[زهراء المغرب]

http://www.commentcamarche.net/unix/unix-shell.php3
The command interpreter is the interface between the user and the operating system, hence its English name "shell", which means "shell".




The shell is responsible for the interface between the operating system and the user through the lines of commands entered by the latter. Its role is to read the command line, interpret its meaning, execute the command, and then return the result on the output.

The shell is an executable file to interpret the orders handed over to the system and return the result. There are several shells, the most common being sh (called "Bourne shell"), bash ( "Bourne again shell"), csh (C "Shell"), Tcsh (Tenex C shell), ksh ( "Korn shell" ) and zsh (Zero "shell"). Their name is usually in the name of the executable.

Each user has a default shell, which will be launched at the opening of a command prompt. The default shell is specified in the configuration file / etc / passwd in the last field of the line corresponding to the user. It is possible to change his shell in a session simply by running the corresponding executable file, for example:

/ Bin / bash