whatis und apropos erklären einen Befehl kurz. Welches Programm man wann verwenden sollte, zeigt dieser Artikel.

# whatis bash
bash (1)             - GNU Bourne-Again SHell
# whatis shell
shell: nothing appropriate.
# apropos bash
bash (1)             - GNU Bourne-Again SHell
bashbug (1)          - report a bug in bash
# apropos shell
Shell (3pm)          - run shell commands transparently within perl
bash (1)             - GNU Bourne-Again SHell
chroot (1)           - run command or interactive shell with special root directory
chsh (1)             - change login shell
csh (1)              - C shell with file name completion and command line editing
dialog (1)           - display dialog boxes from shell scripts
in.rshd (8)          - remote shell server
rsh (1)              - remote shell
rshd (8)             - remote shell server
su (1)               - run a shell with substitute user and group IDs
tclsh (1)            - Simple shell containing Tcl interpreter
tcsh (1)             - C shell with file name completion and command line editing
XtCreatePopupShell (3x) - create a popup shell
XtVaCreatePopupShell (3x) - create a popup shell
wish (1)             - Simple windowing shell