The C shell provides the following built-in commands:
Marks a command.
Resumes job in the background.
Resumes execution after the loop.
Breaks from a switch command; resumes after the endsw command.
Defines a label in a switch command.
Changes directory, same as cd.
Continues a loop.
Specifies the default case in a switch.
Displays the directory stack.
Writes arguments to the standard output of the shell.
Evaluates a command.
Executes the command in the current shell.
Exits the shell.
Brings a job in the foreground.
Specifies a looping control statement and execute a sequence of commands until reaching an end command.
Writes arguments to the standard output of the shell, like the echo command, but without the new line.
Continues execution after the specified label.
Displays hash table statistics.
Displays the history list.
Executes a command if condition met.
Lists active jobs.
Sends a signal to a process. term (terminate) is the default signal.
Sets or list system resource limits.
Changes the priority of commands run in the shell.
Ignores the hangup signal.
Notifies the user about changes in job status.
Tells the shell what to do on interrupt.
Pops the top directory off the directory stack and changes to the new top directory.
Exchanges the top two elements of the directory stack.
Re-computes the hash table of the contents of the directories in the path shell variable.
Repeats the execution of a command.
Displays or set the value of a shell variable.
Sets environment variables.
Shifts shell arguments.
Reads commands from a script.
Stops a background job.
Stops the current shell.
Starts a switch.
Displays the time used to execute commands.
Shows or set file permissions.
Removes command alias.
Disables the internal hash table.
Removes limitations on system Resource.
Deletes shell variables.
Deletes environment variables.
Waits for background jobs to complete.
Executes the commands between the while and matching end statements repeatedly.
Displays or set the values of all the shell variables.
The Linux/Unix shell refers to a special program that allows you to interact with it by entering certain commands from the keyboard; the shell will execute the commands and display its output on the monitor. The environment of interaction is text-based (unlike the GUI-based interaction we have been using in the previous chapters) and since it is command-oriented this type of interface is termed Command Line interface or CLI. Before the advent of GUI-based computing environments, the CLI was the only way that one can interact and access a computer system.
Up until now, there was never a need to type commands into a shell; and with the modernisation and creation of a lot of newer GUI-based tools, the shell is becoming increasingly un-required to perform many tasks. But that said, the shell is a very powerful place, and a lot is achieved through it.