LINUX: Easy Linux For Beginners, Your Step-By-Step Guide to Learning The Linux Operating System and Command Line (2015)
Chapter Seven: Using the Linux Command Line
In Chapter Four, we discussed about the Linux Command Line or the terminal and how you can access it from your desktop. In the previous chapters, you were also able to use simple commands on the terminal. Each GUI action has a command-line equivalent. In this chapter, we will talk more about the different commands that you can use in Linux and also study the different shell features.
Using the Shell Features
You have now seen the capabilities of using the Bash shell. Performing tasks on the command line take lesser time than doing it in the GUI. To further enjoy the convenience of using the CLI (command line interface), here are some shell features that you should use:
· Command Completion
Launch a terminal and try typing an unfinished command.
For example, type the word below and press the Tab key.
unam
Notice that Linux will automatically complete the word to formuname. Next, remove the rest of the letters and just leave the letteru, Linux will then display all the list of commands that start with the letter ‘u’. This feature makes it even faster for a user to type commands. You can even do this for filenames or directory names too. Type the first few letters of the filename and Linux will do the rest for you.
This is also helpful when you are trying to remember a command since Linux will list out all the commands starting with the letters that you put in. Combine this functionality with man and you should be able to locate the command that you are looking for.
· Command History
Linux makes it easier for users too with the command history feature. The system remembers commands you have recently typed in so you no longer need to retype. Simply use the arrow keys to view previous commands.
Here are some of the techniques that you can use to make the most out of this feature:
Keys to Use |
What it does |
Arrow Up/Down |
Display the previous commands from the more recent going to the oldest entered |
Arrow Right/Left |
Moves the cursor one character to the right/left |
CTRL key + A |
Transfers cursor to the beginning of the line |
CTRL key + E |
Transfers cursor to the end of the line |
Delete key |
The character under the cursor is deleted |
Backspace |
The character to the left of the cursor is removed |
CTRL key + R |
Search for a particular command from the command history. After you use CTRL key + R, type the first few letters of the command that you want to use |
Table 9: Command Line History Shortcuts
System administrators make good use of these features because it makes admin tasks easier and faster to complete. Try the techniques on some of the commands you’ve learned and see how cool it is to work using the command line.
Essential Linux Commands
As a new Linux enthusiast, you can perform many of the tasks using the GUI. However, if you do fancy learning more commands that you can use in the shell prompt, here’s a cheat sheet of the most important Linux commands.
Command |
What it Does |
Help Commands |
|
info |
Shows online information about a command |
man |
Shows details of a command |
whatis |
Shows a short description of a specific keyword |
type |
Shows the location of a command file |
alias |
Assign a command alias – especially useful for long commands |
unalias |
Remove command alias |
Managing Files and Directories |
|
cd |
Change directory |
pwd |
Displays the current directory |
ln |
Create links to files and directories |
touch |
To trigger a file stamp update for a file |
Finding Files |
|
find |
Search for a file based on name |
whereis |
Search for executable files |
which |
Search for files in the directories part of the PATH variable |
Processing Files |
|
dd |
Copy lines of data |
diff |
Display the results of comparing two files |
more |
Show a text file one page at a time – display can only go forward |
less |
Show a text file one page at a time – display can only go forward and backwards |
wc |
Display the count of the number of characters, words, and lines in a file |
cat |
Show a text file in one output |
cut |
Get sections of text in a file |
grep |
Display results of finding expressions in a file |
sed |
Perform editing commands then copy to a standard output |
split |
Specify a size to break a file into |
sort |
Arrange the lines in a file |
uniq |
Keep unique lines in a file and delete duplicates |
Compressing a File |
|
compress |
Use to compress a file |
uncompress |
If a file was compressed with a compress command, use this to decompress |
gunzip |
Use GNU Zip to decompress files |
gzip |
Compress files with GNU Zip |
tar |
Archive files with one or more directories |
Date and Time |
|
cal |
Show the calendar for the specified month or year |
date |
Show/Set the current date and time |
Managing Processes |
|
bg |
Run a program or a process in the background |
free |
Check for the free memory |
kill |
Stop a process |
nice |
Run a program with a low priority |
ps |
Show current running processes |
top |
Show list of CPU and memory utilization of processes |
reboot |
Restart the computer |
shutdown |
Turn off computer |
Table 10: List of Important Linux Commands
Now, try out the commands above. If you are unsure of how to use the options for the commands, use the help commands (especially man and info) to find out more.
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In this chapter, I gave you a list of commands and techniques that you can try in the command line. Continue on practicing with these commands and to research more online. In the succeeding chapter, we will learn about securing your operating system.