1/29/11

Unix Miscellaneous commands

  1. ls
  2. pwd
  3. ln
  4. head
  5. tail
  6. cal
  7. ps
  8. kill
  9. who
  10. whoami
  11. uptime
  12. ut
ls : This command displays files and directories in columnar format.


Example:


$ ls


$ ls -S                

Aarrange the files based on the size(S is upper letter)


$ ls -l                

long listing the files


$ ls -a                

Displays hidden files


$ ls -i 

Displays inodes for each file


$ ls -R            

Displays all directories along with subdirectories in current working directory.


creating a hidden file:


$ cat >.employee.txt            


Wild card characters using with ls command.


 Represents single character
*   Represents gruop of characters
[  ]   Represents searching pattern


Examples:


$ ls ?                Displays files with one letter


$ ls x*               Displays files which are starting with 'x'


$ ls ???           Displays files with 3 letters


$ ls *.out          Displays all the files with extension 'out'


$ ls [a-z]           Displays single character files which are from a to z


$ ls [a-z]*          Displays files starting with a to z


$ rm ?               Removes the files with single character


$ rm *.c             Removes the files with extension 'c'


$ cp ? chennai       Single digit files will be copied into directory 'chennai'


pwd : This command shows current working directory in unix


$ pwd



head :  Used to display First lines of the file


Syntax:


$ head -n  filename


Example:


$ head  paypal.txt


     This command dispalys default 10 lines of the file paypal.txt


$ head -n15  paypal.txt


    This command displays 15 lines of the file paypal.txt


$ head -n3  paypal.txt


    This command displays 3 lines of the file paypal.txt


tail : Used to display last lines of the file.


Ex:


$ tail paypal.txt


      This command displays default last 9 lines.


$ tail -n5 paypal.txt


      This command displays last 4 lines of the file.


$ tail -n15 paypal.txt


       This command displays last 14 lines of the file.


cal command: Used for display the calender.


Syntax:


$ cal


$ cal  [Month No] [Year]


Ex:


$ cal 2011                Displays 2011 calender


$ cal  2   2011          Displays Feb month in 2011 year


ln :


1.This will create link between 2 files.(2nd file should new one)


2. If one file modified another one affected.


Ex:


$ln paypal.txt    funpal.txt


ps : Knowing backgroud process running /stopped


$ ps pid     


kill : Used for terminating the process


Ex:


$ kill  pid


who : Used for to display who are working in the system


Ex:

$ who

whoami: Display my user name/accout


Ex:


$ whoami


uptime: This command used for display load in the server.


$ uptime


ut: displays current unix time

advance_date : Used to time forward the unix server.

$ advance_date

reset_time.py : Used to reset time and date in unix server.

$ reset_time.py