Shell Programming and Scripting

Hi,

So I have a very simple script which loops over 5 times and prints the iterator value.

Code:

#!/bin/sh
START=1
END=5
for i in $(eval echo "{$START..$END}")
do
        echo "$i"
done

If I save this script in a .sh file and run it in the terminal, the output I get is

Code:

{1..5}

But if I paste the same code in a terminal, I get the following

Code:

1
2
3
4
5

The second one is the expected output, but why is the first case not working as I expect?

I'm totally puzzled. Under cygwin the same code executes okay, but not in a unix shell..

Thanks.

Make sure you run it with bash or any recent shell instead of sh (in your shebang)...

Do you mean it works in the terminal as well as in script under cygwin? If yes, then there's a simple explanation for that: In cygwin /bin/sh is actually bash (https://cygwin.com/faq/faq.html#faq.using.shell-scripts).

Well, most likely /bin/sh there is in fact the good ol' bourne shell, which does not support the {$START..$END} bash feature. If you have bash installed there, you could simply change the shebang line from #!/bin/sh to #!/bin/bash and it should work. If not, you'll have to write a more portable code, try:

Code:

#!/bin/sh

START=1
END=5
while [ $START -le $END ]
do
 echo $START
 START=`expr $START + 1`
done

This should work at least with bash, sh and ksh.

On cygwin if you want a good shell to test bourne shell script try ash or dash

What is the exact operating system are you on when this occurs?