"Useful Commands For The Linux Command Line"

arch

Outputs the processor architecture.

$ arch

i686

cat

Outputs the contents of a file.

$ cat lorem.txt

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

cd

Change the working directory.

$ cd /bin

chgrp

Change group ownership of files.

$ chgrp games moo.txt

chmod

Change access permissions of files.

$ chmod +x helloworld

chown

Change file owner and group.

# chown root lorem.txt

cksum

Print CRC checksum and byte counts of each file.

$ cksum lorem.txt moo.txt

3570240675 453 lorem.txt

4294967295 0 moo.txt

cp

Copies a file.

$ cp lorem.txt copy_of_lorem.txt

date

Outputs the current date and time.

$ date

Sat Mar  3 12:07:09 GMT 2007

df

Reports the amount of disk space used and available on filesystems.

$ df

Filesystem           1K-blocks      Used Available Use% Mounted on<br>

/dev/simfs            39845888    218048  39627840   1% /

dir

List directory contents.

$ dir

copy_of_lorem.txt  lorem.txt  moo.txt  www

du

Estimate file space usage.

$ du -h /bin

7.8M    /bin

echo

Display a line of text.

$ echo foobar

foobar

exit

Cause the shell to exit.

$ exit

fgrep

Print lines matching a pattern in a file.

$ fgrep “irure dolor” lorem.txt

commodo consequat. Duis aute irure dolor in reprehenderit in voluptate

find

Search for files in a directory hierarchy.

$ find hello*

hello_world

hello_world.c

free

Display amount of free and used memory in the system.

$ free

                       total       used       free     shared    buffers     cached

Mem:       8299892    8287708      12184          0    2641772    1731236

Low:       3581300    3572764       8536

High:      4718592    4714944       3648

-/+ buffers/cache:    3914700    4385192

Swap:      8193140    2335664    5857476

grep

Print lines matching a pattern.

$ grep -i apple fruitlist.txt

apple

groups

Outputs the user groups of which your account belongs to.

$ groups

games users

head

Output the first part of files.

$ head -2 lorem.txt

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod

tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim

hostname

Outputs the machines hostname on the network.

$ hostname

anapnea.net

id

Outputs user id, group id, and groups of your account.

$ id

uid=1478(smallfoot) gid=100(users) groups=35(games),100(users)

kill

End a process.

$ kill -9 18298

-bash: kill: (18298) – Operation not permitted

killall

Kill processes by name.

$ killall irssi

irssi(18298): Operation not permitted

irssi(13372): Operation not permitted

irssi(22048): Operation not permitted

irssi: no process killed

last

Show listing of last logged in users.

$ last -n 3

alice    pts/6        192.0.34.166     Fri May 18 16:17   still logged in

bob      pts/2        64.233.183.103   Fri May 18 16:17   still logged in

clare    pts/6        72.5.124.61      Fri May 18 15:54 – 15:55  (00:01)

ldd

Print shared library dependencies.

$ ldd /bin/bash

        libncurses.so.5 => /lib/libncurses.so.5 (0×40023000)

        libdl.so.2 => /lib/libdl.so.2 (0×40065000)

        libc.so.6 => /lib/libc.so.6 (0×40069000)

        /lib/ld-linux.so.2 (0×40000000)

ln

Make links between files.


$ ln -s data.txt symlink.txt


logname


Print user’s login name.


$ logname


smallfoot


ls


List directory contents.


$ ls


copy_of_lorem.txt  lorem.txt  moo.txt  www


man


Opens the manual page for a software or function.


$ man bash


md5sum


Outputs the MD5 hash sum of a file.


$ md5sum lorem.txt


56da9e37259af34345895883e6fd1a27  lorem.txt


mkdir


Makes a directory.


$ mkdir foobar


mv


Moves a file.


$ mv lorem.txt ipsum.txt


nl


Number lines of files.


$ nl lorem.txt


     1  Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod

     2  tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim

     3  veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea

     4  commodo consequat. Duis aute irure dolor in reprehenderit in voluptate

     5  velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint

     6  occaecat cupidatat non proident, sunt in culpa qui officia deserunt

     7  mollit anim id est laborum.


nm


List symbols from object files.


$ nm hello_world


080494a0 D _DYNAMIC

0804956c D _GLOBAL_OFFSET_TABLE_

08048474 R _IO_stdin_used

         w _Jv_RegisterClasses

08049490 d __CTOR_END__

0804948c d __CTOR_LIST__

08049498 d __DTOR_END__


od


Dump files in octal and other formats.


$ od -t x /bin/sh


2376640 00098020 000054d4 00000000 00000000

2376660 00000020 00000000 000000c7 00000008

2376700 00000003 080e6500 0009d4f4 00004ae8


pidof


Find the process ID of a running program.


$ pidof fetchmail


22392


ping


Pings a host.


$ ping -c 2 127.0.0.1


PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.

64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.048 ms

64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0.052 ms


— 127.0.0.1 ping statistics —

2 packets transmitted, 2 received, 0% packet loss, time 999ms

rtt min/avg/max/mdev = 0.048/0.050/0.052/0.002 ms


ps


Outputs running processes.


$ ps


  PID TTY          TIME CMD

21542 pts/12   00:00:00 bash

27706 pts/12   00:00:00 ps


pstree


Display a tree of processes.


$ pstree


init-+-2*[BitchX]

     |-3*[bash—sleep]

     |-fetchmail

     |-screen-+-bash—irssi

     |        `-bash—ctorrent

     |-screen-+-bash—lisp.run

     |        |-bash—vi

     |        |-2*[bash]

     |        `-bash—lynx

     |-2*[screen—bash—irssi]

     |-screen—irssi

     |-screen—bash

     |-screen-+-bash

     |        `-irssi

     |-skjerm—irssi

     |-sshd-+-5*[sshd—sshd—bash—irssi]

     |      |-8*[sshd—sshd—bash]

     |      |-sshd—sshd—bash—screen

     |      |-sshd—sshd

     |      `-sshd—sshd—bash—pstree

     `-syslog-ng


pwd


Outputs the name of current working directory.


$ pwd


/home/smallfoot


rm


Removes a file or directory.


$ rm lorem.txt


rmdir


Removes a directory.


$ rmdir foobar


sed


Stream editor for filtering and transforming text.


$ echo “My cat’s name is Bob” | sed -e ’s/Bob/Mittens/g’


My cat’s name is Mittens


sha1sum


Outputs the SHA1 hash sum of a file.


$ sha1sum lorem.txt


c942ddebd142ec8bacac9213d48096e74bab4957  lorem.txt


shutdown


Bring the system down in a secure way. All logged-in users are notified that the system is going down.


$ shutdown now


size


List section sizes and total size.


$ size /bin/bash


   text    data     bss     dec     hex filename

 621233   22712   19176  663121   a1e51 /bin/bash


stat


Outputs file status.


$ stat lorem.txt


  File: `lorem.txt’

  Size: 453             Blocks: 8          IO Block: 4096   regular file

Device: 77h/119d        Inode: 27312217    Links: 1

Access: (0644/-rw-r–r–)  Uid: ( 1478/smallfoot)   Gid: (  100/   users)

Access: 2007-03-03 12:24:39.000000000 +0000

Modify: 2007-03-03 12:24:39.000000000 +0000

Change: 2007-03-03 12:24:39.000000000 +0000


strings


Print the strings of printable characters in files.


$ strings hello_world


/lib/ld-linux.so.2

_Jv_RegisterClasses

__gmon_start__

libc.so.6

puts

_IO_stdin_used

__libc_start_main

GLIBC_2.0

PTRh%

[^_]

Hello World!


tail


Output the last part of files.


$ tail -2 lorem.txt


occaecat cupidatat non proident, sunt in culpa qui officia deserunt

mollit anim id est laborum.


talk


Talk to another user.


$ talk bob Lookout for the dopefish!


touch


Change a file’s access and modification timestamps. If file does not exist, create it.


$ touch lorem.txt


tty


Outputs the name of the current terminal.


$ tty


/dev/pts/16


uname


Outputs operating system, hostname, kernel version, date and timp, and processor.


$ uname -a


Linux anapnea.net 2.6.9 #1 SMP Wed Jul 19 16:24:18 MSD 2006 i686 Intel(R) Xeon(TM) CPU 2.80GHz GenuineIntel GNU/Linux


uptime


Outputs the system uptime.


$ uptime


 14:50:26 up 7 days, 17:52, 18 users,  load average: 0.08, 0.02, 0.01


users


Print the user names of users currently logged in to the current host.


$ users


alice bob charlie eve


vdir


List directory contents.


$ vdir


total 8

-rw-r–r– 1 smallfoot users 453 Mar  3 12:32 copy_of_lorem.txt

-rw-r–r– 1 smallfoot users 453 Mar  3 12:24 lorem.txt

-rw-r–r– 1 smallfoot users   0 Mar  3 12:32 moo.txt

lrwxr-xr-x 1 root      root   18 Feb 27 19:33 www -> /var/www/smallfoot


w


Show who is logged on and what they are doing.


$ w


 12:14:30 up 5 days, 15:16, 19 users,  load average: 0.00, 0.00, 0.00

USER     TTY        LOGIN@   IDLE   JCPU   PCPU WHAT

charlie  pts/0     Fri21    3:26m  2.52s  2.52s irssi

alice    pts/2     Wed17   30:21m  0.00s  0.00s -bash

emma     pts/4     11:37   36:57   0.00s  0.00s -bash

frank    pts/5     11:48   11:03   0.00s  0.00s -bash

smallfoo pts/12    12:01    0.00s  0.04s  0.01s w


wall


Send a message to everybody’s terminal.


$ wall next week we change the server for a new one


wc


Counts lines in a file.


$ wc -l lorem.txt


7 lorem.txt


whatis


Search the whatis database for complete words.


$ whatis bash


bash                 (1)  – GNU Bourne-Again SHell

bash [builtins]      (1)  – bash built-in commands, see bash(1)


who


Outputs who is currently logged into the system.


$ who


charlie  pts/0        Mar  2 21:37 (xtreme-11-65.acme.com)

alice    pts/2        Feb 28 17:48 (147.21.16.3)

emma     pts/4        Mar  3 11:37 (32.84-48-181.uac.com)

frank    pts/5        Mar  3 11:48 (port-212-202-233-2.foobar.org)

smallfoot pts/12       Mar  3 12:01 (c-12776f4.cust.example.net)


whereis


Locate the binary, source, and manual page files for a command.


$ whereis bash


bash: /bin/bash /etc/bash /usr/share/man/man1/bash.1.gz


whoami


Outputs your username / the name of your account.


$ whoami


smallfoot

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"Useful Commands For The Linux Command Line"

One thought on “"Useful Commands For The Linux Command Line"

  1. Dodie Holroyd says:

    Thanks a bunch for the magnificent article. I really like the site and thought which I’d let you know! 😀 Hi and thanks, Dodie Holroyd

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