Unix Commands

                                                          Unix Commands


1)nohup scriptname & - Automatically runs the jobs in the background even after exit

2)disown -h jobID--runs the jobs even if you exit from the terminal
   disown -r  -deletes all the running jobs
   disown jobid -Removes specific running active job
   disown -a  --deletes or removes all the active jobs

3)exit or CTRL+D - exit from the terminal

4)ps aux           ... list the status of all jobs by process  identifier (PID)
   PS -A   --Process of All users
   PS -u Vivek --Process of  Single users

5) jobs -l -displays all the running and non running jobs

6)rm -rf foo/bar/baz-- removing the present directory
   rmdir name_of_directory--remove directories if empty
   rmdir -p foo/bar/baz--removing the present directory and its parent directories even if files exists
   rm filename - Contents are recoverble
   rm -Rf filename - Force remove -- contents are not recoverable

7)ls -l             ... list all files in the current working directory, along with each file's   permission, owner, size in bytes and date  of last modification.

8) ctrl  c           Abort the program currently running
    ctrl z           Suspend the program currently running (use  fg or bg to resume the program in the foreground or background, respectively)
 
9)KILL -15 <>--CLEANUP operations and Uses SIGTERM signal
 
10)KILL -9 <> -No CLEANUP operations and Uses SIGKILL signal
 
11)shred option filename -Overwriting the existing file multiple times and securely deleting the file

12)grep -a1 "fedora" sample.dat -- Print the serched line plus the above and below 1 lines
      grep -A1 "fedora" sample.dat-- Print the serched line plus above the serached pattern one line
      grep -B1 "fedora" sample.dat--Print the serched line plus  below the serached pattern one line

13)set number -sets the line number in the unix sh file.

14)ls -F --list filenames with a special character at the end that tells you what kind of file it is ("/" for directory, "*" for unix executable, "@" for alias/symlink, etc)

15) grep -n "search string" filename will display the serched string and the line number
For Ex:
1ABC
2ABC

16)Hard Link  -- ln filename pointerfilename--contains inode number of that file--Once deleted hardlink ,still the contents are visible
   New File is not created and the file is just a mirror of the original file. 
   Cannot be used across filesystems    ,Consumes extra space since new file
   with new inode number  is created.   
  
     Soft Link-- ln -s filename pointerfilename--contains  file name to reference the file--
    Once deleted softlink ,the contents are not visible
                            New File is not created and the file is just a mirror of the original file.
              Can be used across filesystems,does not consume extra space since new file with new inode number is not created.
http://www.maxi-pedia.com/difference+between+symbolic+link+and+hard+link

ls -il --To see the hard and soft links in the particular directory

ls -F--When Soft link is created , the filename ends with @symbol which can be seen and identified as softlink by using this command.