How to use variable in a range like {a..b}?

[Peng Yu]

x=10
for i in {1..$x}; do echo $i; done

The above code give me
{1..10}

, rather than printing numbers from 1 to 10.

I'm wondering how to use variable in a range?

-- 
Regards,
Peng

Re: How to use variable in a range like {a..b}?

[Roman Rakus]

On 05/12/2010 01:27 PM, Peng Yu wrote:

x=10
for i in {1..$x}; do echo $i; done

The above code give me
{1..10}

, rather than printing numbers from 1 to 10.

I'm wondering how to use variable in a range?

   

This works for me;
x=10; for i in $(eval echo {1..$x}); do echo $i; done
But is not so cute.
RR

Re: How to use variable in a range like {a..b}?

[Greg Wooledge]

On Wed, May 12, 2010 at 06:27:43AM -0500, Peng Yu wrote:
> x=10
> for i in {1..$x}; do echo $i; done

That won't work because of the way bash does its parsing.  Brace expansion
is done before parameter (variable) expansion.  Since the brace-expansion
part doesn't see 1..10 it can't generate a list of integers.

> I'm wondering how to use variable in a range?

for ((i=1; i<=x; i++)); do ...

... is the way I'd do it.


On Wed, May 12, 2010 at 01:57:35PM +0200, Roman Rakus wrote:
> This works for me;
> x=10; for i in $(eval echo {1..$x}); do echo $i; done
> But is not so cute.

There's also the more traditional (and POSIX-compatible):

x=10; i=1; while [ $i -le $x ]; do ...; i=$(($i+1)); done