tcsh Command in Linux
The tcsh command in Linux starts the TC shell, which is an enhanced version of the C shell csh. It functions as both an interactive login shell and a script command processor. It features a command-line editor, programmable word completion, spelling correction, command history, job control, and C-style syntax.
Table of Contents
Here is a comprehensive guide to the options available with the tcsh command −
- Installation of tcsh Command
- Syntax of tcsh Command
- tcsh Command Options
- Examples of tcsh Command in Linux
Installation of tcsh Command
The tcsh command may not be installed by default on some Linux distributions. To install it on Ubuntu, Kali Linux, Raspberry Pi OS, Debian, and other Debian-based distributions, use the following command −
sudo apt install tcsh
To install it on Arch Linux, use the command given below −
sudo pacman -S tcsh
For Alpine Linux, use −
sudo apk add tcsh
To install tcsh on Fedora, use the following command −
sudo dnf install tcsh
To verify the installation of the tcsh command, check its version −
tcsh --version
Syntax of tcsh Command
The syntax of the tcsh command in Linux is given below −
tcsh [options] [script] [arguments]
In the above syntax, the [options] field is used to specify flags to modify shell behavior. The [script] field is used to specify the path to a .tcsh script to execute. The [arguments] field is used to mention script arguments. All fields are optional; however, in some contexts, for example, executing a script, specific fields are necessary.
tcsh Command Options
The options of the Linux tcsh command are listed below −
| Option | Description |
|---|---|
| -b | Stops option parsing; treats remaining arguments as positional. Required for set-user-ID scripts. |
| -c | Executes commands from the next argument; stores it in the command variable. |
| -d | Loads the directory stack from ~/.cshdirs on startup. |
| -Dname[=value] | Sets environment variable name to value (Domain/OS only). |
| -e | Exits on command failure or non-zero exit status. |
| -f | Skips startup files and hashing; faster startup. |
| -F | Uses fork() instead of vfork() to spawn processes. |
| -i | Forces interactive mode even if not connected to a terminal. |
| -l | Login shell mode (only if -l is the sole option). |
| -m | Loads ~/.tcshrc even if it belongs to a different user. |
| -n | Parses commands but does not execute; useful for debugging. |
| -q | Accepts SIGQUIT; disables job control for use with a debugger. |
| -s | Reads commands from standard input. |
| -t | Executes a single line of input; supports line continuation. |
| -v | Echoes commands after history substitution. |
| -x | Echoes commands before execution. |
| -V | Sets verbose mode before executing ~/.tcshrc. |
| -X | Like -x, but active before ~/.tcshrc. |
| --help | Displays help information and exits. |
| --version | Displays version and build info. |
Examples of tcsh Command in Linux
This section explains how to use the tcsh command in Linux with examples −
- Invoking the tcsh Interactive Shell
- Enable Verbose Mode Before Starting the tcsh Interactive Shell
- Executing a One-liner Command
- Running a tcsh Script
- Checking a tcsh Script for Syntax Errors without Executing
- Echoing Command before Executing the Script
- Invoking tcsh in Login Shell Mode
- Displaying Usage Help
Invoking the tcsh Interactive Shell
To invoke the tcsh interactive shell, use the tcsh command without any option −
tcsh
In the interactive tcsh shell, commands are typed directly at the prompt and executed when Enter is pressed, similar to other Unix shells.
Some basic examples are given below −
To set a variable −
set var = "tutorialspoint"
To print the variable, use echo −
echo $var
To perform an arithmetic operation −
set x=4 set y=3 @ sum = $x + $y echo $sum
To list the contents of a directory, use −
ls
To exit the interactive shell, type exit and press Enter.
Enable Verbose Mode Before Starting the tcsh Interactive Shell
To enable the verbose mode when starting the interactive shell, use the -V option −
tcsh -V
Any commands typed in the interactive session will be echoed back before execution.
Executing a One-liner Command
To run a one-liner command, use the -c option −
tcsh -c "echo Welcome to Tutorialspoint"
To list the directory −
tcsh -c "ls"
The -c option in tcsh allows the execution of a command string passed as an argument directly from the command line.
Running a tcsh Script
To execute a tcsh script, use the tcsh command followed by the script name −
tcsh myscript.tcsh "Hello TutorialsPoint"
Note that the string (Hello TutorialsPoint) after the script name in the above command is an argument.
The script and the output are shown in the following image −
Checking a tcsh Script for Syntax Errors without Executing
To check a tcsh script for syntax errors without executing it, use the -n option −
tcsh -n myscript.tcsh
Echoing Command before Executing the Script
To display commands before executing the script, use the -x option −
tcsh -x myscript.tcsh "Hello TutorialsPoint"
Invoking tcsh in Login Shell Mode
To start the shell in the login shell mode, use the -l option. A login shell is a type of shell session that runs specific startup scripts designed to configure the environment for the user.
tcsh -l
Displaying Usage Help
To print the usage help for the tcsh command, use the --help option −
tcsh --help
Conclusion
The tcsh command in Linux is an enhanced version of the C shell, offering features such as a command-line editor, programmable word completion, spelling correction, job control, and C-style syntax. It serves both as an interactive shell and a script processor, allowing users to execute commands, run scripts, and manage environments.
The tcsh command supports various options for customization, including running scripts, enabling verbose mode, and debugging.