At 01:38 PM 1/16/2004, James Edward Gray II wrote:
>I have a problem I just cant seem to get my head around, so any help is appreciated.
>
>I have a string. It could contain anything a Perl string can contain.
>I have to print this string to a file and later bring it back in exactly as it was.
>However, because of the file format, the string in the file may not contain \n
>characters. That's the only difference between the two representations of this
>string.
>
>Okay, obviously I need to replace all \n characters. Let's say I want to follow
>Perl's example and use a literal \ followed by a literal n.
>Then I would also need to escape \ characters. Okay, again we'll use Perl's \ and
>another \. Does that cover everything if \n is the only illegal character in my file
>format? I believe, so, but please correct me if I'm wrong.
>
>The to file conversion seems simple given the above:
>
>$string =~ s/\\/\\\\/g;
>$string =~ s/\n/\\n/g;
>
>Does that work as good as I think it does?
>
>Now I have to get it back out of the file and that's where it falls apart on me.
>I've tried things like:
>
>$string =~ s/((?:^|[^\\])(?:\\\\)*)\\n/$1\n/g;
>$string =~ s/\\\\/\\/g;
>
>While that gets close, it doesn't seem to work on everything. Here's an example
>(one-liner reformatted for easier reading):
>
>perl -e ' $test = "\tFunky \"String\"\\\n\n";
> print "String: $test\n";
> $test =~ s/\\/\\\\/g;
> $test =~ s/\n/\\n/g;
> print "To File: $test\n";
> $test =~ s/((?:^|[^\\])(?:\\\\)*)\\n/$1\n/g;
> $test =~ s/\\\\/\\/g;
> print "From File: $test\n" '
>String: Funky "String"\
>
>
>To File: Funky "String"\\\n\n
> From File: Funky "String"\
>\n
>
>Any advice is appreciated.
I just had to do something like this yesterday, and I couldn't figure out how to do it
in just one regex, but I did find a way that you could use. I have a database giving
me single and double quotes in variables as their octal equivalent. I get a variable
from the database as:
Dan\047s \042Baby\042
and I need the variable converted back to:
Dan's "Baby"
So, I did the following, @words is a list of variables to convert
# change octal \0nn to the appropriate character
foreach (@words) {
while ($_ =~ /\\(0\d{2})/) {
my $myChar = chr(oct $1);
$_ =~ s/\\$1/$myChar/g;
}
}
This works, but I am sure there is a better way to code this, and I was thinking of
asking that when I had time. To use it, instead of coverting newlines to \n, convert
them to \012.
-Mark
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