Basic Linux Commands

Basic Linux  Commands

>> To check the present working directory

 [root@database ~]# pwd
/root

>> To show the contents of a directory (folder)

[root@database ~]# ls
3145.zip  args1    database_notes  Documents   ifcfg-eth1_March25  linux_image.iso  names         phonenubers  uln_migrate             uln_register.tar
args      BegPerl  Desktop         hello2.plx  index.html.1        mbox             oradiag_root  scripts   

>> To see more details including the permission regarding the contents of a directory (folder)

[[root@database ~]# ls -l
total 3511620
-rw-r--r--  1 root   root       422670 Dec 30 10:29 3145.zip
-rwxr--r--  1 root   root          105 Apr  8 21:45 args
-rwxr--r--  1 root   root           32 Apr  8 21:51 args1
drwxr-xr-x 17 root   root         4096 Dec 30 10:31 BegPerl
-rw-r--r--  1 root   root         5022 Jan  5 09:55 database_notes
drwxr-xr-x  3 root   root         4096 Mar 25 04:45 Desktop
drwx------  3 root   root         4096 Mar 30 21:33 Documents

>> To see all contents including hidden files of a directory (folder)

[root@database ~]# ls -a
.              .bashrc         .eggcups         .gstreamer-0.10     mbox                 scripts                 uln_register.tar             .xauthgXJKsS
..             BegPerl         .elinks          .gtkrc-1.2-gnome2   .metacity            .sqldeveloper           .vboxclient-clipboard.pid    .xauthixsRh6


>> To see tree structure of nested directories

[root@database ~]# ls -R /opt
/opt:
ORCLfmap
sqldeveloper
sun
VBoxGuestAdditions-4.2.6

/opt/ORCLfmap:
prot1_32

/opt/ORCLfmap/prot1_32:
bin
etc
log

/opt/ORCLfmap/prot1_32/bin:
Fmputl

>> To see a file starting from f

[root@database ~]# ls f*

>> To see a file have a middle string as disk

[root@database ~]# ls /bin/*disk*

>> To see a file whose length is 3 charaters

[root@database ~]# ls ???

>> To see a file which starts with single char & ends up with any number of character

[root@database ~]# ls ?edh*

>> To create a file
[root@database ~]# cat > file1

>>  To see file content
[root@database ~]# cat file1


>> To append a file

[root@database ~]  cat >> file1

[root@database ~] cat file1 file2 >> file3 #redirecting output to file3

[root@database ~] cat file3

>>  To create a file using touch command

[root@database ~]# touch f1 f2 f3 f4

[root@database ~]# ls

>>  Creating a single directory

[root@database ~]# mkdir dir

>> Creating multiple directories

[root@database ~]# mkdir dir1 dir2 dir3 dir4

[root@database ~]# ls

anaconda-ks.cfg  dir   dir2  dir4  f2  f4     file2  install.log     
labmanual
Desktop          dir1  dir3  f1    f3  file1  file3  install.log.syslog

>>  To create nested directories

[root@database ~]# mkdir -p d1/d2/d3/d4

>> To see the tree structure

[root@database ~]# ls -R d1
d1:
d2

d1/d2:
d3

d1/d2/d3:
d4

d1/d2/d3/d4:

>> To change a directory

[root@database ~]# cd dir1

[root@database ~]# cd ..

[root@database ~]# cd ../..

[root@database ~]# cd -
/root

[root@database ~]# pwd
/root

[root@database ~]# cd

[root@database ~]# pwd
/root

[root@database ~]#

13. To remove files

[root@database ~]# rm file1

rm: remove regular file `file1'? y

14. To remove an empty directory

[root@database ~]# rmdir dir1

[root@database ~]# ls
anaconda-ks.cfg  Desktop  dir2  dir4  f2  f4     file3        install.log.syslog
d1               dir      dir3  f1    f3  file2  install.log  labmanual

15. To remove a directory
[root@database ~]# rm -rf dir

[root@database ~]# ls
anaconda-ks.cfg  Desktop  dir3  f1  f3  file2  install.log         labmanual
d1               dir2     dir4  f2  f4  file3  install.log.syslog

To copy files

[root@database ~]# cp anaconda-ks.cfg file1

To copy folders

[root@database ~]# cp -r dir2 Desktop

To rename  directories and files

[root@database ~]# mv dir3 d4


[root@database ~]# ls
anaconda-ks.cfg  d4       dir2  f1  f3  file1  file3        install.log.syslog
d1               Desktop  dir4  f2  f4  file2  install.log  labmanual

To move directories and files

[root@database ~]# mv dir2 /opt

[root@database ~]# ls
anaconda-ks.cfg  d4       dir4  f2  f4     file2  install.log         labmanual
d1               Desktop  f1    f3  file1  file3  install.log.syslog


[root@database ~]# cd /opt

[root@database ~]#  ls
dir2

To search a word from single or multiple file’s

[root@database ~]# grep tom  /etc/passwd /etc/group /etc/gshadow

/etc/passwd:tom:x:500:500::/home/tom:/bin/bash
/etc/group:tom:x:500:
/etc/gshadow:tom:!::

[root@database ~]# cat /etc/passwd | grep tom

To see the type of file

[root@database ~]# file *

To view the date

[root@database ~]# date

[root@database ~]# date -s "07/15/2008 00:06:00 "
 mm/dd/yyyy hh:mm:ss
Tue Jul 15 00:06:00 EDT 2008

[root@database ~]# cal

[root@database ~]# cal 12 2008

[root@database ~]# man mkdir

[root@database ~]# man cal

To see the content screen wise

[root@database ~]# ls -l /bin  | less


Visual Interface (VI)


Commands to Go into Insert mode

To open a file use vi

e.g.
# vi test.txt

i   -  inserts the text at current cursor position
I   -  inserts the text at  beginning of line
a   -  appends the text after current cursor position
A   -  appends the text at end of line
o   -  inserts a line below current cursor position
O   -  inserts a line above current cursor position
r   -  replace a single char at current cursor position

Commands at execute mode

:q -  quit without saving
:q!   -  quit forcefully without saving
:w   -  save
:wq   -  save & quit
:wq! -  save & quit  forcefully
:x -  save & quit
:sh -  Provides temporary shell
:se nu -  Setting line numbers
:se nonu -  Removing line numbers
:84   -  Press enter goes to line 84

>> To move the cursor, press the h,j,k,l keys as indicated.   
             ^
             k              Hint:  The h key is at the left and moves left.
       < h       l >               The l key is at the right and moves right.
             j                     The j key looks like a down arrow
             v

w forward   word to word
b     back side word to word

>> Command's at command mode

dd   -  Deletes a line
2dd   -  Deletes 2 lines
yy   -  Copy a line
2yy   -  Copies 2 lines
p -  put  (deleted or copied text)
u -  Undo (can undo 1000 times)
Ctrl+r -  Redo
G - Moves cursor to last line of file
5G - Moves cursor to 5th line of file
Shift+ZZ -  save & quit
/ -  locate word


>> To find and replace words
:1,$s///gc

e.g.
:1,$s/world/universe/gc

1-- To start the search at from 1st line
$ -> End of File
s -> substitute
g -> global
c -> confirmation

>> To power off machine

# poweroff