What's what – which, whereis, whatis, and file
There may be several files with the same name. Knowing which executable is being invoked and whether a file is compiled code or a script is useful information.
How to do it...
The which
, whereis
, file
, and whatis
commands report information about files and directories.
which
: The which command reports the location of a command:
$ which ls /bin/ls
- We often use commands without knowing the directory where the executable file is stored. Depending on how your
PATH
variable is defined, you may use a command from/bin
,/usr/local/bin
, or/opt/PACKAGENAME/bin
. - When we type a command, the terminal looks for the command in a set of directories and executes the first executable file it finds. The directories to search are specified in the
PATH
environment variable:
$ echo $PATH /usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
- We can add directories to be searched and export the new
PATH
. To add/opt/bin
toPATH
, use the following command...