shell commands..

The C shell provides the following built-in commands:
#
Marks a command.
alias
Displays alias.
bg
Resumes job in the background.
break
Resumes execution after the loop.
breaksw
Breaks from a switch command; resumes after the endsw command.
case
Defines a label in a switch command.
cd
Changes directory.
chdir
Changes directory, same as cd.
continue
Continues a loop.
default
Specifies the default case in a switch.
dirs
Displays the directory stack.
echo
Writes arguments to the standard output of the shell.
eval
Evaluates a command.
exec
Executes the command in the current shell.
exit
Exits the shell.
fg
Brings a job in the foreground.
foreach
Specifies a looping control statement and execute a sequence of commands until reaching an end command.
glob
Writes arguments to the standard output of the shell, like the echo command, but without the new line.
goto
Continues execution after the specified label.
hashstat
Displays hash table statistics.
history
Displays the history list.
if
Executes a command if condition met.
jobs
Lists active jobs.
kill
Sends a signal to a process. term (terminate) is the default signal.
limit
Sets or list system resource limits.
login
Logs on.
logout
Logs out.
nice
Changes the priority of commands run in the shell.
nohup
Ignores the hangup signal.
notify
Notifies the user about changes in job status.
onintr
Tells the shell what to do on interrupt.
popd
Pops the top directory off the directory stack and changes to the new top directory.
pushd
Exchanges the top two elements of the directory stack.
rehash
Re-computes the hash table of the contents of the directories in the path shell variable.
repeat
Repeats the execution of a command.
set
Displays or set the value of a shell variable.
setenv
Sets environment variables.
shift
Shifts shell arguments.
source
Reads commands from a script.
stop
Stops a background job.
suspend
Stops the current shell.
switch
Starts a switch.
time
Displays the time used to execute commands.
umask
Shows or set file permissions.
unalias
Removes command alias.
unhash
Disables the internal hash table.
unlimit
Removes limitations on system Resource.
unset
Deletes shell variables.
unsetenv
Deletes environment variables.
wait
Waits for background jobs to complete.
while …end
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.
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