Multi platform script perl or awk - regex

Question

I am trying to match records in following format:
(-,username,domain1.co.uk)\
(-,username,domain2.co.uk)
either awk or perl must be used. I am using cygwin and wrote following code which works and matches both above entries:
awk 'BEGIN {musr="(-,username,[^)]+.co.uk)"} {if ($0~musr) print $0}' netgroup
But if I try to modify this regexp to be more specific the output is nothing:
1st: match record then last backslash and then match newline:
"(-,username,[^)]+.co.uk)\\$"
2nd: match new line immediatelly after record without backslash:
"(-,username,[^)]+.co.uk)$"
So I decided to rewrite script into perl, hoping that perl can deal with backslashes and end of line symbols. For this purpose I used a2p this way:
echo 'BEGIN {musr="(-,username,[^)]+.co.uk)"} {if ($0~musr) print $0}' | a2p.exe
#!/usr/bin/perl
eval 'exec /usr/bin/perl -S $0 ${1+"$#"}'
if $running_under_some_shell;
# this emulates #! processing on NIH machines.
# (remove #! line above if indigestible)
eval '$'.$1.'$2;' while $ARGV[0] =~ /^([A-Za-z_0-9]+=)(.*)/ && shift;
# process any FOO=bar switches
$, = ' '; # set output field separator
$\ = "\n"; # set output record separator
$musr = '(-,username,[^)]+.co.uk)';
while (<>) {
chomp; # strip record separator
if ($_ =~ $musr) {
print $_;
}
}
This generated perl script also matches both entries, however if I try modify this script to more specific I get the following errors:
1st:
$musr = "(-,username,[^)]+.co.uk)\\";
Trailing \ in regex m/(-,username,[^)]+.co.uk)\/ at perlmatch.pl line 18, <> line 1.
2nd:
$musr = "(-,username,[^)]+.co.uk)$";
Final $ should be \$ or $name at perlmatch.pl line 14, within string
syntax error at perlmatch.pl line 14, near "= "(-,username,[^)]+.co.uk)$""
Execution of perlmatch.pl aborted due to compilation errors.
3rd:
$musr = "(-,username,[^)]+.co.uk)\$";
[the output is nothing]
What I am doing wrong ? My question is also pointing to fact that if somebody needs to use script on several platforms (aix, solaris, linux) than using perl should be better approach that dealing with (non)GNU utils and various (g|n)awk versions etc. Regards

Answer 1

Your problems arise from string quoting in Perl.
$musr = "(-,username,[^)]+.co.uk)\\"; replaces \\ with a single backslash when the string is created. But you would need to pass two backslashes to the regex. So you would have to put four in when you create the string.
$musr = "(-,username,[^)]+.co.uk)$"; tries to perform variable interpolation within the string.
In addition, parentheses should be escaped, as John Kugelman noted.
The solution is to use Perl's built-in delimiters for regular expressions, rather than normal quoted strings. The simple way is to put it right into your loop:
while (<>) {
chomp; # strip record separator
if ($_ =~ /\(-,username,[^)]+.co.uk\)$/) {
print $_;
}
}
If you do need to put the pattern into a variable first, use the special qr//
operator.
my $musr = qr/\(-,username,[^)]+.co.uk\)$/;
while (<>) {
chomp; # strip record separator
if ($_ =~ $musr) {
print $_;
}
}

Answer 2

(-,username,[^)]+.co.uk)\\$
The problem here is not with the backslash at the end of the line, it's the parentheses. Parentheses are used for grouping. You need to escape them to match literal ( ) characters. You should also escape the dots so they match literal dots instead of "any character".
$ awk '/\(-,username,[^)]+\.co\.uk\)$/ {print}' netgroup
(-,username,domain2.co.uk)
$ awk '/\(-,username,[^)]+\.co\.uk\)\\$/ {print}' netgroup
(-,username,domain1.co.uk)\
If you stick with plain awk and don't use [gn]awk-specific features awk is very portable. More portable than perl is, I would think.

Answer 3

Parentheses must be escaped. Otherwise they group expressions. To be more specific, match an optional backslash at the end of the line (Backslashes are doubled because as string they must be escaped too).
awk 'BEGIN {musr="\\(-,username,[^)]+.co.uk\\)\\\\?$"} {if ($0~musr) print $0}' netgroup