The document introduces Bash shell scripting, covering topics like shell operation, commands, environment variables, and scripting structures such as loops and conditionals. It also discusses tools like awk, grep, and sed, alongside practical examples and useful commands. Additionally, it provides guidance on getting started with GNU/Linux and automating tasks through scripts.

1. Shell Automation
An Introduction to
Bash Shell Scripting
Anoop John

2. An Outline
►Shell, interpreter, POSIX
►Shell script operation
►Commands, paths, returns
►Variables, environments
►Input, output, pipes, descriptors
►Expressions, conditions, loops
►Awk, grep, sed, find, xargs
►System utils
►Examples

3. Shell, Interpreter, POSIX
►Kernel, Shell
►Interprets commands
►Command Line Interpreter / Command Line
Interface
►POSIX compliance
►Sh, Bourne Again, Brian Fox, FSF

4. Free Software
►Unix
►GNU
►GPL - Four freedoms
►Use, Modify, Distribute, Modify &
Redistribute
►FSF
►GNU / Linux

5. Shell Operation
►Reads input from file, string (-c), or terminal
►Breaks the input into words and operators
►Parses the tokens into simple and compound
commands
►Performs the various shell expansions
►Performs any necessary redirections
►Executes the command
►Optionally waits for the command to complete
and collects its exit status

6. Commands
►Executables (ls)
►Shell commands (cd, exit, pwd)
►Return values
►Command input
►Command output
►Path
►Which

7. Variables & Environment
►Setting a Variable
►Environment (context)
►Script
►Eval
►Exec
►Source .
►Strings, integers, arrays
►Quoting - single, double, escaping
►Global, local

8. Shell Script
#!/bin/bash
echo “Hello World”;
name=Anoop
echo “Hello $name”
exit;

9. Arguments & Functions
►Shell Scripts
►Shell Arguments
►Functions
►Function Arguments

10. Shell Function
function log {
if [ $# ­gt 0 ]; then
echo "[$(date +"%D %T")] $@" >> $LOG_FILE
db "$@"
else
while read data
do
echo "[$(date +"%D %T")] $data" >>
$LOG_FILE
db "$data"
done
fi
}
log “Hello World!”
echo “Hello World!” | log

11. Input & Output
►Stdin
►Stdout
►Pipes
►Descriptors

12. Expressions
►Assignment =
►Arithmetic +, -, *, /, **,
►Bitwise <<, >>, |, &, ~, ^
►Logical !, &&, ||
►Comparisons - Arithmetic -eq, -ne, -lt, -gt, le
►Comparisons - String =, !=, <, >, <=
►Filesystem - -e, -f, -d, -x

13. If Command
if [[ expression ]] then
commands;
elif [[ expression ]] then
commands;
else
commands;
fi

14. Case Command
case $ANIMAL in
horse | dog | cat)
echo ­n "four"
;;
man | kangaroo )
echo ­n "two"
;;
*)
echo ­n "an unknown number of"
;;
esac

15. For Loop
for NAME [in LIST ]; do
COMMANDS;
done
i=0
for filename in `ls`; do
i=$(( i + 1));
printf "%­5s ­ %sn" $i “$filename”;
done;
for name in Anoop John; do
echo “Hello ${name}”;
done;

16. While Loop
while [[ expression ]]; do
COMMANDS;
done
i=0; while [[ $i ­lt 10 ]]; do
echo Counting $i;
((i+=1));
done;
while read line
do
echo $line
done < path/to/file

17. Shell Swiss Army Knives
►awk
►sed
►grep
►find
►xargs
►cat, less, tail, head, watch

18. Useful Commands
►ps
►top
►kill
►dmesg
►curl, wget
►chown, chmod, chgrp
►uptime, top, nice, nohup

19. Getting help
►man
►help
►command --help
►Reading scripts
►Mailing lists
►User groups
►Local community
►Search the web

20. How to Start
►Get GNU / Linux installed on your systems
►Start using shell
►Identify pain points in your daily operations
►Automate through scripts
►Join a mailing list
►Ask & answer questions
►Show off :-)

21. Exempli Gratia
►Drupal Backups
►Asianet Autologin
►Reliance Autologin
►Secure Shared Folders

22. About Zyxware
►Free Software Company
►Software Development - Drupal
►Leading Drupal Contributor from India
►FSF Contributing Member
►Free Software Support in the local market
►IT Training and FOSS Enabling
►Websites & Email Services
►IT Consultancy for Enterprises

23. Thank You!
www.zyxware.com
info@zyxware.com
9446-06-9446