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What's the difference between which and whereis ?

Shekhar
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mk12
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  • I'm sorry but on my 10.5.8 OS X system which and whereis **always** give the same results. Maybe this *is* a very OS X specific question, since I agree, a different result is expected. Maybe whereis does not comply to what it should do. At least the two examples (see below) are not working: whereis ls and whereis php always give the same result as which ... Can anybody confirm this? Does Snow Leopard behave the same? – Wolf Sep 12 '09 at 23:11
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    Yeah I know, thats why I asked this question. – mk12 Sep 12 '09 at 23:25
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    @mk12 I feel like `type` is superior. It also knows about defined aliases, functions etc – phil294 Aug 19 '18 at 03:32

4 Answers4

174

How about learning about whereis and which using whatis?

$  whatis which
which                (1)  - shows the full path of (shell) commands

$  whatis whereis
whereis              (1)  - locate the binary, source, and manual page files for a command

Basically, whereis searches for "possibly useful" files, while which only searches for executables.

I rarely use whereis. On the other hand, which is very useful, specially in scripts. which is the answer for the following question: Where does this command come from?

$  which ls
/bin/ls

$  whereis ls
ls: /bin/ls /usr/share/man/man1p/ls.1p.bz2 /usr/share/man/man1/ls.1.bz2
Denilson Sá Maia
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    There's more to it than that. On my system, whereis and which return different executable paths. I can only get the path to the one that actually runs with `whereis`, not the one for `which`. – Jordan Reiter Aug 21 '16 at 22:25
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    @JordanReiter: It can't be! `which` shows the actual path. Are you sure the path pointed by `which` isn't just a symlink to the path pointed by `whereis`? Maybe it is a shell alias. In bash, try running `type your_cmd_here`. – Denilson Sá Maia Aug 22 '16 at 00:01
  • @DenilsonSá unfortunately I can't recreate the situation but when I run into it again I'll provide more details. – Jordan Reiter Sep 01 '16 at 18:14
  • @DenilsonSáMaia, I get the same thing. ```$ type xcodebuild --> xcodebuild is hashed (/usr/local/bin/xcodebuild) $ which xcodebuild --> /usr/local/bin/xcodebuild $ whereis xcodebuild --> /usr/bin/xcodebuild``` And running `xcodebuild` always picks the wrong one (i.e., the `/usr/bin` command) even though `/usr/local/bin` has higher `$PATH` priority. – SO_fix_the_vote_sorting_bug May 30 '18 at 21:32
  • I have mutliple python installations. Some in `/usr/bin/python2.7`, some in `/usr/local/lib/python3.4`. `whereis python` finds them both which is a great way to list all python versions installed – lucidbrot Aug 24 '19 at 13:45
  • `which ls` and `whereis ls` show the same results for me, on OSX 10.15.4 – edan Jun 19 '20 at 18:34
  • On macOS, `whereis` searches only for _programs_ and not man pages or sources; it does this in "standard binary directories"; while `which` searches for programs in current `PATH`. Of course, macOS isn't *nix strictly. – legends2k Dec 22 '20 at 16:12
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whereis searches the standard *nix locations for a specified command.

which searches your user-specific PATH (which may include some of the locations whereis searches, and may not include others - it might also include some places that whereis doesn't search if you'd added to your PATH)

Amber
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    Unix, Linux etc. (Mac OS X belonging in the etc.) –  Sep 12 '09 at 20:23
  • Nope. Just a fairly common convention of creative wildcard use to refer to a family of similar operating systems. ;) –  Sep 12 '09 at 22:28
  • Yes! For a good example, compare: `PATH='' /usr/bin/which vim` vs `PATH='' /usr/bin/whereis vim`. The `whereis` command still locates the executable, even if your PATH is empty. – edan Jun 19 '20 at 18:35
7

Quoting their man pages :

whereis :

whereis locates source/binary and manuals sections for specified files.

For instance :

$ whereis php
php: /usr/bin/php /usr/share/php /usr/share/man/man1/php.1.gz

ie, the "php" executable, and some other stuff (like man pages).


and which :

which returns the pathnames of the files which would be executed in the current environment

For instance : 

$ which php
/usr/bin/php

ie, only the "php" executable.

Pascal MARTIN
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which search for executables in the directories specified by the environment variable PATH. And if found out, the full pathname of this executable will be printed.

$ which ls
/bin/ls
$ which ifconfig
$ # No output, because ifconfig only exist in root's PATH.

whereis search for executables, source files, and manual pages using a database built by system automatically.

$ whereis less
less: /bin/less /usr/bin/less /usr/bin/X11/less /usr/share/man/man1/less.1.gz

But it seems that whereis and locate don't use the same database. When I installed a software and then used whereis and locate immediately to search for this software. The result is that whereis could find out some files related to this software while locate couldn't. Do they really use different database? How the database work? --Well, how about refuse to be a pedant? :)

user192505
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