Question

I’m trying to write a simple bash script but something seems wrong, I’m testing the following on the command line:

DATE="2010-09-{10,11}"
result=`\ls *ext.$DATE.Z`

and results in ls: cannot access *ext.2010-09-{10,11}.Z: No such file or directory

but if I execute this:

result=`\ls *ext.2010-09-{10,11}.Z`

it works flawlessly…

I even tried to remove the quotation marks from DATE parameter but that isn’t the problem, bash manual isn’t helping, what am I doing wrong? Wasn’t it supposed to execute parameter substitution and pass it to my command?

I thought I should have to escape the $ sign but that didn’t work either.

EDIT – Explanation on purpose added

What I am trying to accomplish is to populate variable result with all filenames that match the given pattern (*ext.2010-09-{10,11}), I know I can solve this using a for cycle but I thought about using curly braces for shortness.

Answer 1

The issue is when you execute it directly on the command line \ls *ext.2010-09-{10,11}.Z is a short form that’s expanded into two commands: ls *ext.2010-09-10.Z and ls *ext.2010-09-11.Z (by the command line – each subsequently called). ls itself doesn’t directly support an expression like that, so when you build it into a script, it’s getting the literal string which it doesn’t understand.

Brace Expansion is not supported by all command lines, and isn’t recommended for shell scripts:

Brace expansions should not be used in
portable shell scripts, because the
Bourne shell will not produce the same
output.

Here’s a solution-script:

#!/bin/sh
DAYS="10 11"
for i in $DAYS;
do
  ls *ext.2010-09-$i.Z
done