#!/usr/bin/bash
#if [ $# -lt 2 ] || [ $# -gt 2 ]
#if test $# -lt 2 -o $# -gt 2
#if [[ $# -lt 2 ]] || [[ $# -gt 2 ]]
if (($# < 2)) || (( $# > 2 ))
then
echo invalid
exit
else
echo file to be copied : $1
echo new file name : $2
cp $1 $2
echo copy successful
fi
#/usr/bin/bash
echo "Enter year"
read year
if [[ $(($year % 100)) -ne 0 ]]
#if (((year%100)!=0))
#if [ $(($year % 100)) -ne 0 ]
then
if [ $(($year%4)) -eq 0 ]
then
echo "Leap Year"
else
echo "Not a leap year"
fi
else
if [ $(($year % 400)) -eq 0 ]
then
echo "Leap Year"
else
echo "Not a leap year"
fi
fi
#!/usr/bin/bash
echo "enter a number"
read num
if [[ $num -ge 1 ]] && [[ $num -lt 10 ]]
then
echo "A"
elif [[ $num -ge 10 ]] && [[ $num -lt 90 ]]
then
echo "B"
elif [[ $num -ge 90 ]] && [[ $num -lt 100 ]]
then
echo "C"
else
echo "D"
fi
#!/bin/bash
echo "enter a number"
read num
if (( num >= 1)) && ((num<10))
then
echo "sam"
elif ((num >= 10)) && ((num < 90 ))
then
echo "ram"
elif ((num >= 90)) && ((num <100))
then
echo "rahim"
else
echo "tara"
fi
#!/bin/bash
echo "enter a number"
read num
if [ $num -ge 1 ] && [ $num -lt 10 ]
then
echo "A"
elif [ $num -ge 10 ] && [ $num -lt 90 ]
then
echo "B"
elif [ $num -ge 90 ] && [ $num -lt 100 ]
then
echo "C"
else
echo "D"
fi
#/bin/bash
echo "enter username to check"
read username
match=0
for line in `cat /etc/passwd`
do
if test `echo $line | cut -d ":" -f 1| cut -d "," -f 1` == $username ;
then
#match=$(($match+1))
#let "match=match+1"
#let "match++"
((match++))
fi
done
if [ $match -gt 0 ];
then
echo "$username is valid because match is $match"
else
echo "$username is not valid because match is $match"
fi
#!/bin/bash
# Create a new string
mystring="lets count the length of this string"
i=${#mystring}
echo "Length: $i"
Source:https://www.hostinger.in/tutorials/bash-script-example
#!/bin/bash
salary=1000
expenses=800
#Check if salary and expenses are equal
if test $salary == $expenses ;
then
echo "Salary and expenses are equal"
#Check if salary and expenses are not equal
elif test $salary != $expenses ;
then
echo "Salary and expenses are not equal"
fi
[ is actually a command, equivalent (almost, see below) to the test command. It's not part of the shell syntax. (Both [ and test, depending on the shell, are often built-in commands as well, but that doesn't affect their behavior, except perhaps for performance.)
An if statement executes a command and executes the then part if the command succeeds, or the else part (if any) if it fails. (A command succeeds if it exits with a status ($?) of 0, fails if it exits with a non-zero status.)
In
if [ "$name" = 'Bob' ]; then ...
the command is
[ "$name" = 'Bob' ]
(You could execute that same command directly, without the if.)
In
if grep -q "$text" $file ; then ...
the command is
grep -q "$text" $file
man [ or man test for more information.
FOOTNOTE: Well, the [ command is almost equivalent to the test command. The difference is that [ requires ] as its last argument, and test does not -- and in fact doesn't allow it (more precisely, test doesn't treat a ] argument specially; for example it could be a valid file name). (It didn't have to be implemented that way, but a [ without a matching ] would have made a lot of people very very nervous.)
Source:https://stackoverflow.com/questions/8934012/when-are-square-brackets-required-in-a-bash-if-statement
#!/bin/bash
# Create an indexed array
IndexedArray=(egg burger milk)
#Iterate over the array to get all the values
for i in "${IndexedArray[@]}";do echo "$i";done
Source:https://www.hostinger.in/tutorials/bash-script-example
use strict;
use warnings;
$|=1;
sub main{
my $output='output.txt';
open(OUTPUT,'>'.$output)or die "Can't create $output.\n";
print OUTPUT "Hello\n";
close(OUTPUT);
}
main();
use strict;
use warnings;
#disabling output buffering
$|=1;
sub main{
#my @files=('./a.txt','./b.txt','./c.txt',);
my $file='./a.txt';
open(INPUT,$file) or die("Input file $file not found.\n");
while(my $line=<INPUT>)
{
if($line=~/abc/)
{
print $line;
}
}
close(INPUT);
}
main();
use strict;
use warnings;
#disabling output buffering
$|=1;
sub main{
my @files=('./a.txt','./b.txt','./c.txt',);
#my $file='./a.txt';
foreach my $file(@files){
print "$file\n";
if(-f $file)
{
print "$file exists\n";
}
else
{
print "$file does not exist\n";
}
}
}
main();
else
{
print "$file does not exist\n";
}
}
}
main();
use strict;
use warnings;
sub main{
my $file='./a.txt';
if(-f $file)
{
print "$file exists\n";
}
else
{
print "$file does not exist\n";
}
}
main();
In the guest terminal
just enter:
explorer.exe . Source:https://superuser.com/questions/1185033/what-is-the-home-directory-on-windows-subsystem-for-linux #!/bin/bash
read -rep $'Please enter username\n' username
#echo "you have entered $username"
if [ `grep -c $username /etc/passwd` -eq 0 ]
then
echo "$username is invalid"
else
echo "$username is valid"
fi
use strict;
use warnings;
use LWP::Simple;
sub main{
print "Downloading ... \n";
#print get("http://www.google.com/");
#getstore("http://www.google.com","./source.code.html");
#to receive the response just as string we need to use single quote
#getstore('https://en.wikipedia.org/wiki/Main_Page#/media/File:Kathryn_Sullivan,_PCAST_Member_(cropped).jpg','face.jpg'>
my $code=getstore('https://en.wikipedia.org/wiki/Main_Page#/media/File:Kathryn_Sullivan,_PCAST_Member_(cropped).jpg','f>if($code==200)
{
print "Success\n";
}
else{
print "Failed\n";
}
print "Finished\n";
}
main();
use strict;
use warnings;
use LWP::Simple;
sub main{
print "Downloading ... \n";
#print get("http://www.google.com/");
getstore("http://www.google.com","./source.code.html");
print "Finished\n";
}
main();
use strict;
use warnings;
use LWP::Simple;
sub main{
print "Downloading ... \n";
print get("http://www.google.com/");
print "Finished\n";
}
main();
echo "enter extension"
read ext
for i in `find . -name "*.$ext" -type f`; do
# echo "$i"
echo `du -k "$i" | cut -f1`
done
echo "enter extension"
read ext
for i in `find . -name "*.$ext" -type f`; do
echo "$i"
done
#!/bin/bash
echo "Please enter extension"
read ext
total=0
for i in $(pwd)/*.$ext
do
#filesize=$((`stat --printf="%s" $i`))
#filesize=$((`wc -c $i | awk '{print $1}'))
filesize=$((`wc -c $i | cut -d " " -f 1`))
total=$(($total+$filesize))
done
echo "The total size of $ext files in present directory is $total"
#alternate way
#!/usr/bin/bash
read -rep $'Please enter the extension\n' ext
total=0
for i in `ls`
do
if [[ "$i" == *"$ext"* ]]
then
#echo $i
total=$(($total + `du -k $i | cut -f 1`))
fi
done
echo "The total size of $ext files is $total"
Some bash keyboard shortcuts
Some bash special characters
| Characters | Description |
|---|---|
| / | Directory separator, used to separate a string of directory names. Example: /home/projects/file |
| \ | Escape character. If you want to reference a special character, you must “escape” it with a backslash first. Example: \n means newline; \v means vertical tab; \r means return |
| # | Lines starting with # will not be executed. These lines are comments |
| . | Current directory. When its the first character in a filename, it can also “hide” files |
| .. | Returns the parent directory |
| ~ | Returns user’s home directory |
| ~+ | Returns the current working directory. It corresponds to the $PWD internal variable |
| ~- | Returns the previous working directory. It corresponds to the $OLDPWD internal variable |
| * | Represents 0 or more characters in a filename, or by itself, it matches all files in a directory. Example: file*2019 can return: file2019, file_comp2019, fileMay2019 |
| [] | Can be used to represent a range of values, e.g. [0-9], [A-Z], etc. Example: file[3-5].txt represents file3.txt, file4.txt, file5.txt |
| | | Known as “pipe". It redirects the output of the previous command into the input of the next command. Example: ls | less |
| < | It redirects a file as an input to a program. Example: more < file.txt |
| > | In script name >filename it will redirect the output of “script name” to “file filename”. Overwrite filename if it already exists. Example: ls > file.txt |
| >> | Redirect and append the output of the command to the end of the file. Example: echo "To the end of file" >> file.txt |
| & | Execute a job in the background and immediately get your shell back. Example: sleep 10 & |
| && | “AND logical operator”. It returns (success) only if both the linked
test conditions are true. It would run the second command only if the
first one ran without errors. Example: let "num = (( 0 && 1 ))"; cd/comp/projs && less messages |
| ; | “Command separator”. Allows you to execute multiple commands in a single line. Example: cd/comp/projs ; less messages |
| ? | This character serves as a single character in a filename. Example: file?.txt can represent file1.txt, file2.txt, file3.txt |
for i in 1 2 3 4 5
do
echo "Maharshi"
done
for i in {0..10..5}
do
echo -e "Maharshi\t$i"
done
for i in {10..0..-5}
do
echo -e "Maharshi\t$i"
done
for i in {1..10}
do
printf "%s\n%s\n" "Galgotias" "UNiversity";
done
for i in $(seq 1 10)
do
printf "%s\n%s\n" "Galgotias" "UNiversity";
done
for i in $(seq 1 2 10)
do
printf "i is %d\n" "$i";
done
for i in $(seq 10 -2 1)
do
printf "i is %d\n" "$i";
done
for((i=4;i<10;i++))
do
echo "Maharshi";
done
echo "enter a number";
read number;
if (((number < 10)) && ((number > 1)))||(((number<100))&&((number>90)))
then
echo $number;
fi
i=0
while ((i < 5 ))
do
echo "maharshi";
i=$(($i+1));
done
arithmatic expansion
i=15;
i=$(($i*5));
echo $i;
printf "Enter row number";
read n;
c=1
for((i=1;i<=(n-1);i++))
{
for((j=1;j<=(n-1);j++))
{
if(((i==j)||(j==(n-i))))
then
printf $c ;
else
printf " ";
fi
}
if ((c>=4))
then
((c=c-1));
else
((c=c+1));
fi
printf "\n";
}
apt-get install apache2
/sbin/a2enmod cgid
systemctl restart apache2
cd /usr/lib/cgi-bin
nano /usr/lib/cgi-bin/test.pl
#!/usr/bin/perl
print "Content-Type: text/html\n\n";
print ("<h1>Perl is working!</h1>");
even odd
echo "Please enter a number"
read num
if [ `expr $num % 2` == 0 ]
then
echo "$num is even"
else
echo "$num is odd"
fi
largest of three numbers
echo "please enter 3 numbers"
read num1
read num2
read num3
if test $num1 -gt $num2 -a $num1 -gt $num3
then
echo "$num1 is the greatest"
elif test $num2 -gt $num3
then
echo "$num2 is the greatest"
else
echo "$num3 is the greatest"
fi
calculate net salary
echo "enter basic salary"
read bs
hra=`echo $bs*10/100 | bc`
ta=`echo $bs*15/100 | bc`
da=`echo $bs*2/100 | bc`
pf=`echo $bs*10/100 | bc`
tax=`echo $bs*5/100 | bc`
netsal=`echo $bs+$hra+$ta+$da-$pf-$tax | bc`
echo "net salary is $netsal"
calculate conditional discount and tax
echo "please enter the amount that you want to buy"
read amount
if test $amount -lt 1000
then
tax=`echo $amount \* 2/100 | bc`
discount=`echo $amount \* 10/100 | bc`
else
tax=`echo $amount \* 5/100 | bc`
discount=`echo $amount \* 20/100 | bc`
fi
totalcost=`echo $amount - $tax + $discount | bc`
echo "total cost is $totalcost"