Creating My Own Escapes
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 \Stringn\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. James -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
Re: Creating My Own Escapes
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 \Stringn\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
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/ http://learn.perl.org/first-response
Re: Creating My Own Escapes
On Jan 16, 2004, at 3:38 PM, James Edward Gray II wrote: 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; Sorry to reply to my own post, but does this work? It seems to in all the test cases I can dream up: $string =~ s/\\([n\\])/$1 eq \\ ? $1 : \n/ge; James -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
Re: Creating My Own Escapes
On Jan 16, 2004, at 4:22 PM, Mark LoBue wrote:
I just had to do something like this yesterday, and I couldn't figure
out how to do it in just one regex, but I did find a way that you
could use. I have a database giving me single and double quotes in
variables as their octal equivalent. I get a variable from the
database as:
Dan\047s \042Baby\042
and I need the variable converted back to:
Dan's Baby
So, I did the following, @words is a list of variables to convert
# change octal \0nn to the appropriate character
foreach (@words) {
while ($_ =~ /\\(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.
Thanks for the suggestion.
I'm mostly concerned about the interaction of \\ and \n in pathological
cases like the string \\\n\n\\n. Which one do I convert first?
laughs
Since you're helping me, I'll give you a tip. The above loop is the
same as:
s/\\(0\d\d)/chr(oct $1)/ge foreach @words;
Thanks again.
James
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/ http://learn.perl.org/first-response
Re: Creating My Own Escapes
On Fri, Jan 16, 2004 at 03:38:40PM -0600 James Edward Gray II wrote:
I have a problem I just cant seem to get my head around, so any help is
appreciated.
I have a string. It could contain anything a Perl string can contain.
I have to print this string to a file and later bring it back in
exactly as it was. However, because of the file format, the string in
the file may not contain \n characters. That's the only difference
between the two representations of this string.
Okay, obviously I need to replace all \n characters. Let's say I want
to follow Perl's example and use a literal \ followed by a literal n.
Then I would also need to escape \ characters. Okay, again we'll use
Perl's \ and another \. Does that cover everything if \n is the only
illegal character in my file format? I believe, so, but please correct
me if I'm wrong.
Maybe B::perlstring() will do what you need:
[EMAIL PROTECTED]:~$ perl -lMB=perlstring -e '$var = \n\r\f; print perlstring( $var
bla\\\ \n )'
\n\r\f bla\\\ \n
Tassilo
--
$_=q#,}])!JAPH!qq(tsuJ[{@tnirp}3..0}_$;//::niam/s~=)]3[))_$-3(rellac(=_$({
pam{rekcahbus})(rekcah{lrePbus})(lreP{rehtonabus})!JAPH!qq(rehtona{tsuJbus#;
$_=reverse,s+(?=sub).+q#q!'qq.\t$.'!#+sexisexiixesixeseg;y~\n~~;eval
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/ http://learn.perl.org/first-response
Re: Creating My Own Escapes
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?
see if the following works better:
#!/usr/bin/perl -w
use strict;
my $o = my $s = Funky \St\nringn\n\n\n\n\n\n\n;
$s =~ s.\n.\\n.g;
$s =~ s.\\(?!n)..g;
print After encode: $s\n;
$s =~ s.\\n.\n.g;
$s =~ s..\\.g;
print they are ,$o eq $s ? :not ,same\n;
__END__
prints:
After encode: Funky St\nring\\\n\n\n\n\n\n\n\n
they are same
if the regx doesn't cover all cases, please post a few exceptions.
david
--
sub'_{print@_ ;* \ = * __ ,\ \}
sub'__{print@_ ;* \ = * ___ ,\ \}
sub'___{print@_ ;* \ = * ,\ \}
sub'{print@_,\n}{_+Just}(another)-(Perl)-(Hacker)
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/ http://learn.perl.org/first-response
Re: Creating My Own Escapes
On Jan 16, 2004, at 4:43 PM, Tassilo von Parseval wrote: Maybe B::perlstring() will do what you need: [EMAIL PROTECTED]:~$ perl -lMB=perlstring -e '$var = \n\r\f; print perlstring( $var bla\\\ \n )' \n\r\f bla\\\ \n I didn't know about that subroutine. Thank you very much! James -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
