Re: [[ ]] test always reports a "not found" error in bash shell script

["Cliff Hones" <cliff at aonix dot co dot uk>]

MATTHEWS,MICHAEL (HP-Vancouver,ex1) <mmatthews@hp.com> wrote:
> I am porting a Linux build system to Windows XP by using the Cygwin
1.3.22-1
> environment (see the attached text file for output from "cygcheck -s -v
> -r"). All of the bash shell scripts use the [[ ]] test in if statements,
> similar to:
>
>   if [[ "$(uname -s)" != "Linux" ]]
>   then
>     # Do Cygwin stuff
>   else
>     # Do Linux stuff
>   fi
>
> Whenever I run the script in the Cygwin bash shell, the conditional
> executes, but the following error is displayed in the terminal window:
>
>   [[: not found
>
> If I replace the double square brackets with single square brackets:
>
>   if [ "$(uname -s)" != "Linux" ]
>   then
>     # Do Cygwin stuff
>   else
>     # Do Linux stuff
>   fi
>
> I do not get any error message.
>
> I use the [[ ]] test because from what I read about the bash shell
> conditional testing, using [[ ]] is better than [ ], since [[ ]] is tested
> internally, whereas [ ] is tested in a separate shell with the "test"
> command. I would prefer to not have to change all of the test conditionals
> in our Linux bash shell scripts from [[ ]] to [ ].
>
> I checked the versions of bash in Cygwin and in Linux and they are:
>
>   Cygwin bash version : GNU bash, version 2.05b.0(9)-release
> (i686-pc-cygwin)
>   Linux bash version  : GNU bash, version 2.05b.0(1)-release
> (i686-pc-linux-gnu)

By default the shell for command scripts (/bin/sh) is ash not bash on
Cygwin.
You may be inadvertently using ash.  To use bash start your
scripts with #!/bin/bash.

-- Cliff


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