whence

whence [-afpv] name...whence [-vcwfpamsS] [-x num] name... (zsh)

whence is a shell builtin in ksh and zsh that reports how each name would be interpreted if used as a command. Unlike the external which utility, it understands shell aliases, functions, builtins, reserved words, and hashed commands, not only executables on PATH.With no options, whence typically prints the resolved path for external commands or an indication of the alias or other shell object. -v adds a descriptive message similar to type or command -V. -p forces a filesystem PATH search when a name is shadowed by a shell construct.In zsh, whence is the underlying implementation for several related builtins:- which is equivalent to whence -c- where is equivalent to whence -ca- type is equivalent to whence -vksh provides a smaller option set (-a, -f, -p, -v). bash and POSIX shells do not provide whence; use type, command -v, or command -V there instead.

-v

Produce a more verbose report

Report all interpretations / search the entire command path (not only the first match)

Do a PATH search even if name is an alias, reserved word, function, or builtin

Skip the search for shell functions (ksh). In zsh, with -c, display the contents of a shell function

Print results in a csh-like format (takes precedence over -v). Equivalent to the zsh which builtin when used alone

Print `name: word` where word is one of: alias, builtin, command, function, hashed, reserved, or none

Treat arguments as patterns and display matching commands (quote pattern characters)

If a pathname contains symlinks, also print the symlink-free pathname

Like -s, but print intermediate symlink resolution steps

Expand tabs when outputting shell functions with -c (same idea as functions -x)

Resolve commands in zsh

$ $ whence ls
/bin/ls

$ whence -v ls
ls is /bin/ls

$ whence -w cd
cd: builtin

$ whence -w for
for: reserved

$ $ whence -a python3

0

Name was found (recognized as a command form the shell understands)

Name was not recognized. In zsh, a not-found message for -v, -c, or -w is written to standard output (not standard error), which differs from some other shells

whence is not a standalone program and is not available in bash or plain sh. Scripts that need portability should prefer command -v (POSIX) or type.Pattern matching with -m (zsh) only applies to the final path component of a command name; pass the basename, not a full path with `/`.Option letters and output formats differ between ksh and zsh. Features such as -c, -w, -m, -s, and -S are zsh extensions.

whence originates in the KornShell (ksh) as the shell's command-lookup reporter. zsh adopted it and built a richer interface on top, with which, where, and type implemented as variants of whence. It is not specified by POSIX.

type(1), which(1), command(1), hash(1), whereis(1)

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