A workshop on "An introduction to BASH shell scripting". Conducted at CSI Students Convention at TKM College of Engineering, Kollam, Kerala on 15th September, 2012 http://www.zyxware.com/articles/3080/zyxware-conducts-workshop-on-bash-scripting-at-tkm-college-of-engineering-kollam

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