Basic linux commands

Commands

useful link

 

1.  pwd – print working directory,In Unix-like and some other operating systems, the pwd command (print working directory) is used to output the path of the current working directory.

[root@nfsserver ~]# cd /var/log
[root@nfsserver log]# pwd
/var/log

2.  date – date command is used to display or eddit the current date and time of the  system.

[root@nfsserver log]# date
Wed Jun 10 02:27:59 EDT 2015

3.   who or w –  displays who is logged on to  Linux or Unix-like operating system using shell prompt. w command also show who is doing what.

[root@nfsserver log]# who
root     tty1         2015-05-21 22:51
root     pts/0        2015-06-10 02:13 (192.168.2.6)
hareram  pts/1        2015-06-10 02:36 (192.168.2.6)
hareshyam pts/2        2015-06-10 02:37 (192.168.2.6)

[root@nfsserver log]# w
 02:37:54 up 1 day,  4:09,  4 users,  load average: 0.00, 0.00, 0.00
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT
root     tty1     -                21May15  4:44m  0.50s  0.50s -bash
root     pts/0    192.168.2.6      02:13    0.00s  0.03s  0.00s w
hareram  pts/1    192.168.2.6      02:36   45.00s  0.00s  0.00s -bash
hareshya pts/2    192.168.2.6      02:37    8.00s  0.00s  0.00s -bash

 

4. whoami  – The whoami command writes the user name (i.e., login name) of the owner of the current login session to standard output.

[hareram@nfsserver ~]$ whoami
hareram
[hareram@nfsserver ~]$ id -un
hareram

5. man –  Command to display manual pages of Unix commands.

[root@nfsserver ~]# man head
Formatting page, please wait...
HEAD(1)                          User Commands                         HEAD(1)

NAME
       head - output the first part of files

SYNOPSIS
       head [OPTION]... [FILE]...

DESCRIPTION
       Print  the  first  10 lines of each FILE to standard output.  With more
       than one FILE, precede each with a header giving the file  name.   With
       no FILE, or when FILE is -, read standard input.

       Mandatory  arguments  to  long  options are mandatory for short options
       too.

       -c, --bytes=[-]K
              print the first K bytes of each  file;  with  the  leading  ‘-’,
              print all but the last K bytes of each file

       -n, --lines=[-]K
              print  the first K lines instead of the first 10; with the lead-
              ing ‘-’, print all but the last K lines of each file

5. info – Info is similar to man, with a more robust structure for linking pages together. Info pages are made using the texinfo tools, and can link with other pages, create menus and ease navigation in general.

5. –help –  shows help page for the given command

[root@nfsserver ~]# head --help
Usage: head [OPTION]... [FILE]...
Print the first 10 lines of each FILE to standard output.
With more than one FILE, precede each with a header giving the file name.
With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.
  -c, --bytes=[-]K         print the first K bytes of each file;
                             with the leading -', print all but the last
                             K bytes of each file
  -n, --lines=[-]K         print the first K lines instead of the first 10;
                             with the leading -', print all but the last
                             K lines of each file
  -q, --quiet, --silent    never print headers giving file names
  -v, --verbose            always print headers giving file names
      --help     display this help and exit
      --version  output version information and exit

6. head –    Command to display the first “n” lines in a file

[root@nfsserver ~]# head -n8 test1
a
b
c
d
e
f
g
h

7. tail – Command to display the last “n” lines in a file

[root@nfsserver ~]# tail -n 8 test1
i
j
k
l
m
n
o
p

8. cd –   Change Directory is a basic command which is used to change your working directory from one to other.

9. mkdir  – create directory

9. rmdir  – removes empty directory.

[root@redhatclass linux]# rmdir test

10. cp  – cp command  is used to copy one or more files or directories from source to destination.

11. mv  – Linux mv command is used to move files and directories from one location to another. Apart from moving the files, it can also rename a file or directory.

12. ln  – There are two type of link:

  •  Softlink:
  • hardlink

13. rm  – remove files and directories

14. touch  – create an empty file and also update timestamp

15. echo  –

16. cat  –cat 1-The cat command (short for “concatenate “) is one of the most frequently used command in Linux/Unix, Apple Mac OS X operating systems. cat command allows us to create single or multiple files, view contain of file, concatenate files and redirect output in terminal or files.   Ways to write file with cat:

 

 cat > outfile.txt 
>Enter text 
>to save press ctrl-d
cat > outfile.txt <<EOF
>some text
>to save
>EOF
cat file2.txt> file1.txt
cat file1.txt  file2.txt  > file12.txt

NOTE: if you do not want to overwrite , but appendend the new content then use >> instead of >

 

 

17. vi  – text editor,

18. >

19. >>  –

20. read  –

21. wc –

22. sort  –

23. uniq  –

24. locate – very fast search command in linux

25. find  – slow but powerful search command in linux

26. grep  –

27. egrep  –

28. more – command to display file which allows forward scrolling.

29. less  – command to display file which allows backward and forward scrolling.

30. history  –

31.tree –   list contents of directories in a structure like format under Linux operating systems

[root@nfsserver ~]# tree -LCd 1 /
/
├── bijan
├── bin
├── boot
├── cbb
├── dev
├── dir1
├── etc
├── home
├── lib
├── lib64
├── lost+found
├── media
├── misc
├── mnt
├── net
├── nfsshare
├── opt
├── proc
├── rhel6
├── root
├── sbin
├── selinux
├── srv
├── sys
├── test
├── tmp
├── usr
└── var

-L 1 = show only one level

-C = show colours

-d = show only directory

32. whatis –

33. which –  to show path of a command

34. whereis  – find and locate the binary, source, and manual page files for a given command.

35. tar –  The tar command used to rip a collection of files and directories into highly compressed archive file commonly called tarball or tar, gzip and bzip inLinux.

[root@nfsserver ~]# pwd
/root
[root@nfsserver ~]# ls -l
-rw-------. 1 root root 1857 Oct 11 2014 anaconda-ks.cfg
drwxr-xr-x 2 root root 4096 Jun 11 13:36 class
drwxr-xr-x. 3 root root 4096 Jun 9 20:15 Desktop
drwxr-xr-x. 3 root root 4096 Oct 11 2014 Documents
drwxr-xr-x. 4 root root 4096 Dec 27 21:27 Downloads
-rw-r--r--. 1 root root 50712 Oct 11 2014 install.log
-rw-r--r--. 1 root root 10033 Oct 11 2014 install.log.syslog

 

compress the class directory in current directory

[root@nfsserver ~]# tar -cvzf archive.tar.gz class
class/
class/saroj
class/school
class/history
class/number
class/tutorial
class/ba
class/commands
class/b
class/bidur
class/fdkjfk
class/a
class/bijan
class/sudhir
class/aloodum
class/ab
class/bijan.orig

list the contents of archive.tar.gz

[root@nfsserver ~]# tar -tvzf archive.tar.gz
drwxr-xr-x root/root         0 2015-06-11 13:36 class/
-rw-r--r-- root/root       217 2015-06-10 18:55 class/saroj
-rw-r--r-- root/root        54 2015-06-09 20:44 class/school
-rw-r--r-- root/root     23312 2015-06-10 19:55 class/history
-rw-r--r-- root/root        16 2015-06-10 19:34 class/number
-rw-r--r-- root/root       217 2015-06-10 18:54 class/tutorial
-rw-r--r-- root/root        51 2015-06-10 19:11 class/ba
-rw-r--r-- root/root       217 2015-06-10 18:56 class/commands
-rw-r--r-- root/root        17 2015-06-10 19:09 class/b
-rw-r--r-- root/root        72 2015-06-10 19:33 class/bidur
-rw-r--r-- root/root       235 2015-06-10 18:58 class/fdkjfk
-rw-r--r-- root/root        17 2015-06-10 19:09 class/a
-rw-r--r-- root/root       168 2015-06-11 13:35 class/bijan
-rw-r--r-- root/root       235 2015-06-10 18:56 class/sudhir
-rw-r--r-- root/root       256 2015-06-10 19:01 class/aloodum
-rw-r--r-- root/root        51 2015-06-10 19:10 class/ab
-rw-r--r-- root/root         0 2015-06-11 13:36 class/bijan.orig

 

untar the archive.tar.gz  in /tmp folder

[root@nfsserver ~]# tar -xvzf archive.tar.gz -C /tmp
class/
class/saroj
class/school
class/history
class/number
class/tutorial
class/ba
class/commands
class/b
class/bidur
class/fdkjfk
class/a
class/bijan
class/sudhir
class/aloodum
class/ab
class/bijan.orig
[root@nfsserver ~]# cd /tmp
[root@nfsserver tmp]# ls
class  hello 
[root@nfsserver tmp]# ls class/
a  ab  aloodum  b  ba  bidur  bijan  bijan.orig  commands  fdkjfk  history  number  saroj  school  sudhir  tutorial

 

 

 

 

 

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