The whatis command

# whatis

Whatis accepts the name of another command as its only argument. It then searches for the given command name in a database of short descriptions. If it finds a match, the description is printed to your screen. Along with the description ,  whatis  prints the command’s name and a number in parenthesis. The database that whatis uses re-generated automatically every night. This means that newly-installed systems whatis will not work at first because the database does not yet exist; the impatient can generate a database without waiting for the automatic update by asking an administrator to log in and run

# makewhatis.

whatis command updating

Example:

[root@localhost  ~]# whatis  cal 

Cal                                          (1)      – displays a calendar
cal                                           (1p)    – print a calendar

whatis command