Saturday, April 23, 2011

Linux Basic Commands

Sources to learn commands??

Primary – man(manual) pages.
 man <command> shows all information about the command
 <command> help shows the available options for that command
 Secondary – Books and Internet

File Handling commands

mkdir – make directories
Usage: mkdir [OPTION] DIRECTORY...
eg. mkdir prabhat
ls – list directory contents
Usage: ls [OPTION]... [FILE]...
eg. ls, ls l,
ls prabhat
cd – changes directories
Usage: cd [DIRECTORY]
eg. cd prabhat

• pwd print
name of current working directory
Usage: pwd
vim – Vi Improved, a programmers text editor
Usage: vim [OPTION] [file]...
eg. vim file1.txt
cp – copy files and directories
eg. cp sample.txt sample_copy.txt
cp sample_copy.txt target_dir
mv – move (rename) files
eg. mv source.txt target_dir
mv old.txt new.txt
rm remove files or directories
Usage: rm [OPTION]... FILE...
eg. rm file1.txt , rm -rf some_dir
find – search for files in a directory hierarchy
Usage: find [OPTION] [path] [pattern]
eg. find file1.txt, find name file1.txt
history – prints recently used commands
Usage: history

A Pattern is an expression that describes a set of strings which is used to give a concise description of a set, without having to list all elements.
eg. ab*cd matches anything that starts with ab and ends with cd etc.
ls *.txt – prints all text files

Text Processing
• cat – concatenate files and print on the standard output
Usage: cat [OPTION] [FILE]...
eg. cat file1.txt file2.txt
cat n file1.txt
• echo – display a line of text
Usage: echo [OPTION] [string] ...
eg. echo I love India
echo $HOME
• grep print
lines matching a pattern
Usage: grep [OPTION] PATTERN [FILE]...
eg. grep i
apple sample.txt
• wc print
the number of newlines, words, and bytes in files
Usage: wc [OPTION]... [FILE]...
eg. wc file1.txt
wc L file1.txt
• sort – sort lines of text files
Usage: sort [OPTION]... [FILE]...
eg. sort file1.txt
sort r file1.txt

Linux File Permissions
• 3 types of file permissions – read, write, execute
• 10 bit format from 'ls l'
1 2 3 4 5 6 7 8 9 10
file type owner group others
eg. drwxrwrmeans
owner has all three permissions,
group has read and write, others have only read
• read permission – 4, write – 2, execute 1
eg. rwxrwr=
673 = rwrwxwx

System Administration
chmod – change file access permissions
Usage: chmod [OPTION] [MODE] [FILE]
eg. chmod 744
• chown – change file owner and group
Usage: chown [OPTION]... OWNER[:[GROUP]] FILE...
eg. chown remo myfile.txt
• su – change user ID or become superuser
Usage: su [OPTION] [LOGIN]
eg. su remo, su
• passwd – update a user’s authentication tokens(s)
Usage: passwd [OPTION]
eg. passwd
• who – show who is logged on
Usage: who [OPTION]
eg. who , who b, who q

Process Management

• ps – report a snapshot of the current processes
Usage: ps [OPTION]
eg. ps, ps el
• kill – to kill a process(using signal mechanism)
Usage: kill [OPTION] pid
eg. kill 9 2275


• tar – to archive a file
eg. tar cvf
/home/archive.tar /home/original
tar xvf 


• zip – package and compress (archive) files
eg. zip original
• unzip – list, test and extract compressed files in a ZIP archive
Usage: unzip filename
eg. unzip

• ssh – SSH client (remote login program)
“ssh is a program for logging into a remote machine and for
executing commands on a remote machine”
Usage: ssh [options] [user]@hostname
eg. ssh X guest@
• scp – secure copy (remote file copy program)
“scp copies files between hosts on a network”
Usage: scp [options] [[user]@host1:file1] [[user]@host2:file2]
eg. scp file1.txt guest@

File Systems
• fdisk – partition manipulator
eg. sudo fdisk l
• mount – mount a file system
Usage: mount t type device dir
eg. mount /dev/sda5 /media/target
• umount – unmount file systems
Usage: umount [OPTIONS] dir | device...
eg. umount /media/target
• du – estimate file space usage
Usage: du [OPTION]... [FILE]...
eg. du
• df – report filesystem disk space usage
Usage: df [OPTION]... [FILE]...
eg. df
• quota – display disk usage and limits
Usage: quota [OPTION]
eg. quota v

Advanced Commands
• reboot – reboot the system
Usage: reboot [OPTION]
eg. reboot
• poweroff – power off the system
Usage: poweroff [OPTION]
eg. poweroff

Editor commands
• kate – KDE Advanced Text Editor
Usage: kate [options][file(s)]
eg. kate file1.txt file2.txt
• vim – Vi Improved, a programmers text editor
Usage: vim [OPTION] [file]...
eg. vi hello.c
• gedit A
text Editor. Used to create and edit files.
Usage: gedit [OPTION] [FILE]...
eg. gedit

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