Linux Shell Scripting
Overview
Shell scripting in Linux allows you to automate tasks and execute commands in a sequence. Shell scripts are written in various shell languages, such as Bash, and can simplify repetitive tasks and system administration.
Basic Concepts
Shebang
The shebang (#!
) specifies the interpreter for the script.
Example
Making a Script Executable
To make a script executable, use the chmod
command:
Example
Running a Script
To run a script, specify its path:
Example
Basic Script Elements
Variables
Variables store data and can be used throughout the script.
Example
Comments
Comments are added with the #
symbol and are ignored by the shell.
Example
Control Structures
Conditional Statements
Use if
, then
, elif
, and else
for conditional execution.
Example
#!/bin/bash
if [ -f "file.txt" ]; then
echo "file.txt exists."
else
echo "file.txt does not exist."
fi
Loops
Loops iterate over a set of commands.
for
Loop
Example
while
Loop
Example
Functions
Functions group commands and can be called multiple times.
Example
Advanced Topics
Command-Line Arguments
Access arguments passed to the script using $1
, $2
, etc.
Example
Redirection and Pipes
- Redirection:
>
to write output to a file,<
to read from a file.
- Pipes:
|
to pass the output of one command as input to another.
Example
Error Handling
Check the exit status of commands using $?
.
Example
Summary
Shell scripting is a powerful way to automate tasks and manage system operations. Understanding variables, control structures, loops, functions, and handling input/output will enable you to write effective scripts. For more detailed information, refer to the Bash manual or other shell scripting resources.