Table of Contents

This is part 1 of the series Linux Command Line Interface.

Introduction

Command Line or Shell or bash refers to the same. Bash stands for ‘Bourne Again Shell’. Shell is an intermediate program which translates and transmits the keyboard commands to the operating system so that it can understand.

Open terminal emulator to access shell program. To open Terminal emulator, press Alt+F2. In the field shown, type the command gnome-terminal if you are using GNOME desktop environment or type konsole if you are using KDE desktop environment and then press Enter. Something like the following appears in the emulator window.

This is called shell prompt. Whenever it appears, the shell is ready to take commands. Here me is the username of computer user and linux is the computer name. Together [email protected]. Format may be little bit different for some linux distributions. If you see ‘#’ instead of ‘$’ as last character in command prompt, then the user has root or super user privileges. In some Linux distributions root account locked by default.

Let’s enter some simple commands to get used to shell.

Shell - CLI Interpreter
Shell - CLI Interpreter

Simple Linux Commands

date - Displays current day, date and time. Enter the command date and press Enter. Following result will display on command line.

[email protected] ~ $ date
Tue Sep 30 11:42:04 EDT 2014

clear - clears the terminal window. Type clear in terminal window and press Enter.

cal - Displays calender. Enter the cal command in terminal and press Enter.

[email protected] ~ $ cal
   September 2014     
Su Mo Tu We Th Fr Sa  
    1  2  3  4  5  6  
 7  8  9 10 11 12 13  
14 15 16 17 18 19 20  
21 22 23 24 25 26 27  
28 29 30

df - Displays amount of free space (in KB) on your disk drives. In the following information /dev/sda5 is the disk drive and out of 16492404 kilo bytes (~15.72 GB), 10034044 kilo bytes (~9.56 GB) are used. Total 65% of space is consumed.

[email protected] ~ $ df
Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/sda5       16492404 10034044   5597536  65% /
none                   4        0         4   0% /sys/fs/cgroup
udev             1274356        4   1274352   1% /dev
tmpfs             257452     1164    256288   1% /run
none                5120        0      5120   0% /run/lock
none             1287252      676   1286576   1% /run/shm
none              102400       16    102384   1% /run/user

free - Displays free memory (RAM in KB). Out of 2 and a half GB of RAM, 470MB is used in the following.

[email protected] ~ $ free
             total       used       free     shared    buffers     cached
Mem:       2574508     482048    2092460          0      54944     269392
-/+ buffers/cache:     157712    2416796
Swap:      2610172          0    2610172

lscpu - Displays CPU/Hardware information. Below shows a system with Intel i686 32 bit dual core (2 CPUs) processor.

[email protected] ~ $ lscpu
Architecture:          i686
CPU op-mode(s):        32-bit
Byte Order:            Little Endian
CPU(s):                2
On-line CPU(s) list:   0,1
Thread(s) per core:    1
Core(s) per socket:    2
Socket(s):             1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 14
Stepping:              8
CPU MHz:               1000.000
BogoMIPS:              3325.23
L1d cache:             32K
L1i cache:             32K
L2 cache:              2048K

exit - Exits the terminal emulator.