How to escape white space in command line arguments

[GoForIt]

Hello,

I'm trying to call a Perl script from another passing few arguments. One of my arguments has a path variable which has white spaces embedded in it. I know how to escape the white space when I know the value of the variable in advance. But how do I escape the white spaces in a scalar variable that's being passed as an argument to a script called inside another script.

For instance, we could escape the white space and read $path as one whole string till the end

 my $path = "C:/\"Program Files\"/\"Perl Express\"/example.txt;

Now, I'm trying to pass one such $path variable and a hash as arguments to a script.

@ARGV = ("C:/Program Files/Perl Express/sample.txt", "some hash"); # I
+ dunno the path value in advance. This is just an example
system("C:/Perl/bin/perl.exe /path/to/the/script @ARGV");

When I try to print this ARGV in the other script, it reads C:/Program and Files/Perl as first and second arguments.

Is there a way that I could escape such white spaces?

Thanks,

[repellent]

Is there a way that I could escape such white spaces?

Yes, by avoiding the escape effort.

Keep arguments separate by maintaining them in a list - don't interpolate the array into the string:


my @args = ("C:/Program Files/Perl Express/sample.txt", "some hash");
system($^X, "/path/to/the/script", @args);

[GoForIt]

Hi,

That works. I was passing the @args in double quotes and that's precisely was the mistake.

Thanks for helping me out.

Thanks,

[Marshall]

On Windows, you just double quote command line args that have spaces. @ARGV should be a read_only thing for a user. 2 simple Perl scripts and how they can interact:

#!/usr/bin/perl -w
use strict;
#file: testargv.pl

my $parms = 'a b c abc "some gizmo" d32';
print `perl argv.pl $parms`;

__END__
prints
a
b
c
abc
some gizmo
d32

===== file argv.pl ========
#!/usr/bin/perl -w
use strict;
#file: argv.pl

foreach (@ARGV)
{
   print "$_\n";
}

==example of command line input to argv.pl ====
C:\TEMP>perl argv.pl "some thing" "some other thing" d x "xy z"
some thing
some other thing
d
x
xy z

[JavaFan]

@ARGV should be a read_only thing for a user.

This raises several questions.
1. What has the ability to write @ARGV to do with the problem?
2. Why should it be read_only? Why isn't it read_only if it should?
3. Who's the user in this case? The programmer? The person running the code?

[Marshall]

Well I just saw this from the OP:
@ARGV = ("C:/Program Files/Perl Express/sample.txt", "some hash");

@ARGV is a special Perl variable that contains the command line arguments. A similar thing exists in other languages. In 'C' you also get argc which is the count of the argv strings, e.g. int main(int argc, char **argv), but argc is redundant because argv is a null terminated array of pointers to strings and therefore calculating argc is trivial. Perl uses @ARGV for the purpose of passing command line args and the scalar value of @ARGV is what 'C' calls argc.

Nobody but the O/S should set @ARGV.

[Marshall]

my $path = "C:/\"Program Files\"/\"Perl Express\"/example.txt;

This should be re-written. There is no need to "escape" double quotes - the whole path name should be in quotes, this \" doesn't make sense. Under Windows Perl, the following Perl $path name is completely valid:


#!/usr/bin/perl -w
use strict;

my $path = "C:/Program Files/Perl Express/example.txt";
#there is no need to "escape" the double quotes.
print "$path\n";
my $root = "C:/Program Files/Perl Express";
my $somefile = "X Y Z.dat";
my $somefile_path = "$root/$somefile";
print "$somefile_path\n";

__END__
prints:
C:/Program Files/Perl Express/example.txt
C:/Program Files/Perl Express/X Y Z.dat

[GoForIt]

Hi,

Yes, you're right. For some reason, it wasn't working before so I chose to escape those white spaces which turned out to be totally unnecessary later.

I really appreciate your response.

Thanks,

Off the topic, could someone please tell me if I need to close the thread in this forum? I read the FAQs and I couldn't find any related posts there. I just want to make sure that I follow the forum rules. Thanks!

[repellent]

Off the topic, could someone please tell me if I need to close the thread in this forum?

There is no need to. This is a good thread that will, in the future, help people who come by it.

[Marshall]

GoForIt, I'm glad that you got some help from this thread and are able to proceed with your program! Hurray!

This @ARGV business just means that this is a reserved array for Perl and normally you shouldn't assign to it or grow it by a push or whatever. I've never seen a 'C' or Perl program that did that, but of course "never" is a very long time!

Perl normally "consumes" items from @ARGV via shift. The equivalent analog in 'C' is argv++. Getopts essentially works this way. Both of these operations make @ARGV smaller. There are also analogous operations that can consume the "rightmost" argument from the command line.

JavaFan and I are probably in what I would call "aggressive agreement" - there isn't any real difference except that somehow the words via text seem to be in juxtaposition.

[Anonymous Monk]

perldoc -f system

my( @args ) = ( $^X, "one", "two" );
system( { $args[0] } @args ) == 0
     or die "system @args failed: $?"

[nvivek]

If you want to escape the spaces in the string of an array.You try the following,

my %hash=(1=>"one");
my $str='C:/Program Files/Perl Express/sample.txt';
$str=~s/ /\\ /g;
@ARGV = ($str,%hash);
system("./script.pl @ARGV");

In the script.pl,I printed the array @ARGV. It printed the Path and hash keys and values correctly.