I am using RASPBIAN on my raspberry pi. I find out that the command "apropos" is a symbolic link of the command "wahtis". However, the output of those commands do not match when used with the same arguments:
$ whatis delete delete: nothing appropriate.
$ apropos delete argz_delete (3) - functions to handle an argz list delete_module (2) - unload a kernel module dphys-swapfile (8) - set up, mount/unmount, and delete an swap file git-branch (1) - List, create, or delete branches git-replace (1) - Create, list, delete refs to replace objects git-symbolic-ref (1) - Read, modify and delete symbolic refs git-tag (1) - Create, list, delete or verify a tag object signed ***output is truncated to save space....***
It is clear that the apropos is a symbolic link of whatis.
pi@raspberry:~ $ which apropos /usr/bin/apropos pi@raspberry:~ $ ls -l /usr/bin/apropos lrwxrwxrwx 1 root root 6 Aug 24 2017 /usr/bin/apropos -> whatis
How can that happen?