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man pages section 1: User Commands

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Updated: Wednesday, February 9, 2022



builtin - ksh built-in function to add, delete, or display shell built-ins


builtin [-ds] [-f lib] [pathname ...]


The ksh builtin command adds, deletes, or displays built-in commands in the current shell environment. A built-in command executes in the current shell process and can have side effects in the current shell. On most systems, the invocation time for built-in commands is one or two orders of magnitude less than commands that create a separate process.

For each pathname specified, the basename of the pathname determines the name of the built-in. For each basename, the shell looks for a C level function in the current shell whose name is determined by pre-pending b_ to the built-in name. If pathname contains a forward slash (/), the built-in is bound to pathname. A built-in bound to a pathname is only executed if pathname is the first executable found during a path search. Otherwise, built-ins are found prior to performing the path search.

If pathname is not specified, builtin displays the current list of built-ins, or just the special built-ins if the –s option is specified, on standard output. The full pathname for built-ins that are bound to pathnames are displayed.

Libraries containing built-ins can be specified with the –f option. If the library contains a function named lib_init(), this function is invoked with argument 0 when the library is loaded. The lib_init() function can load built-ins by invoking an appropriate C level function. In this case there is no restriction on the C level function name.

The C level function is invoked with three arguments. The first two are the same as main() and the third one is a pointer.

The ksh builtin command cannot be invoked from a restricted shell.


The following options are supported:


Delete each of the specified built-ins. Special built-ins cannot be deleted.

–f lib

On systems with dynamic linking, load and search for built-ins in the shared library, lib.

Libraries are searched for in $PATH and system dependent library directories. The system dependent shared library prefix or suffix can be omitted. Once a library is loaded, its symbols become available for the current and subsequent invocations of builtin. Multiple libraries can be specified with separate invocations of builtin. Libraries are searched in the reverse order in which they are specified.


Display only the special built-ins.


The following operands are supported:


Specifies the pathname. The basename of the pathname determines the name of the built-in.

Exit Status

The following exit values are returned:


Successful completion.


An error occurred.


Example 1 Loading a builtin Command

The following example loads a builtin command mycmd from the library libfoo.so:

example% builtin -f foo mycmd


David Korn, dgk@research.att.com


See attributes(7) for descriptions of the following attributes:

Interface Stability

See Also

ksh(1), whence(1), attributes(7)