computing Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, hardware and softw ...

, which is a command for various

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

s used to identify the location of

executable In computer science, executable code, an executable file, or an executable program, sometimes simply referred to as an executable or binary, causes a computer "to perform indicated tasks according to encoded instruction (computer science), in ...

s. The command is available in

Unix Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...

and

Unix-like A Unix-like (sometimes referred to as UN*X, *nix or *NIX) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Uni ...

systems, the AROS shell, for FreeDOS and for

Microsoft Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

. The functionality of the ''which'' command is similar to some implementations of the type command.

POSIX The Portable Operating System Interface (POSIX; ) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines application programming interfaces (APIs), along with comm ...

specifies a command named command that also covers this functionality.

Implementations

Unix, Unix-like, Multics

The command takes one or more arguments; for each of these arguments, it prints the full path of the executable to stdout that would have been executed if this argument had been entered into the

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses Science Biology * Seashell, a hard outer layer of a marine ani ...

. It does this by searching for an executable or script in the directories listed in the environment variable PATH. The ''which'' command is part of most

computers. It is also part of the C Shell. A which command first appeared in 3BSD. Carlo Wood developed the GNU implementation used in most

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

-based operating systems. On FreeBSD, the which utility was originally written in

Perl Perl is a high-level, general-purpose, interpreted, dynamic programming language. Though Perl is not officially an acronym, there are various backronyms in use, including "Practical Extraction and Reporting Language". Perl was developed ...

by Wolfram Schneider. The current version of which was rewritten by Daniel Papasian using the C

programming language A programming language is a system of notation for writing computer programs. Programming languages are described in terms of their Syntax (programming languages), syntax (form) and semantics (computer science), semantics (meaning), usually def ...

Multics Multics ("MULTiplexed Information and Computing Service") is an influential early time-sharing operating system based on the concept of a single-level memory.Dennis M. Ritchie, "The Evolution of the Unix Time-sharing System", Communications of t ...

uses the command where abbreviated as wh.

Microsoft Windows, MS-DOS, FreeDOS

The command is available as a separate package for

as part of the GnuWin32 project and the UnxUtils collection of native Win32

ports Ports collections (or ports trees, or just ports) are the sets of makefiles and Patch (Unix), patches provided by the BSD-based operating systems, FreeBSD, NetBSD, and OpenBSD, as a simple method of installing software or creating binary packages. T ...

of common GNU

utilities A public utility company (usually just utility) is an organization that maintains the infrastructure for a public service (often also providing a service using that infrastructure). Public utilities are subject to forms of public control and r ...

. Windows also includes the similar where.exe command. The same functionality is available in

MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few op ...

, but not Windows, as the built-in TRUENAME command. In

PowerShell PowerShell is a shell program developed by Microsoft for task automation and configuration management. As is typical for a shell, it provides a command-line interpreter for interactive use and a script interpreter for automation via a langu ...

, the functionality is provided by the Get-Command Cmdlet. The FreeDOS version was developed by Trane Francks.

AmigaOS compatible

The command is used to find and print the location of a specific program. Inputs: * FILE – Specifies the command to search for * NORES – Resident programs are not included in the search * RES – Only resident programs are considered * ALL – Will find all locations of the FILE, which may cause the printing of the same location several times

References

External links

* * * * {{Unix commands Unix user management and support-related utilities