Explore Linux Commands, Shell Scripting over a weekend

uname - print system information

This lecture covers the following commands,

arch - print machine hardware architecture name

hostid - prints numeric identifier of current host

hostname - print local host name

free - display amount free and used memory in the system

id - prints real and effective user id and group id

This lecture covers the following commands,

logname - prints the user's login name

whoami - prints the effect user id

users - prints the currently logged in users information

groups - print the groups that a user is in

who - show who is logged in

date - print or set the system date and time

cal - displays a calendar

This lecture cover the following commands,

printenv - print all or part of environment variables

echo - writes argument into standard output

cd - change the current working directory

mkdir - make directories

This lecture covers the following commands,

df - reports file system disk space usage

du - estimates the file space usage

This lecture covers the following commands.

which - shows full path of the command

whatis - displays one line manual page descriptions

This lecture covers the following commands,

whereis - locate the binary, source, and manual page files for a command

sum - checksum and count the blocks in a file

cksum - checksum and count the bytes in a file

md5sum - compute and check MD5 message digest

base64 - base64 encode/decode data and print to standard output

sha1sum - compute and check SHA1 message digest

sha256sum - compute and check SHA256 message digest

sha384sum - compute and check SHA384 message digest

sha512sum - compute and check SHA512 message digest

This lecture covers the following commands,

mkdir - make directories

rmdir - remove empty directories

rm - remove files or directories

This lecture covers the following commands,

rm - remove files or directories

reverse search of commands instead of typing in command terminal

cd - change the working directory

basename, dirname - strip directory and suffix from filenames

This lecture covers the following commands,

cp - copy files and directories

mv — move files

This lecture covers the following commands,

ln - make links between files

unlink - call the unlink function to remove the specified file

This lecture briefs the following commands,

stat, fstat, lstat, fstatat - get file status

od - dump files in octal and other formats

This lecture briefs the following commands,

cat - concatenate files and print on the standard output

tac - concatenate and print files in reverse

nl - number lines of files

This lecture briefs about the following commands,

head - output the first part of files

tail - output the last part of files

This lecture briefs the following commands,

more - file perusal filter for crt viewing

less - opposite of more

This lecture briefs the following commands,

grep — search a file for a pattern

This lecture briefs the following commands,

cut - remove sections from each line of files

This lecture briefs the following commands,

ps - report a snapshot of the current processes.

This lecture briefs the following commands,

pstree - display a tree of processes

uptime gives a one line display of the following information.

The current time, how long the system has been running, how many users are currently logged on, and the system load averages for the past 1, 5, and 15 minutes.

kill command can be used to send any signal to any process group or process.

nohup - run a command immune to hangups, with output to a non-tty

nice - run a program with modified scheduling priority

top - display Linux processes

pmap - report memory map of a process

slabtop - display kernel slab cache information in real time

tload - graphic representation of system load average

lsof - list open files

proc - process information pseudo-filesystem

procinfo - Shows System Statistics from /proc Filesystem

•Top level directory of file system

•Contains all required files to boot the linux before other filesystem mounted

•Includes all executables & libraries required to boot the system

•Once booted, mounts other filesystems on standard mount points

•mount points are sub directories of root file system

•Should general be small in size

•Should be infrequently modified filesystems, lesser the chance of corruption

• Command line interpreter of GNU/Linux Operating System

• Basically provides an environment to execute other programs

• Provides a command line interface to execute different commands

• Basically as shell user program, provides interface to OS services

• Shell scripts can be used to perform various operations like,

  • File manipulations

  • Program execution

  • Printing texts •

• Different Linux Shells

  • Bourne Shell, C Shell, GNU Borne Again Shell (BASH)

This lecture briefs about the following,

• Linux Shell Variable Definitions

• Valid & Invalid Shell variable definitions

• Accessing the value of shell variables

• readonly

• deleting / unset the variable

This lecture briefs about shell variable types like

• Local Variables

• Environment Variables

• Shell Variables

Syntax of array declaration is as given below,

• <array name> =(value1 …. valuen)

Accessing the array values

• ${array[index]}

Access all the values in the array can be done as below,

• ${array[*]}

• ${array[@]}

Operator Description

+ Adds value on either side of the operand

- Subtracts the right from left hand operand

* Multiplies either sides of the operand

/ Divides left hand by right hand operand

% Divides left hand by right hand & returns remainder

= Assigns left with right operand

== Compares two operand whether both are equal or not

!= Compares two operand whether both are not equal or no

• if … else are useful for decision making

• can be used to select option from the respective available options

• Shell script supports the following types,

  • if … fi statement

  • if … else … fi statement

  • if … elif … else … fi statement

-eq Checks whether two operands are equal or not

-ne Checks whether two operands are not equal or not

-gt Checks whether left is greater than right operand or not

-lt Checks whether left is lesser than right operand or not

-ge Checks whether left is greater than or equals to right operand or not

-le Checks whether left is lesser than or equals to right operand or no

! Logical Negation

-o Logical OR Operation

-a Logical AND operation

== Checks whether both strings are equal or not

!= Checks whether both strings are not equal or not

-z Checks whether the given string size is zero or not

-n Checks whether the given string is non-zero or not

-b Checks whether file is a block special file or not

-c Checks whether file is character special file or not

-d Checks whether file is directory or not

-f Checks whether file is an ordinary file or not

-r Checks whether file is readable or not

-w Checks whether file is writable or not

-x Checks whether file is executable or not

-e Checks whether file is present or not

The syntax of the while loop is as given below,

                      while [ <condition> ]

                      do

                                    …………….

                                    …………..

                      done

The syntax of for loop is as given below,

                            for var in word1 word2 …. wordN

                            do

                                   • …………….

                                   • …………..

                           done

The syntax of the until loop is as given below,

                      until [ <condition> ]

                      do

                                    …………….

                                    …………..

                      done

This lecture briefs about the basic environment setup for getting started with C Programming. Also this briefs the information about VIM Editor, GNU Compiler, GNU Debugger. This also presents the commands and editing, saving and playing with VIM editor.