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Catalog / Tcsh Shell Scripting Cheatsheet

Tcsh Shell Scripting Cheatsheet

A comprehensive cheat sheet for Tcsh shell scripting, covering syntax, commands, and best practices to help you write effective and efficient scripts.

Tcsh Basics

Shell Invocation

tcsh - Starts a new Tcsh shell.
tcsh script.tcsh - Executes a Tcsh script.
tcsh -f script.tcsh - Executes script without sourcing .cshrc.
tcsh -x script.tcsh - Executes script with tracing (debugging).
tcsh -v script.tcsh - Executes script with verbose output.

Basic Syntax

#! /bin/tcsh

Shebang line, specifies the interpreter for the script.

set variable = value

Variable assignment.

echo $variable

Prints the value of a variable.

# comment

Single-line comment.

exit

Exits the script.

Input/Output Redirection

>

Redirects output to a file (overwrites).

>>

Appends output to a file.

<

Redirects input from a file.

|

Pipes output to another command.

Variables and Expressions

Variable Types

Tcsh primarily uses string variables. Numbers are also treated as strings unless used in numerical expressions.

Variable Assignment and Usage

set variable = value

Assigns value to variable.

set variable = ($item1 $item2 ...)

Assigns a list of items to variable.

echo $variable

Prints the value of the variable.

echo $variable[n]

Prints the nth element of the list variable (index starts at 1).

unset variable

Unsets a variable.

Expressions

@ variable = expression

Evaluates an arithmetic expression and assigns the result to variable.

@ variable++

Increments variable.

@ variable--

Decrements variable.

@ variable += value

Adds value to variable.

@ variable -= value

Subtracts value from variable.

Control Structures

Conditional Statements

if (condition) then commands endif

if (condition) then commands else commands endif

if (condition) then commands else if (condition) then commands else commands endif

Looping Statements

foreach variable (wordlist) commands end

while (condition) commands end

Switch Statement

switch (variable) case value1: commands breaksw case value2: commands breaksw default: commands breaksw endsw

Built-in Commands

File Manipulation

ls

Lists files and directories.

mkdir directory

Creates a new directory.

rm file

Removes a file.

rmdir directory

Removes an empty directory.

cp source destination

Copies a file.

mv source destination

Moves or renames a file.

Process Control

ps

Displays running processes.

kill pid

Terminates a process.

jobs

Lists background jobs.

fg %jobid

Brings a background job to the foreground.

bg %jobid

Sends a job to the background.

String Manipulation

string length $variable

Returns the length of the string in variable.

string index $variable position

Returns the character at the given position in the string.

string range $variable start end

Returns a substring from start to end index.
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