How to include pipe character in an argument to a batch file from a bash script?

Question

I have a shell script that I want to execute this line:

qtvars.bat vsstart "qt.sln" /BUILD "Debug|Win32"

This works fine (though I had to modify qtvars.bat, but that's beside the point). The problem is that I want the command to execute to be in a variable: EDIT: This doesn't work either, if I type it into bash. Previously I was typing it into cmd.exe, which hardly made for a fair comparison.

command="qtvars.bat"
args="vsstart"

$command $args "qt.sln" /BUILD "Debug|Win32"

Now it chokes on the pipe! I get this message:

'Win32' is not recognized as an internal or external command,
operable program or batch file.

I've tried a bunch of forms of escaping the quotes and/or pipe, all to no avail. Interestingly, it works when it's an executable rather than a batch file, e.g.:

command="devenv.exe"
args=""

$command $args "qt.sln" /BUILD "Debug|Win32"

Thanks for any ideas.

Answer 1

Hello,

This is a classic case of double-escaping, where both bash and CMD.EXE need to be instructed to ignore the special | (pipe) character.

Try the following:

$command $args "qt.sln" /BUILD '"Debug|Win32"'

This will be the equivalent of you typing, at a CMD.EXE prompt:

qtvars.bat vsstart qt.sln /BUILD "Debug|Win32"

Using the above, you are essentially forcing the passing of the double-quotes on to CMD.EXE (instead of bash eating them away.) The outermost single quotes instruct bash not to interpret or touch in any way what's inside them; the inner double-quotes instruct CMD.EXE to ignore any special characters (the pipe in this case) within.

Alternatively, you can also try:

$command $args "qt.sln" /BUILD 'Debug\|Win32'

This should be the equivalent of you typing, at a CMD.EXE prompt:

qtvars.bat vsstart qt.sln /BUILD Debug\|Win32

Note the use of single quotes (!), which ensure that bash will not interpret the \ (and, instead, will pass it as-is to CMD.EXE.)

Cheers, V.

Answer 2

Interesting! What does escaping the | do?

Do these work?

• echo "Debug|Win32"
• echo "qt.sln" /BUILD 'Debug|Win32'

Answer 3

I'm really thinking this is a bug in Cygwin's bash.

It still fails when I rewrite the line like this:

eval "$command $args \"qt.sln\" /BUILD \"Debug|Win32\""

So taking Vlad R's mention of CMD.EXE as a hint, I tried this instead:

cmd.exe /c "$command $args \"qt.sln\" /BUILD \"Debug|Win32\""

And it works. Oddly enough, without the .exe, it doesn't work. Oh, and now it gives me grief if $command has spaces in it. Yes, I've tried putting \" on either side of it and/or running it through cygpath -w first. That's for another day because I've wasted enough time on this triviality already! (I can get around it all by just specifying Debug instead of Debug|Win32.)