Linux-More commands

To show the full path of shell commands found in your path

which <command name>
eg: which grep  
//output like: /bin/grep  

To locate the program, source code, and manual page for a command

whereis <command name>

To search for files anywhere on the file system

locate <keyword to search>
    //find all files and directories that contain the keyword

To search for files matching certain patterns

find <directory name> <pattern to search>
           eg: find . -name \*mp3
           // starts searching in the current directory “.” and all subdirectories, 
           // looking for files with “mp3” at the end of their names

To list currently running process


To list all process in the system

ps -aux  

To show who is logged on and what they are doing


To view the name of current user


To view the user details


To view host name


To set host name

hostname -a <new host name>

To print your user-id and group id’s


To get report on file system disk space usage


(In MB)

df -h  

To view disk usage in a particular directory


To view summary

du -s  

(In MB)

du -h  

To display CPU processes in a full-screen GUI

// type “Q” to quit  

To display amount of free and used memory in the system


To display information about your CPU

cat /proc/cpuinfo  

To display lots of information about current memory usage

cat /proc/meminfo  

To print system information to the screen

uname -a  

To print kernel version

uname -r  

To display the size of a file

wc -l  

(In bytes)

wc -m  

(In char)

wc -c  

(In word count)

wc -w  

To change permission to a file/directory

 chmod [-R] <permissions> <file name/directory name>
       eg: chmod 754 one.txt
       eg: chmod -R 777 /home/songs/
     read r=4; write w=2; execute x=1
     Owner      Group     Others
     rwx        r-x       r--
     7          5         4

To change ownership of a file/directory

chown [-R] <user name> <file name/directory name>
       eg: chown dhanoop one.txt
       eg: chown -R dhanoop /home/songs/

To search a file for a particular pattern

grep [-R] <word to search> <file name/directory name>
           eg: grep science science.txt
                //case-sensitive search
           eg: grep -i science science.txt
                //case-insensitive search
           eg: grep -i ‘spinning top’ science.txt
                //multiword search
           eg: grep -R passwd /etc/
                //search in directory

To clear the screen


To display text on screen

echo “<text to display>”
       eg: echo “Hello”

To print a file or program output

lpr <file name>
       eg: lpr mp3files.txt
<command> | lpr
       eg: ls -la | lpr

To sort a file or program output

    eg: sort mp3files.txt  

To switch user

su <user name>
   //to switch to a particular user account
   //to switch to root account
su -
   //to switch to root, and log in with root's environment

To give an alias name to a command for ease of use

alias <name>=”<command>”
    eg: alias list=”ls -l”

To display last logins of user


To display the name of currently working terminal


To block a user

passwd -l <user name>

To unblock a user

passwd -u <user name>

To add a user account

useradd [options] <username>

With specified home directory

useradd -d <home directory> <user name>

With specified shell

useradd -s <shell> <user name>

With specified initial group

useradd -g <initial group> <user name>

With specified expiry date

useradd -e <YYYY-MM-DD> <user name>

To lock/unlock a user account

usermod [-L or -U] <user name>

To delete a user account

userdel [-r] <user name>

To restart the system

shutdown -r now
            //without delay

To turn off the system


To reboot the system


To halt the system


To mount a file system or media

mount <source> <destination>
      eg: mount /dev/sda1 /mnt
            //mounting first partition of first SATA hard disk
      eg: mount /dev/hdb3 /mnt
            //mounting third partition of second hard disk

To umount a file system or media

umount <file system/media>
      eg: umount /mnt

To view IP address


To edit IP address temporarily

ifconfig -a etho <ipaddress>

To view partitions and file systems

fdisk -l  
    //view line by line  

To print selected columns in a file

cut -c <column range> <file name>
      eg: cut -c 3-5 sem.txt

To print particular fields

awk '{ print $<field number> }' <file name>
      eg: awk '{ print $2 }' sem.txt
            //prints second field
      eg: awk '{ print $1 $3 }' sem.txt
            //prints first and third fields

To know the shell

echo $SHELL
      //the symbol “$” precedes every user or system variable.
      //All system variables are BLOCK lettered.

To know the home directory

echo $HOME  

To print the calendar

      //prints calendar of current month
cal <YYYY>
      eg: cal 2010
      //prints calendar of specified year

To print the date


To temporarily switch to root to execute a single command

sudo <command>
    eg: sudo ifconfig -a eth0

To run an executable file

sh <file name>
      eg: sh new\ file
            // '\ ' denotes white space
./<file name>
      eg: ./new\ file

To view command history


To re execute last command


To execute nth command in history

    eg: !44
    // executes 44th command in the history  

To re execute last command that starts with specified character

    eg: !s
    // executes the last command that starts with letter “s”

To repeat the last command changing old character to new character

    eg: ^l^m
        // let 'wc -l' be the last command
        // so now 'wc -m' will be executed

Signals to a process

To list all signals

kill -l  

To kill a process

kill <process id>

To terminate a process

kill -9 <process id>

To normally exit a process

kill -15 <process id>

To login remotely to a system

ssh [<user name>@]<ip address>
      eg: ssh dhanoopbhaskar@

To execute a command on remote system through remote login

ssh [<user name>@]<ip address> <command>
    eg: ssh dhanoopbhaskar@ df -h
    //executing 'df -h' remotely

To copy file from a remote system

scp [-r] <source> <destination>
    eg: scp /home/a.c dhanoopbhaskar@