Intended for Centos or Redhat.


Run commands as root

sudo -i

root is a super user, to use root use su (which can also be used to switch account, you need to know the password to the account you wish to use). Another option is to use sudo using your own password where you have been pre-approved to use root privilege.


Listing filename

List the file in the directory -l Give the file with information on rights, creator, size and creation date, and -R and to list all the subdirectories

ls -l -R

List the file in the directory that contain the word

ls *word*

list files that contains word1 or word2,

ls [word1,word2]*

can work for just a character

ls *word[12]*

look for file containing 2013, 2014, 2015

ls *{2013..2015}

Look for a file beginning with a letter between H to C, the second letter can be between A to Z, the third letter would be a number from 0 to 9, the last three character can be anything

ls [HC][A-Z][0-9]???

File Manipulation

Allows printing on the command the content of a file

cat file.txt

Create a file

touch file.txt

Using pipes in the command

Show and sort the file alphabetically the left column

cat file | sort

The same as before however grep is used to find words, and the “v” in grep suppress the line that contains “Word” or “last”

cat file | sort | grep -v "Word" | grep -v "last"

Input - output

store in a file the results of the command

ls -R > file.txt

add the result of the command to file.txt without erasing it

ls >> file.txt

grep look for the “word” of the input file.txt

grep -1 "word" < file.txt

Sort the element of the left side (default) from the input file.txt

sort < file.txt

save the results with file.txt as an input in filesorted.txt as an output

sort < file.txt > filesorted.txt 

Finding files

Using locate

Get file statistic on the system

locate -S

Tell you where the file exist, it is stored in the mlocate.db that is updated automatically

locate file

Search non case-sensitive file name location, i for the non-sensitive case, c to count the number of results

locate -ic file

Using Which

Get the location of binary executable, details about linux content

which ifconfig

Using find

Print working directory


will look for every directory that begin with “word” (the * does that)

find -name "word*"

Count the number of files in the current directory. The . is for the current directory, -type f is for a file, -print to print there name, wc -l will count the number of lines (1 line = 1 file).

find . -type f -print | wc -l 

Will show the files created in the directory in the last 3 minutes

find -cmin -3

Perform actions on files that are found Find files from a specific user -user username with a specific title -name that are bigger than 500 characters -size 500c then -exec will run Move to the result of the search to the /home folder with {} as the result, and \; to mark the end.

find -user username -name "file[0-9][0-9].txt" -size 500c -exec Move {} /home \;

Move files with -size bigger than 500 characters

find -type f  -exec mv {} /home/large \; 


Bash Shell

clear the command screen


Change user to root, the password will be asked

su root

Open a new subshell environment


Show all variables and value of the environment


to quit the root session, or quit the terminal


Create a variable in the environment and export it to all subshell

VARIABLE = "test"

The variable SHELL will tell you which shell you are currently using

echo $SHELL 


Delete a directory

rm dir path/to/directory

C Shell

Change the shell from bash to the C Shell


Show all variables and value of an environment


Set a value and show it

setenv VARIABLE "test"

TTY - teletype writer

show who is connected on the computer and on which session


Give which user you are


Console per default, with graphical environment


Use ctrl + alt + f2 to go to tty2 session. Use ctrl + alt + f3 to go to tty3 session, and so on.