#!/bin/bash
# Basic while loop
counter=1
while [ $counter -le 10 ]
do
    echo $counter
    ((counter++))
done
echo All done

#!/bin/bash
# Basic until loop
counter=1
until [ $counter -gt 10 ]
do
    echo $counter
    ((counter++))
done
echo All done

#!/bin/bash
echo "Print the numbers which are even and divisible by 5"
counter=1
while [ $counter -le 20 ]
do
    if [[ $counter%2 -eq 0 && $counter%5 -eq 0 ]]
    then
        echo "$counter"
    fi
    ((counter++))
done
echo "Done"

$ bash while.sh
Print the numbers which are even and divisible by 5
10
20
Done

#!/bin/bash
n=20
until [ $n -lt 0 ]
do
    if [[ $n%2 -gt 0 ]]
    then
        echo $n
    fi
    ((n=$n-1))
done

$ bash until.sh
19
17
15
13
11
9
7
5
3
1

for var in list
do
    commands
done

#!/bin/bash
for day in Monday Tuesday Wednesday Thursday Friday Saturday Sunday
do
    if [[ $day == 'Monday' || $day == 'Thursday' ]]
    then
        echo "Meeting on $day at 9:30 am"
    elif [[ $day == 'Tuesday' || $day == 'Wednesday' || $day == 'Friday' ]]
    then
        echo "Training on $day at 11:00 am"
    else
        echo "$day is Holiday"
    fi
done

$ bash for.sh
Meeting on Monday at 9:30 am
Training on Tuesday at 11:00 am
Training on Wednesday at 11:00 am
Meeting on Thursday at 9:30 am
Training on Friday at 11:00 am
Saturday is Holiday
Sunday is Holiday

#!/bin/bash
planets='Mercury Venus Earth'
for planet in $planets
do
    echo $planet
done
echo All done

#!/bin/bash
planets='Mercury Venus Earth'
for planet in "$planets"
do
    echo $planet
done
echo All done

$ bash for_loop.sh
Mercury
Venus
Earth
All done

$ bash for_quoted.sh
Mercury Venus Earth
All done

#!/bin/bash
for ((num = 1; num <= 5; num++))
do
    echo $num
done
echo All done

#!/bin/bash
# Make a php copy of any html files
for value in $1/*.html
do
    cp $value $1/$( basename -s .html $value ).php
done

$ ls site
about.html  index.html
$ bash copy_html.sh site
$ ls site
about.html  about.php  index.html  index.php

#!/bin/bash
echo "Argument values are: $1 $2"
for arg in "$@"
do
    key=$(echo $arg | cut -f1 -d=)
    value=$(echo $arg | cut -f2 -d=)
    case $key in
        id) echo "Student ID = $value";;
        mark) echo "Obtained mark = $value";;
        *)
    esac
done

$ bash cl2.sh id=2026101 mark=90
Argument values are: id=2026101 mark=90
Student ID = 2026101
Obtained mark = 90

#!/bin/bash
for value in {22..30}
do
    if (( value % 7 == 0 ))
    then
        echo "found $value"
        break
    fi
    echo "checked $value"
done
echo All done

$ bash break_demo.sh
checked 22
checked 23
checked 24
checked 25
checked 26
checked 27
found 28
All done

#!/bin/bash
for value in $1/*
do
    if [ ! -r $value ]
    then
        echo $value not readable 1>&2
        continue
    fi
    cp $value backup/
    echo "backed up $value"
done

$ ls notes
a.txt  b.txt  secret.txt
$ bash copy_check.sh notes
backed up notes/a.txt
backed up notes/b.txt
notes/secret.txt not readable
$ ls backup
a.txt  b.txt

echo "Reading file using cat command"
content=`cat hardware.txt`
echo $content
echo "Reading file line by line using loop"
while read line
do
    echo $line
done < hardware.txt

$ bash readfile.sh
Reading file using cat command
Monitor Keyboard Mouse Scanner Printer
Reading file line by line using loop
Monitor
Keyboard
Mouse
Scanner
Printer

$ bash select_example.sh
1) Mars
2) Venus
3) Earth
4) Quit
Select planet: 2
Hello Venus
Select planet: 1
Hello Mars
Select planet: 5
Hello
Select planet: 4
Bye

#!/bin/bash
# Basic function
print_something () {
    echo Hello I am a function
}
print_something
print_something

$ bash function_example.sh
Hello I am a function
Hello I am a function

#!/bin/bash
# Passing arguments to a function
print_something () {
    echo Hello $1
}
print_something Mars
print_something Jupiter

$ bash arguments_example.sh
Hello Mars
Hello Jupiter

#!/bin/bash
# Setting a return status for a function
print_something () {
    echo Hello $1
    return 5
}
print_something Mars
print_something Jupiter
echo The previous function has a return value of $?

$ bash return_status_example.sh
Hello Mars
Hello Jupiter
The previous function has a return value of 5

#!/bin/bash
# Setting a return value to a function
lines_in_file () {
    cat $1 | wc -l
}
num_lines=$( lines_in_file $1 )
echo The file $1 has $num_lines lines in it.

#!/bin/bash
# Experimenting with variable scope
var_change () {
    local var1='local 1'
    echo Inside function: var1 is $var1 : var2 is $var2
    var1='changed again'
    var2='2 changed again'
}
var1='global 1'
var2='global 2'
echo Before function call: var1 is $var1 : var2 is $var2
var_change
echo After function call: var1 is $var1 : var2 is $var2

Before function call: var1 is global 1 : var2 is global 2
Inside function: var1 is local 1 : var2 is global 2
After function call: var1 is global 1 : var2 is 2 changed again

print_message
ret_strdata
echo $return_str
echo "Enter the radius value"
read rad
calculate_area $rad

$ bash func.sh
Bash programming for beginner
Learn bash programming with functions
Enter the radius value
4
Area of the circle is 50.24

#!/bin/bash
# Create a wrapper around the command ls
ls () {
    command ls -lh
}
ls

$ bash override.sh
total 4.0K
-rwxr-xr-x 1 student student 85 Sep 25 09:00 override.sh

#!/bin/bash
echo "Enter a numeric value"
read n
if [[ $n -le 100 ]]
then
    exit 0
else
    exit 1
fi

#!/bin/bash
bash "first.sh"
if [ $? -eq 1 ]
then
    echo "The input number is greater than 100"
else
    echo "The input number is less than or equal to 100"
fi

#!/bin/bash
counter=10
until [ $counter -lt 4 ]
do
    echo -n "$counter "
    ((counter-=3))
done
echo
for value in {15..3..4}
do
    echo -n "$value "
done
echo

#!/bin/bash
for n in {1..10}
do
    if [[ $n%2 -eq 0 ]]
    then
        echo "$n is even"
    else
        echo "$n is odd"
    fi
done

$ bash even_odd.sh
1 is odd
2 is even
3 is odd
4 is even
5 is odd
6 is even
7 is odd
8 is even
9 is odd
10 is even

grade () {
    local mark=$1
    if [ $mark -ge 85 ]
    then
        echo A
    elif [ $mark -ge 65 ]
    then
        echo B
    else
        echo C
    fi
}

for m in 92 70 40 85
do
    g=$( grade $m )
    echo "mark $m gets $g"
done

#!/bin/bash
count=0
add () {
    local step=$1
    count=$(( count + step ))
    step=100
}
step=7
add 5
add 3
echo "count=$count step=$step"

valid () {
    if [[ $1 -ge 0 && $1 -le 100 ]]
    then
        return 0
    else
        return 1
    fi
}

for m in 45 120 100 -3
do
    valid $m
    if [ $? -eq 0 ]
    then
        echo "$m ok"
    else
        echo "$m invalid"
    fi
done

#!/bin/bash
n=0
while read line
do
    ((n++))
    echo "$n: $line"
done < hardware.txt
echo "Total: $n lines"

$ bash number_lines.sh
1: Monitor
2: Keyboard
3: Mouse
4: Scanner
5: Printer
Total: 5 lines