Linux Commands

Simple list of Linux commands which are frequently used.

Introduction to the Unix/Linux command line. even if you are familiar with these bash commands its a good overview of all these commands.

Some Required Commands

Command Action Options
List ls -a (all files), -l (long format)
Make directory mkdir [OPT] DIR -p (make parents)
Change directory cd PATH . (current dir), .. (parent dir), ~ (home dir), - (last dir)
Print working directory pwd
Create empty file touch FILE
Copy cp [OPT] FROM TO -r (copy directories recursively)
Move or rename mv FROM TO
Remove rm [OPT] FILE -r (recursively remove directories), -f (force)
Remove directory rmdir [OPT] DIR -p (parents)
Concatenate and print files cat [OPT] FILES -l (number the output lines)
View file less [OPT] FILE -N (number the output lines)

Less Frequent Commands

Key Command Key Command
Space Next page /<text> Forward search for <text>
b Previous page ?<text> Backward search for <text>
j Next line n Next search match
k Previous line N Previous search match
g First line = File information
G Last line h Help
<n>G Line <n> q Quit
Command Action Options
Display first lines head [OPT] FILE -n (first n lines )
Display last lines tail [OPT] FILE -n (last n lines)
Print lines matching a pattern grep [OPT] PATTERN [FILE...] -c (display the number of matched lines), -i (ignore case sensitivity), -l (display the filenames), -n (display the line numbers), -w (match whole word)
Word count wc [OPT] FILE -l (line count), -c (byte count), -m (character count), -w (word count)

Control Key Commands

Command Action
Kill process CTRL + C
Stop process CTRL + Z
End of file CTRL + D

I/O Redirection

Redirection Action Description
STDOUT to a file COMMAND > FILE Overwrite
STDOUT to a file COMMAND >> FILE Append

In order to redirect the output from one command as input to the next one write COMMAND1 | COMMAND2 | COMMAND3.


Symbol Matches
* Any number of characters
? Any single character

System and Security

UNIX Permissions

sudo [OPT] [USER] COMMAND allows users to run programs with the security privileges of another user (normally the root).

u g o
user group others
r w x r w x r w x
4 2 1 4 2 1 4 2 1
7 7 7
Command Action Options
Change permissions chmod [OPT] MODE FILE -r (recursively)
Command MODE
Read and execute for all +rx
Deny write access for group g-w
Read, write and execute for all 777

UNIX Processes

Command Action Options
Run process in background COMMAND &
Background or suspended processes jobs
Send signal to a process kill SIGNAL PROCESS
Kill process by name killall PROCESS
Display top CPU processes top
Reports the process status ps -f (full listing), -e (all processes)


Command Action Options
Last commands used history -c (clear)
Last matched command !*
Time command execution time COMMAND
Compare files line by line diff
Walk a file hierarchy find PATH [OPT] [EXPRESSION] -name (find by name), -size (find by size), -iname (case sensitive mode)

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