (--functions) option unsets functions.

Operands

Operands are the names of variables or functions to unset.

Errors

Unsetting a read-only variable or function is an error.

It is not an error to unset a variable or function that is not set. The built-in ignores such operands.

The portable option causes additional errors; see Compatibility.

Exit status

Zero if successful; non-zero if an error occurs.

Examples

See Removing variables and Removing functions.

Compatibility

The unset built-in is specified by POSIX.1-2024.

The long option names (--functions, --variables) are a non-standard extension.

(Since 3.3.5) When the portable option is set, using a long option name is rejected with an error. Use the corresponding short option instead.

The behavior is not portable when both -f and -v are specified. Earlier versions of yash used to honor the last specified option, but this version errors out.

If neither -f nor -v is specified and the variable named by an operand is not set, POSIX allows the built-in to unset the same-named function if it exists. Yash does not do this.

POSIX requires that at least one operand be specified. By default, yash-rs allows the built-in to be called without any operands, in which case it does nothing. (Since 3.3.5) The portable option rejects this form with an error.

When a global variable is hidden by a local variable, the current implementation unsets the both. This is not portable. Old versions of yash used to unset the local variable only.