Essential Linux Commands for Developers: A Comprehensive Guide
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Chapter 1: Introduction to Linux Commands
Linux is a widely utilized operating system among developers. Familiarizing yourself with essential Linux commands can significantly enhance your productivity.
Chapter 1.1: The Importance of Learning Linux Commands
Understanding Linux commands is crucial for effective system management. This article highlights several important commands that are beneficial to know.
Section 1.1.1: The Kill Command
The kill command is used to send signals to running processes. The basic syntax is:
kill <PID>
Where PID represents the process ID. You can use various signals, such as:
kill -HUP <PID>
kill -INT <PID>
kill -KILL <PID>
kill -TERM <PID>
kill -CONT <PID>
kill -STOP <PID>
- HUP (Hang Up): Sent when a terminal that started a process is closed.
- INT (Interrupt): Triggered by pressing Ctrl+C.
- KILL: Instructs the OS kernel to terminate the process.
- TERM (Terminate): Requests the process to terminate.
- CONT (Continue): Resumes a stopped process.
- STOP: Halts the process without terminating it.
Alternatively, you can use signal numbers: 1 for HUP, 2 for INT, 9 for KILL, 15 for TERM, and 18 for CONT.
Section 1.2: Monitoring Processes with Top
The top command allows you to view real-time running processes. You can exit top using Ctrl+C. To sort processes by memory usage, execute:
top -o mem
Chapter 2: Output and Process Management
Section 2.1: Using Echo for Output
The echo command outputs the arguments it receives. For example, you can write to a file like this:
echo "hello" >> output.txt
You can also include environment variables:
echo "path=$PATH"
Remember to escape special characters such as $. To display files in the current directory, use:
echo *
To echo files that begin with 'a':
echo a*
You can print your home directory path with:
echo ~
And display the results of a command using $():
echo $(ls)
Section 2.2: Listing Processes with PS
The ps command lists currently running processes. To view all processes, use:
ps ax
- a: Lists processes from all users.
- x: Displays processes not linked to any terminal.
- ww: Prevents output truncation.
The output includes various details, such as PID, terminal ID (TT), and process state (STAT). States include:
- I: Idle
- R: Runnable
- S: Sleeping (less than 20 seconds)
- T: Stopped
- U: Uninterruptible wait
- Z: Dead
Chapter 3: Creating Links with LN
The ln command is used to create links within the filesystem. The syntax is:
ln <source> <link>
For example:
ln foo.txt newfoo.txt
This creates a link named newfoo.txt that points to foo.txt. Links behave like regular files from the user's perspective.
Conclusion: Mastering Linux Commands
By learning these essential commands, you can effectively manage processes and create symbolic links in Linux.
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