C Shell (csh)

History

The C Shell (csh) was developed by Bill Joy in the late 1970s at the University of California, Berkeley. It was designed to improve upon the Bourne Shell (sh) by providing a more user-friendly interface and incorporating features inspired by the C programming language, hence the name "C Shell."

Features

C-like Syntax: The syntax of csh is similar to the C programming language, making it easier for C programmers to use.
Job Control: Allows users to manage multiple processes within a single shell session.
History Mechanism: Enables users to recall and edit previous commands.
Aliases: Allows users to create shortcuts for frequently used commands.
Scripting: Supports writing scripts to automate tasks.

Basic Commands

pwd: Print the current working directory.
cd [directory]: Change the current directory to the specified directory.
ls: List the contents of the current directory.

File and Directory Management

touch [filename]: Create a new empty file.
mkdir [directory]: Create a new directory.
rm [filename]: Remove a file.
rmdir [directory]: Remove an empty directory.
cp [source] [destination]: Copy a file or directory.
mv [source] [destination]: Move or rename a file or directory.

Scripting

Basic Script

#!/bin/csh
# This is a comment
echo "Hello, World!"

Variables

#!/bin/csh
set name = "John"
echo "Hello, $name!"

Conditional Statements

#!/bin/csh
set number = 10
if ( $number > 5 ) then
  echo "The number is greater than 5"
else
  echo "The number is 5 or less"
endif

Loops

For Loop

#!/bin/csh
foreach i (1 2 3 4 5)
  echo "Iteration $i"
end

While Loop

#!/bin/csh
set counter = 1
while ( $counter <= 5 )
  echo "Counter: $counter"
  @ counter++
end

Functions

#!/bin/csh
alias greet 'echo Hello, \!*'

greet Alice
greet Bob

File Operations

Creating a File

#!/bin/csh
echo "This is a new file" > newfile.txt

Reading a File

#!/bin/csh
foreach line ( `cat newfile.txt` )
  echo $line
end

Deleting a File

#!/bin/csh
rm newfile.txt

Example: Backup Script

#!/bin/csh
set source_dir = "/path/to/source"
set backup_dir = "/path/to/backup"
set timestamp = `date +%Y%m%d%H%M%S`
set backup_file = "$backup_dir/backup_$timestamp.tar.gz"

tar -czf $backup_file $source_dir
echo "Backup created at $backup_file"

This script compresses the contents of the source directory into a tar.gz file and saves it in the backup directory with a timestamp.

Last modified: 14 December 2024

AICollection Help