Bourne Shell (sh)

History

The Bourne Shell (sh) was developed by Stephen Bourne at AT&T Bell Laboratories and released in 1979 as the default Unix shell in Version 7 Unix. It was designed to be a command interpreter and scripting language, providing a way to automate tasks and manage system operations. The Bourne Shell has influenced many other shells, including the Korn Shell (ksh) and the Bourne Again Shell (bash).

Features

Scripting: Supports writing scripts to automate tasks.
Command Substitution: Allows the output of a command to replace the command itself.
Control Structures: Provides constructs for conditional execution and loops.
Variables: Supports the use of variables to store data.
Redirection: Allows input and output redirection for commands.
Pipelines: Supports chaining commands together using pipes.

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

Variables

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

Conditional Statements

#!/bin/sh
number=10
if [ $number -gt 5 ]; then
  echo "The number is greater than 5"
else
  echo "The number is 5 or less"
fi

Loops

For Loop

#!/bin/sh
for i in 1 2 3 4 5; do
  echo "Iteration $i"
done

While Loop

#!/bin/sh
counter=1
while [ $counter -le 5 ]; do
  echo "Counter: $counter"
  counter=$((counter + 1))
done

Functions

#!/bin/sh
greet() {
  echo "Hello, $1!"
}

greet "Alice"
greet "Bob"

File Operations

Creating a File

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

Reading a File

#!/bin/sh
while IFS= read -r line; do
  echo "$line"
done < newfile.txt

Deleting a File

#!/bin/sh
rm newfile.txt

Example: Backup Script

#!/bin/sh
source_dir="/path/to/source"
backup_dir="/path/to/backup"
timestamp=$(date +%Y%m%d%H%M%S)
backup_file="$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