regex basics

jott19 has asked for the wisdom of the Perl Monks concerning the following question:

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Re: regex basics by CountZero (Bishop) on Jan 31, 2015 at 08:18 UTC
Welcome to the world of Perl! Strange (or not) as it may be, "`perl`" is not a keyword within Perl! You are actually mixing up the Perl "one liner" style and proper scripting style. Script: `use Modern::Perl qw /2014/; my $iniprod = 'php.ini-production'; my $ininocm = 'php.ini-nocomments'; open my $IN, '<', $iniprod or die "Could not open $iniprod for readin +g: $!"; open my $OUT, '>', $ininocm or die "Could not open $ininocm for writin +g: $!"; while (<$IN>) { print $OUT $_ unless /;\s+/ ; } close $IN or die "Error closing $iniprod: $!"; close $OUT or die "Error closing $ininocm: $!";` [download] CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply] [d/l] [select]
Re^2: regex basics by AnomalousMonk (Archbishop) on Jan 31, 2015 at 16:43 UTC
`print $OUT $_ unless /;\s+/ ;` I'm not familiar with the syntax or conventions of PHP `.ini` files, but wouldn't the quoted statement eliminate lines of the format `some_directive ; this directive does such and such` also? Give a man a fish: `<%-(-(-(-<`	[reply] [d/l] [select]
Re^3: regex basics by CountZero (Bishop) on Feb 02, 2015 at 08:48 UTC
That is very well possible. I just used the basic regex in the OP's post. `/^;\s+/` is probably better, but I don't know PHP enough to be sure. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply] [d/l]
Re^2: regex basics by jott19 (Initiate) on Feb 01, 2015 at 01:36 UTC
Hi CountZero and thanks for the reply. I tried this (using CentOS 6.6): `#!/usr/bin/env perl use Modern::Perl qw /2014/; my $iniprod = 'php.ini-production'; my $ininocm = 'php.ini-nocomments'; open my $IN, '<', $iniprod or die "Could not open $iniprod for readin +g: $!"; open my $OUT, '>', $ininocm or die "Could not open $ininocm for writin +g: $!"; while (<$IN>) { print $OUT $_ unless /;\s+/ ; } close $IN or die "Error closing $iniprod: $!"; close $OUT or die "Error closing $ininocm: $!";` [download] results: `[/etc/php.d] # ./php.ini-remove-comments.pl Can't locate Modern/Perl.pm in @INC (@INC contains: /usr/local/lib64/p +erl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/p +erl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5 .) at ./php.ini-re +move-comments.pl line 2. BEGIN failed--compilation aborted at ./php.ini-remove-comments.pl line + 2.` [download] I checked... `[/etc/php.d] # perl -v This is perl, v5.10.1 (*) built for x86_64-linux-thread-multi` [download] The release date for 5.10.1 was 2009-Aug-06. Apparently a lot has changed in 5 years... latest version at 5.21.3? I commented 'use Modern::Perl qw /2014/;' and it worked perfectly--except it left blank lines like tombstones where the comments used to be. I thought another pass would do it: 1 #!/usr/bin/env perl 2 # use Modern::Perl qw /2014/; 3 4 my $iniprod = 'php.ini-production'; 5 my $ininocm = 'php.ini-nocomments'; 6 7 open my $IN, '<', $iniprod or die "Could not open $iniprod fo +r reading: $!"; 8 open my $OUT, '>', $ininocm or die "Could not open $ininocm fo +r writing: $!"; 9 10 while (<$IN>) { 11 print $OUT $_ unless /;\s+/; 12 } 13 while (<$OUT>) { 14 print $OUT $_ unless /\n+/; 15 } 16 close $IN or die "Error closing $iniprod: $!"; 17 close $OUT or die "Error closing $ininocm: $!"; 18 [download] did not work. I tried to come up with something like this... `#!/usr/bin/env perl # use Modern::Perl qw /2014/; my $iniprod = 'php.ini-production'; my $ininocm = 'php.ini-nocomments'; open my $IN, '<', $iniprod or die "Could not open $iniprod for readin +g: $!"; open my $OUT, '>', $ininocm or die "Could not open $ininocm for writin +g: $!"; while (<$IN>) { if (!$_ /;\s+/) { print $OUT $_ } } close $IN or die "Error closing $iniprod: $!"; close $OUT or die "Error closing $ininocm: $!";` [download] but I'm getting an error... `Substitution pattern not terminated` Is this any different form 'print OUT $_ unless...' ? Should I use chomp here?	[reply] [d/l] [select]
Re^3: regex basics by poj (Abbot) on Feb 01, 2015 at 13:29 UTC
Try #!/usr/bin/env perl use strict; use warnings; my $iniprod = 'php.ini-production'; my $ininocm = 'php.ini-nocomments'; my $log = 'removed.log'; open my $IN, '<', $iniprod or die "Could not open $iniprod for reading: $!"; open my $LOG, '>', $log or die "Could not open $log for writing: $!"; my $count=0; my $text; while (<$IN>) { ++$count; if (/;\s+/) { print $LOG "$count : $_"; } else { $text .= $_; } } close $IN or die "Error closing $iniprod: $!"; # squash multiple blank lines to one $text =~ s{\n{3,}}{\n\n}gm; open my $OUT, '>', $ininocm or die "Could not open $ininocm for writing: $!"; print $OUT $text; close $OUT or die "Error closing $ininocm: $!"; __DATA__ line 1 ; this directive does such and such ; and some more ;some_directive line 2 line 3 line 4 line 5 [download] poj	[reply] [d/l]
Re^4: regex basics by jott19 (Initiate) on Feb 01, 2015 at 21:51 UTC
Re^3: regex basics by CountZero (Bishop) on Feb 02, 2015 at 13:12 UTC
Modern::Perl is indeed for more recent versions of Perl. I'm running Perl 5.18. You can safely delete it in this script and add `use strict; use warnings;` in its place. Those blank lines you see are mysterious. There shouldn't be any such lines as nothing is printed when a comment is found. `!$_ /;\s+/` is invalid syntax and confused the Perl-interpreter hence the rather unhelpful error message. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply] [d/l] [select]
Re^4: regex basics by jott19 (Initiate) on Feb 02, 2015 at 14:01 UTC
Re^5: regex basics by choroba (Cardinal) on Feb 02, 2015 at 15:28 UTC
Some notes below your chosen depth have not been shown here
Re: regex basics by Anonymous Monk on Jan 31, 2015 at 10:02 UTC
Start with perlintro	[reply]
Re^2: regex basics by pme (Monsignor) on Jan 31, 2015 at 10:41 UTC
and continue with perlretut.	[reply]
Re: regex basics by karlgoethebier (Abbot) on Feb 02, 2015 at 15:23 UTC
I suggest this: `#!/usr/bin/perl while(<>) { next if /;{2,}/; next if /;\s{1}/; print unless /^\n/; } __END__ strip_ini.pl php.ini [PHP] ;user_ini.filename = ".user.ini" ;user_ini.filename = ;user_ini.cache_ttl = 300 engine = On short_open_tag = Off asp_tags = Off precision = 14 y2k_compliance = On output_buffering = 4096 ;output_handler = zlib.output_compression = Off ;zlib.output_compression_level = -1 ...about 300 lines more` [download] Usage: `strip_ini.pl php.ini > php.stripped.ini` Note: `;;;;;;;;;;;;;;;;;;; <-- the first next skips the ASCI art ; About php.ini ; <-- the second next skips the explanations ;;;;;;;;;;;;;;;;;;;` [download] The `print unless /^\n/` prevents unwanted printing of emtpy lines. I don't know for the moment why they are there... Best regards, Karl �The Crux of the Biscuit is the Apostrophe�	[reply] [d/l] [select]
Re^2: regex basics by Anonymous Monk on Feb 04, 2015 at 07:44 UTC
I think you're correct - the ascii art lines (;;;) SHOULD evaluate to TRUE using ($_ !~ /;\s+/). But the art is NOT present in the output (with the latest posted code)	[reply]