CentOS 6.3 / RHEL 6.3
Can someone please explain the difference between the
whatis command and the
apropos command? I noticed that both appear to be installed by default and I'm not sure what the difference is between them.
whatis displays one-line manual page descriptions, intended to give you a general idea of what a program do,
apropos searches the manual page names and descriptions, intended to help you to learn what program to use when performing a certain job.
Say, I want to know what does
df program do.
whatis gives me answer.
$ whatis df df (1) - report file system disk space usage
And now, I want to unzip an archive.
apropos gives me some choises for consideration.
$ apropos unzip bunzip2 (1) - a block-sorting file compressor, v1.0.6 funzip (1) - filter for extracting from a ZIP archive in a pipe gunzip (1) - compress or expand files lz (1) - gunzips and shows a listing of a gzip'd tar'd archive preunzip (1) - prefix delta compressor for Aspell unzip (1) - list, test and extract compressed files in a ZIP archive unzipsfx (1) - self-extracting stub for prepending to ZIP archives uz (1) - gunzips and extracts a gzip'd tar'd archive
apropos search man database, you can only get info on what's already installed on your system.
whatis ls lists the manual pages for
apropos ls lists all manual pages that contain
ls in their title. The first list here gives 2 entries, the second 1385.
they act the same with one different: whatis need a accurate parameter:
But apropos need a string or first characters of something that you know: