Tells about the shells and how to get started with shell programming.with a snapshot of a basic shell script.

1. Shell Scripting
Linux shell programming
02/26/13

2. Introduction
• A shell is a program constructed of shell commands
( $shell,$path,Ls,pwd,mkdir..)
• Shell is an environment for user interaction.But it is
not a part of kernel.
• Shell is just like as BAT files in MS-DOS.
• By default,Bash shell is default shell for Linux.
02/26/13

3. Features of Shells
• Shells are CASE SENSITIVE.
• Shells allows interaction with kernel.
• Shells allow one to create functions and pass
arguments to them.
• Shells provide help for each and every command
using man or help.
• Helps in automation of tasks and thus time saving
02/26/13

4. Types of shells
• Following types of shells are available in linux:
Shell Name Developer Promp Description
t
Bash – Brian Fox & $ Bash is the replacement
Bourne again Chet Ramey of sh shell.It provides
many tools for editing
and manipulating
history.
CSH - C shell Bill Joy % C shell has its syntax
much same as that of C
language.
Some other types of shells available are KSH Korn
shell,TCSH tenex/Tops C shell
02/26/13

5. Shell Scripting
• A script is defined as just a plain text file or ASCII
file
– with a set of linux / unix commands.
– Flow of control
– IO facilities
• A shell script can be created using any
text editor like vim,emac,notepad++ etc.
02/26/13

6. • Shell script allow use of variables.
• Shell scripts are interpreted directly and are not
compiled as cc++ codes.
• Shells provide many features including loop
constructs,arrays,variables,branches and functions.
• shells provide logic with other utilities like
pipelining,redirection etc.
• Shells allow file and directory management features.
02/26/13

7. Example of Shell scripting
02/26/13

8. Structure of a script
• #!/bin/bash –it defines that in which shell will be used
to run the script.
• # comments –comments can be made by using #
symbol in a script.
• Chmod +x script.sh – to tell the linux that file is
executable.
• ./script.sh to execute the script.
To check current shell ,type following:
echo $SHELL.
02/26/13

9. Advantages of shell scripting
• Shell script is much quicker
than programming in any
other languages.
• To automate the frequently
performed tasks.
• Easy to use and understand.
Non-geeks can also modify
scripts.
02/26/13

10. Disadvantages of shell scripting
• Slow execution speed.
• Prone to costly errors.
• Compatability problems
02/26/13

11. References
 Shell Scripting for Unix/Linux: Shell scripting
advantages and disadvantages
 Bash Shell Script Function Examples
 Linux Shell Scripting Tutorial - A Beginner's
handbook
 LinuxHelp.net
02/26/13

12. 02/26/13