Windows quoting

[rovf]

My application generates at run time a Windows BAT file (oh you wonderful Windows Batch language - if I only knew which insane person had invented it!), which then in turn calls other programs (some compiled C application, some Perl programs). I need to pass strings from my Perl application via the Batch file to these programs (using the environment is no option here). For example:

my $some_argument='abc';
# ...
$batchfile=IO::File->new(">x.bat");
print $batchfile "\@echo off\nMyProg $some_argument\n";
$batchfile->close;
# ... later, in a different process ... :
system("x.bat"); # executes MyProg abc

That's the basic idea. Of course it is not so easy, because I don't know the content of $some_argument until at run-time, and this means I have to generate the argument in a way which is properly quoted according to Batch Language Syntax Rules.

I researched a bit how to do proper quoting in Windows batch files, and though a found a bit of information here and a bit of information there, I could not find a concise document which really describes it properly. So my first question is:

Does someone happen to know a CPAN module which implements Windows Batch Language quoting? Otherwise, does someone know the rules, so that I can implement it myself? So far, I found the following set of rules:

1. The special characters <>|^ must be escaped by ^ (for example, we have to convert 'a^b|c' into 'a^^b^|c')
2. A double quote at the beginning or at the end of the argument must be escaped by \ (for example, we have to convert '"ab"' to '\\"ab"\\')
3. If the argument contains spaces, it must be enclosed by double quotes, and in practice, it does not hurt to enclose the argument in double quotes always (for example, we have to convert 'a b' to '"a b"')
4. A double quote, which is followed by a space, must get a backslash in front (for example, we have to convert 'a" b' to 'a\" b')
5. If the argument starts with \", we are out of luck (at least I have not found yet a way how to encode the string '\\"foo' properly for my batchfile

Is this list complete or do I miss something?

[BrowserUk]

If the argument starts with \", we are out of luck (at least I have not found yet a way how to encode the string '\\"foo' properly for my batchfile

Using the following cmd file as the mechanism of demonstration (called echoem.cmd):

@echo off

perl -wle"print qq['$_'] for @ARGV" %*

Does this achieve what you are after?

C:\test>echoem "\"foo" "bar \"qux" \\\"foo
'"foo'            ### $1
'bar "qux'        ### $2
'\"foo'           ### $3

[rovf]

\\\"foo

Indeed it does! Thanks a lot!

[InfiniteSilence]

Are these batch files going to be reused in the future? If not, perhaps it would be best to do away with this mode of operation altogether and switch to using Win32::Process or something.

[rovf]

perhaps it would be best to do away with this mode of operation altogether and switch to using Win32::Process

The batch files are sent to a remote machine and executed there independently, at some unspecified later time. The remote execution mechanism *expects* Windows batch files. Basically, the only assumption we have on the remote machine is that it is a standard Windows system which can execute batch files.

[pc88mxer]

Instead of trying to quote $some_argument, can you pass it as an argument?

system("x.bat", $some_argument);

and then reference it in your batch script as %1 (or however batch scripts do this.)

[rovf]

Instead of trying to quote $some_argument, can you pass it as an argument?

No, because I do not call the batch file. A different process on a different machine calls the batch file, and it expects only a batch file, which will be invoked without parameters.