Useful Unix OS Commands

I have listed some useful unix operating system level commands, if you are new and looking for the tutorials and stuff hope these commands will help in performing difference operations. Cheers and Good Luck!

grep
----
used to find a specific word

head
----
this command is used to read starting lines of a file

tail
----
this command is used to read the last lines of a file

nohup
-----
Command is used to run processes in background

gzip
----
this command zip files in unix

gzcat
-----
this command is used to view the zipped file

for
---
we use loops in a console or shell sctipts to execute any command more than once

cp
--
copy command

mv
--
move command

rm
--
it deletes file

rmdir
-----
remove directory

mkdir
------
creates directory

awk
-----
this command is string manupulation, and is major use is to print columns from a file and other sources

sed
----
stread line editor is also a string manupulation command used for manupulation data as per requirement

>
---
this is very important symbol which redirects an output to a file rather than displaying on consoele

>>
---
this redirection sign append data content in a file that alresdy contain data

find
-----
to locate or find a command from various directories or same directory we use this command

cat
----
to read only a file we use this command

ps -ef
-------
this command is used to find the running processes on the server

bash
-----
shell mostly used for shell scripting and on console as well

chmod
--------
to change the permisions

crontab
--------
this is a scheduler in unix where we schedule our jobs for execution on specified time, read it from internet also

Crontab syntax :
A crontab file has five fields for specifying day , date and time followed by the command to be run at that interval.

*     *     *   *    *        command to be executed
-     -     -   -    -
|     |     |   |    |
|     |     |   |    +----- day of week (0 - 6) (Sunday=0)
|     |          |   |
|     |     |   +------- month (1 - 12)
|     |          |
|     |     +--------- day of month (1 - 31)
|     |     
|     +----------- hour (0 - 23)
|
+------------- min (0 - 59)

df
---
shows free disk space

du
---
shows disk usage

prstat -a
----------
shows systems current status

vi
---
editor used in unix to create/update files

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Author:
Waqas Rafi