In this article, we will explain the basics of this command through some easy-to-understand examples. But before that, it’s worth pointing out that all examples presented below were tested under Ubuntu 16.04 LTS.
whereis command can help users find the binary file, source code and help page of a certain command. The following is its format:
whereis [options] [-BMS directory... -f] name...
This is the explanation given by the man page of this command:
whereis can find binary files, source files and help files for the specified command. The found files are displayed with the main pathname removed, and then with the file's (single) trailing extension (e.g.: .c) removed. The s. prefix originating from source control is also removed. Next, whereis will try to find the specific program in standard Linux locations, as well as in the paths specified by $PATH and $MANPATH.
The following examples in the form of Q&A can give you an intuitive feeling on how to use the whereis command.
Suppose you want to find, for example, your location with the whereis command. Here are your specific operations:
whereis whereis
It should be noted that the first path output is the result you want. Using the whereis command will also display the help page and source code path. (It will be displayed if it can be found, but it is not found in this example) So the second path you see in the output is the location of the help page file.
If you want to search only, say, binary files, you can use the -b command line option. For example:
whereis -b cp
Similarly, the two options -m and -s correspond to the help page and source code respectively.
By default, whereis looks for files from hard-coded paths defined by matchers. But if you want, you can limit the search with command line options. For example, if you only want to find binaries in /usr/bin, you can use the -B option to do so.
whereis -B /usr/bin/ -f cp
Note: Multiple paths can be given when using this method. Use the -f option to explicitly separate the directory listing and file names to search.
Similarly, if you want to search only help files or source code, you can use the -M and -S options accordingly.
There is also an option corresponding to this. Just add -l after whereis.
whereis -l
This is part of the output of the example:
For the whereis command, if a command has more than one item for each explicit request type, the command is considered an exception. For example, commands for which no documentation is available, or for which documentation is scattered throughout, can be counted as unusual commands. When using the -u option, whereis will display commands with exception entries.
For example, the following example shows that there is no corresponding document or a command with multiple documents in the current directory.
whereis -m -u *
I think whereis is not the kind of command line tool you need to use frequently. But it will definitely make your life easier when you encounter certain special situations. We've already touched on some of the important command line options this tool offers, so keep an eye on the exercise. For more information, go directly to its man page.
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