#!/bin/bash
# filename.sh : this is a do-nothing script
...
# bash code goes here
...

bash$ /bin/bash filename.sh

#!/usr/bin/perl -w
# filename.pl : this is a perl script
...
# perl code goes here
...

bash$ /usr/bin/perl -w filename.pl

bash$ which bash
/bin/bash

#!/usr/bin/env bash
# filename.sh : this is a do-nothing script
...
# bash code goes here
...

bash$ echo $PATH
/bin:/usr/bin:/sbin:/usr/sbin:/usr/X11R6/bin:.

#!/bin/bash
# hello.sh : this is a hello-world script
echo "hello world"

#!/bin/bash
# hello.sh : this is a hello-world script
str1="hello world"
echo "$str1"

#!/bin/bash
# hello.sh : this is another hello-world script
str1="hello world"
str2="hello world again"
echo -e "$str1\n$str2"

hello world
hello world again

str1="hello world"
echo '$str1'

#!/bin/bash
# hello.sh : this is a hello-world script
echo "hello `whoami`"
#echo "hello $(whoami)"

#!/bin/bash
# whereami.sh : this is a 'where am I' script
str1="`whoami`"
str2="`pwd`"
echo "$str1 is now viewing the \"$str2\" folder"

ahmad is now viewing the "/home/ahmad/my-scripts/" folder

#! /bin/bash
# rect-area.sh : a script to find area of rectangle
echo -n "Enter width: "
read width
echo -n "Enter height: "
read height
area=`expr $width '*' $height`
echo "Area of rectangle=${width}x${height}=$area"

bash$ ./rect-area.sh
Enter width: 15
Enter height: 3
Area of rectangle=15x3=45
bash$

# from BASH INFO
`ID++ ID--'
     variable post-increment and post-decrement
`++ID --ID'
     variable pre-increment and pre-decrement
`- +'
     unary minus and plus
`! ~'
     logical and bitwise negation
`**'
     exponentiation
`* / %'
     multiplication, division, remainder
`+ -'
     addition, subtraction
`<< >>'
     left and right bitwise shifts
`<= >= < >'
     comparison
`== !='
     equality and inequality
`&'
     bitwise AND
`^'
     bitwise exclusive OR
`|'
     bitwise OR
`&&'
     logical AND
`||'
     logical OR
`expr ? expr : expr'
     conditional evaluation
`= *= /= %= += -= <<= >>= &= ^= |='
     assignment
`expr1 , expr2'
     comma

#!/bin/bash
# fact.sh factroize an integer to primes
echo -n "Enter an integer: "
read n
echo "$n[p]s2[lip/dli%0=1dvsr]s12sid2%0=13sidvsr\
[dli%0=1lrli2+dsi!>.]ds.xd1<2" | dc

bash$ grep -e vfat /etc/fstab >/dev/null; echo $?
0

bash$ grep -e vfat /etc/fstab >/dev/null &&
>	echo "yorika! I found It." || 
>	echo "good luck! no FAT found" 
yorika! I found It.

# File related checks
# From bash info page
`-a FILE' `-e FILE'
     True if FILE exists.
`-b FILE'
     True if FILE exists and is a block special file.
`-c FILE'
     True if FILE exists and is a character special file.
`-d FILE'
     True if FILE exists and is a directory.
`-f FILE'
     True if FILE exists and is a regular file.
`-g FILE'
     True if FILE exists and its set-group-id bit is set.
`-h FILE'
     True if FILE exists and is a symbolic link.
`-k FILE'
     True if FILE exists and its "sticky" bit is set.
`-p FILE'
     True if FILE exists and is a named pipe (FIFO).
`-r FILE'
     True if FILE exists and is readable.
`-s FILE'
     True if FILE exists and has a size greater than zero.
`-t FD'
     True if file descriptor FD is open and refers to a terminal.
`-u FILE'
     True if FILE exists and its set-user-id bit is set.
`-w FILE'
     True if FILE exists and is writable.
`-x FILE'
     True if FILE exists and is executable.
`-O FILE'
     True if FILE exists and is owned by the effective user id.
`-G FILE'
     True if FILE exists and is owned by the effective group id.
`-L FILE'
     True if FILE exists and is a symbolic link.
`-S FILE'
     True if FILE exists and is a socket.
`-N FILE'
     True if FILE exists and has been modified since it was last read.
`FILE1 -nt FILE2'
     True if FILE1 is newer (according to modification date) than
     FILE2, or if FILE1 exists and FILE2 does not.
`FILE1 -ot FILE2'
     True if FILE1 is older than FILE2, or if FILE2 exists and FILE1
     does not.
`FILE1 -ef FILE2'
     True if FILE1 and FILE2 refer to the same device and inode numbers.

bash$ [ -e /etc/fstab ] &&
>	echo "you have an 'fstab' so what!" || 
>	echo "Ooops! where is your fstab" 
you have an 'fstab' so what!

`INT1 -eq INT2'
`INT1 -ne INT2'
`INT1 -lt INT2'
`INT1 -le INT2'
`INT1 -gt INT2'
`INT1 -ge INT2'
     return true if INT1 is equal to, not equal to, less than,
     less than or equal to, greater than, or greater
     than or equal to INT2, respectively.
`-z STRING'
     True if the length of STRING is zero.
`-n STRING'
`STRING'
     True if the length of STRING is non-zero.
`STRING1 == STRING2'
     True if the strings are equal.  `=' may be used in place of `=='
     for strict POSIX compliance.
`STRING1 != STRING2'
     True if the strings are not equal.
`STRING1 < STRING2'
     True if STRING1 sorts before STRING2 lexicographically in the
     current locale.
`STRING1 > STRING2'
     True if STRING1 sorts after STRING2 lexicographically in the
     current locale.

if TEST-COMMANDS; then
	CONSEQUENT-COMMANDS;
elif TEST-COMMANDS; then
	CONSEQUENT-COMMANDS;
else	CONSEQUENT-COMMANDS;
fi

case WORD in
    PATTERN )	CONSEQUENT-COMMANDS ;;
    PATTERN1 | PATTERN2 )
		CONSEQUENT-COMMANDS ;;
esac
# PATTERN can have * ? [] .. etc

#!/bin/bash
# if.sh: a sample if statment script
read a
read b
if (( a < b)); then
	echo "$a is less than $b.";
else	echo "$a is greater than or equal to $b.";
fi

#!/bin/bash
# oddeven.sh: tell if a given number odd or even
  echo "enter a number"
  h=`read`
  let "remainder = h % 2"
  if [ "$remainder" -eq 0 ]   # Even?
  then
    echo "$h is even"
  else
    echo "$h is odd"
  fi

#!/bin/bash
# case.sh: a sample case statement script
echo -n "enter a color : "
read c
case $c in
    blue )
	echo "I like blue too.";;
    red )
	echo "red is not bad.";;
    green )
	echo "green is good.";;
    yellow | orange | cyan | magenta )
	echo "$c is not a basic color.";;
    * )
	echo "is $c a real color?";;
esac

# from BASH INFO
`*'
     Matches any string, including the null string.
`?'
     Matches any single character.
`[...]'
     Matches any one of the enclosed characters.  A pair of characters
     separated by a hyphen denotes a RANGE EXPRESSION; any character
     that sorts between those two characters, inclusive, using the
     current locale's collating sequence and character set, is matched.
     If the first character following the `[' is a `!'  or a `^' then
     any character not enclosed is matched.  A `-' may be matched by
     including it as the first or last character in the set.  A `]' may
     be matched by including it as the first character in the set.  The
     sorting order of characters in range expressions is determined by
     the current locale and the value of the `LC_COLLATE' shell
     variable, if set.

   If the `extglob' shell option is enabled using the `shopt' builtin,
several extended pattern matching operators are recognized.  In the
following description, a PATTERN-LIST is a list of one or more patterns
separated by a `|'.  Composite patterns may be formed using one or more
of the following sub-patterns:

`?(PATTERN-LIST)'
     Matches zero or one occurrence of the given patterns.
`*(PATTERN-LIST)'
     Matches zero or more occurrences of the given patterns.
`+(PATTERN-LIST)'
     Matches one or more occurrences of the given patterns.
`@(PATTERN-LIST)'
     Matches exactly one of the given patterns.
`!(PATTERN-LIST)'
     Matches anything except one of the given patterns.

until TEST-COMMANDS; do CONSEQUENT-COMMANDS ; done
while TEST-COMMANDS; do CONSEQUENT-COMMANDS ; done
for NAME in WORDS;  do CONSEQUENT-COMMANDS ; done
for (( EXPR1 ; EXPR2 ; EXPR3 )) ;  do CONSEQUENT-COMMANDS ; done
#you may use 'break' or 'continue'

#!/bin/sh
# gz-all.sh: replace all files with GZIPed version
for i in ./*
do
	gzip -9 "$i"
done

#!/bin/bash
# c-for.sh: c-like for loop
echo "this is a counter"
MAX=5
for ((i=1; i<=MAX; i++))
do
echo "$i"
done

#! /bin/sh
# func.sh : a script using functions

TellTime()
{
	echo "It's `date +%I:%M` now"
}
function SayHello()
{
	echo "Hello `whoami`"
	echo "It's a nice day"
}

# this is the main/global part
SayHello
TellTime

#! /bin/sh
# rect-area.sh : a script to find area of rectangle

# this function calc the rectangle area
RectArea()
{
	width="$1"
	height="$2"
	area=`echo "$width * $height" | bc`
	echo "$area"
}
# this is the main/global part
echo -n "Enter width: "
read width
echo -n "Enter height: "
read height
area=`RectArea $width $height`
echo "Area of rectangle=${width}x${height}=$area"

# rect-tool.sh: this is a tool lib for rect-client.sh
# it need not be executable (chmod -x)

function RectArea()
{
	width="$1"
	height="$2"
	area=$(echo "$width * $height" | bc)
	echo "$area"
}

#!/bin/bash
# rect-client.sh: main file of rectangle project!

. ./rect-tool.sh

# this is the main/global part
echo -n "Enter width: "
read width
echo -n "Enter height: "
read height
area=$(RectArea $width $height)
echo "Area of rectangle=${width}x${height}=$area"

#!/bin/sh
# findcds.sh: find IDE cdroms and fix the lins in /dev
if [ "$UID" = "0" ];then
	echo "Error: You must be a root run 'su' 1st."
	exit 1
fi
[ ! -d /proc/ide ] && mount none /proc -t proc || exit 1
echo -n "finding IDE CDROMs : "
cds=""
for i in hda hdb hdc hdd hde hdf hdg hdi hdj
do
    echo -n "."
    if [ -f /proc/ide/$i/media ];then
	dv=`cat /proc/ide/$i/media`
        [ "cdrom" = "$dv" ] && cds="$cds $i"
    fi
    echo -n "."
done
echo " OK. [$cds ]"
CDS_LIST="`echo "$cds " | sed -e 's/^ //'`"
echo -n -e "updating /dev/cdrom link ... "
CD=`echo "$CDS_LIST" | cut -d ' ' -f 1`
echo "/dev/$CD"
ln -sf "/dev/$CD" /dev/cdrom
CDS_LIST=`echo "$CDS_LIST" | cut -d ' ' -f 2-`
N="2"
for i in $CDS_LIST
do
    echo -n -e "updating /dev/cdrom$N link ... "
    echo "/dev/$i"
    ln -sf "/dev/$i" "/dev/cdrom$N"
    N=`expr $N + 1`    
done

#!/bin/sh
    rm /tmp/glassory.txt.tmp 2>/dev/null
for i in ./*.html
do
echo -n "processing [$i] ...    "
    cat $i | sed -e "s/[^0-9A-Za-z\\\/\-]/+/g" | 
    tr A-Z a-z | tr -s "+" "\012" |
    sed -e "s/^[0-9\\\/ ]*//g" >> /tmp/glassory.txt.tmp
echo " OK "
done
echo -n "sorting ... "
    cat /tmp/glassory.txt.tmp | sort | uniq > ./glassory.txt
    rm /tmp/glassory.txt.tmp
echo "done!"

trap "rm /tmp/mytmp" 2 3 9

#!/bin/bash
echo "Enter something, or try to send me a signal - CTRL+C -"
# 18 20 24 and 17 19 23 for CTRL+Z
# 2 3 9 for CTRL+C and kill -KILL
trap "echo 'Hi, we have a signal'" 18 20 24 17 19 23 2 3 9
read a