Loop variable error in for loop

When I’m using for like

 for i in 1 2 3 4 5 

then my file contains #!/bin/sh at the top.

But when I’m using

for(( i = 0; i<=5; i++))

then it is showing error

Syntax error: Bad for loop variable

and running properly when I remove shebang. Please tell me the reason behind this.

4 Answers

for(( i = 0; i<=5; i++)) is Bash specific and doesn't work with plain Bourne shell (/bin/sh).

If you remove the shebang the script is run by your current shell (which likely is Bash) so it works.

Replace #!/bin/sh with #!/bin/bash to make the shebang work.

for(( i = 0; i<=5; i++))

for this type of loop only runs on Bash shell. so, if you want to run this, then try this command :

$bash filename.sh

I think It will work fine. and see this one also.

I have solved this problem by using ./ instead of sh command. For an example if you put sh test.sh instead just make your command as ./test.sh And most probably problem will be solved.

Try this out may be this could solve your problem

#!/bin/bash
j=0
for (( i=1; i <= 5; i++ ))
do echo "the loop is runing $i time: and value of j is $j" j=`expr $j + 1`
done