Basic Commands

RHEL Linux basic commands cat bzip gzip pwd cd mkdir

In our last assignment you perform some basic task related to system administration from normal user. In this assignment we will extend this further. To complete this assignment login form our normal user Vinita.

How to redirect the matter of files in a new file

Create two file and write some text in them.

$cat > one
This is first file
$cat > second
This is second file

Now we will combine these two files in a single file. In standard linux its call redirection of output.

$cat one second > new
$cat new
This is first file
This is second files

Then what exactly this command did? As you know cat command is used to display the matter of file so it will first display the matter of first file and then it will display the matter of second file. But as you put a > sign at the end of command so despite of showing this output on screen command will redirect this matter to a file.

How to execute multiple commands in a single row

$[command] ; [command] ; [command] ;[command]……..

To execute multiple commands from single row use a ; between them form example

$cat new ; mkdir xyz ; mkdir rat ; ls
This is first file
This is second files
new xyz rat

this command will first execute the first command which is cat new so it will display the matter of new file, further is mkdir xyz so it will create a xyz directory , further is mkdir rat so will create a rat directory and in the end we use ls command so it will list the contain of current directory.

How to create multiple sub directory form single command

To create multiple sub directory from a single command use –p switch with mkdir command for example

$mkdir –p a/b/c/d/f/g/h/i/j

In this example we created 9 subdirectories form a single mkdir command. Now verify it by listing.

$ls
new  xyz rat a

now change the directory to verify the depth of directories.

$cd a/b/c/d/f/g/h/i/j
$pwd
/home/vinita/a/b/c/d/f/g/h/i/j

Come back to home directory. Simple cd command without passing any argument will do this.

$cd

How to move multiple file in directory with a single commands?

Give all files name one by one with a single space between them and in the end give the destination directory name for example
$mv new first second xyz

This command will move three files new, one, second to the xyz directory.

$cd xyz
$ls
New one second
$cd ..

how to take back-up and restore files and directories.

tar command is used to take the back up with –cvf switches and the same tar command is used to restore the matter with –xvf switches. For example

$tar –cvf backup.tar xyz
$ls
$rm –rf xyz

In linux you cannot restore the data once deleted unless you have backup. Now restore these files and directory.

$tar –xvf backup.tar
$ls
$cd xyz
$ls
new first second
$cd ..

How to compress files to save disk space?

Create a large file and check how much disk space is consumed by this file

$man ls > manoj
$du –h manoj
12k manoj

File manoj is using 12k space on hard disk. For exam prospective you should familiar with two compress utilities.

$bzip2 [file name]                      {command syntax}
$bzip2 manoj
$ls
$du -h  manoj.bz2
4k manoj.bz2

To decompress file
$bzip2 –d manoj.bz2 $ls manoj as you can show file has been decompressed. Now use other utility to compress the file.

$gzip manoj
$ls
manoj.gz
$du –h manoj.gz
4k manoj.gz
$gzip –d manoj.gz
$ls
manoj