Master Linux: When to Use which, whereis, and whatis Commands

which

The which command searches the directories listed in the PATH environment variable and returns the path of the first matching executable. Example: which python This prints the full path to the Python interpreter that would be executed when you type python in the shell.

whereis

The whereis command extends the search to standard system directories and can locate binaries, manual pages, and source files. Example: whereis python The output shows the locations of the Python binary, its man page, and any source files, making it useful for finding related resources beyond PATH.

whatis

The whatis command provides a one‑line description of a command’s purpose, pulling from the manual page’s NAME section. Example: whatis python The result is a brief summary such as “python – an interpreted, interactive, object‑oriented programming language”, which is handy for quick reference.

Understanding the differences— which for executable location, whereis for broader resource locations, and whatis for concise descriptions—helps Linux users locate and identify commands efficiently.