Intended for Centos or Redhat.
General
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.
Files
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
pwd
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 \;
Terminal
Bash Shell
clear the command screen
clear
Change user to root, the password will be asked
su root
Open a new subshell environment
bash
Show all variables and value of the environment
env
to quit the root session, or quit the terminal
exit
Create a variable in the environment and export it to all subshell
VARIABLE = "test"
export VARIABLE
The variable SHELL will tell you which shell you are currently using
echo $SHELL
Directories
Delete a directory
rm dir path/to/directory
C Shell
Change the shell from bash to the C Shell
csh
Show all variables and value of an environment
setenv
Set a value and show it
setenv VARIABLE "test"
echo $VARIABLE
TTY - teletype writer
show who is connected on the computer and on which session
who
Give which user you are
whoami
Console per default, with graphical environment
tty1
Use ctrl + alt + f2 to go to tty2 session. Use ctrl + alt + f3 to go to tty3 session, and so on.