case "$1" in

(runApp1)

runApp1

exit 1

;;

(runApp)

runApp

exit 0

;;

(*)

echo "Usage: $0 {runApp1|runApp}"

exit 2

;;

esac

++++++++++++++++++++++++++++++++++++++++++++++++++++++++

#!/bin/bash

# file.sh: a sample shell script to demonstrate the concept of Bash shell functions

# define usage function

usage(){

echo "Usage: $0 filename"

exit 1

}

# define is_file_exists function

# $f -> store argument passed to the script

is_file_exists(){

local f="$1"

[[ -f "$f" ]] && return 0 || return 1

}

# invoke usage

# call usage() function if filename not supplied

[[ $# -eq 0 ]] && usage

# Invoke is_file_exits

if ( is_file_exists "$1" )

then

echo "File found: $1"

else

echo "File not found: $1"

fi

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

#!/bin/bash

# ref-params.sh: Dereferencing a parameter passed to a function.

# (Complex Example)

ITERATIONS=3 # How many times to get input.

icount=1

my_read () {

# Called with my_read varname,

#+ outputs the previous value between brackets as the default value,

#+ then asks for a new value.

local local_var

echo -n "Enter a value "

eval 'echo -n "[$'$1'] "' # Previous value.

# eval echo -n "[\$$1] " # Easier to understand,

#+ but loses trailing space in user prompt.

read local_var

[ -n "$local_var" ] && eval $1=\$local_var

# "And-list": if "local_var" then set "$1" to its value.

}

echo

while [ "$icount" -le "$ITERATIONS" ]

do

my_read var

echo "Entry #$icount = $var"

let "icount += 1"

echo

done

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

#!/bin/bash

# Arabic number to Roman numeral conversion

# Range: 0 - 200

# It's crude, but it works.

# Extending the range and otherwise improving the script is left as an exercise.

# Usage: roman number-to-convert

LIMIT=200

E_ARG_ERR=65

E_OUT_OF_RANGE=66

if [ -z "$1" ]

then

echo "Usage: `basename $0` number-to-convert"

exit $E_ARG_ERR

fi

num=$1

if [ "$num" -gt $LIMIT ]

then

echo "Out of range!"

exit $E_OUT_OF_RANGE

fi

to_roman () # Must declare function before first call to it.

{

number=$1

factor=$2

rchar=$3

let "remainder = number - factor"

while [ "$remainder" -ge 0 ]

do

echo -n $rchar

let "number -= factor"

let "remainder = number - factor"

done

return $number

# Exercises:

# ---------

# 1) Explain how this function works.

# Hint: division by successive subtraction.

# 2) Extend to range of the function.

# Hint: use "echo" and command-substitution capture.

}

to_roman $num 100 C

num=$?

to_roman $num 90 LXXXX

num=$?

to_roman $num 50 L

num=$?

to_roman $num 40 XL

num=$?

to_roman $num 10 X

num=$?

to_roman $num 9 IX

num=$?

to_roman $num 5 V

num=$?

to_roman $num 4 IV

num=$?

to_roman $num 1 I

# Successive calls to conversion function!

# Is this really necessary??? Can it be simplified?

echo

exit

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

count_lines_in_etc_passwd()

{

[[ -r /etc/passwd ]] && REPLY=$(echo $(wc -l < /etc/passwd))

}

if count_lines_in_etc_passwd

then

echo "There are $REPLY lines in /etc/passwd."

else

echo "Cannot count lines in /etc/passwd."

fi

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

function lsext()

{

find . -type f -iname '*.'${1}'' -exec ls -l {} \; ;

}

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

$ function batchexec()

{

find . -type f -iname '*.'${1}'' -exec ${@:2} {} \; ;

}

$ cd ~

$ batchexec sh ls

$ batchexec sh chmod 755

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

$ function rpass() {

cat /dev/urandom | tr -cd '[:graph:]' | head -c ${1:-12}

}

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

$ function getip()

{

/sbin/ifconfig ${1:-eth0} | awk '/inet addr/ {print $2}' | awk -F: '{print $2}';

}

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

$ function mach()

{

echo -e "\nMachine information:" ; uname -a

echo -e "\nUsers logged on:" ; w -h

echo -e "\nCurrent date :" ; date

echo -e "\nMachine status :" ; uptime

echo -e "\nMemory status :" ; free

echo -e "\nFilesystem status :"; df -h

}

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

function ll ()

{

clear;

tput cup 0 0;

ls --color=auto -F --color=always -lhFrt;

tput cup 40 0;

}

$ type ll

ll is a function

ll ()

{

clear;

tput cup 0 0;

ls --color=auto -F --color=always -lhFrt;

tput cup 40 0;

alias ls="ls --color=auto -F"

}

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

find -mindepth 3 -maxdepth 5 -name passwd

find / -iname "passwd" -exec md5sum {} \;

find . -perm -g=r -type f -exec ls -l {} \;

find . -perm g=r -type f -exec ls -l {} \;

Finding the Top 5 Big Files

find . -type f -exec ls -s {} \; | sort -n -r | head -5

Finding the Top 5 Small Files

find . -type f -exec ls -s {} \; | sort -n | head -5

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Create Alias for Frequent Find Operations

If you find some thing as pretty useful, then you can make it as an alias. And execute it whenever you want.

Remove the files named a.out frequently.

# alias rmao="find . -iname a.out -exec rm {} \;"

# rmao

Remove the core files generated by c program.

# alias rmc="find . -iname core -exec rm {} \;"

# rmc

15. Remove big archive files using find command

The following command removes *.zip files that are over 100M.

# find / -type f -name *.zip -size +100M -exec rm -i {} \;"

Remove all *.tar file that are over 100M using the alias rm100m (Remove 100M). Use the similar concepts and create alias like rm1g, rm2g, rm5g to remove file size greater than 1G, 2G and 5G respectively.

# alias rm100m="find / -type f -name *.tar -size +100M -exec rm -i {} \;"

# alias rm1g="find / -type f -name *.tar -size +1G -exec rm -i {} \;"

# alias rm2g="find / -type f -name *.tar -size +2G -exec rm -i {} \;"

# alias rm5g="find / -type f -name *.tar -size +5G -exec rm -i {} \;"

# rm100m

# rm1g

# rm2g

# rm5g