pattern matching

himanshu.padmanabhi has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: pattern matching by toolic (Bishop) on Mar 04, 2009 at 14:58 UTC
To remove trailing "^@", you could use the substitution operator: `use strict; use warnings; while (my $str = <DATA>) { chomp $str; $str =~ s/\^\@$//; print "$str\n"; } __DATA__ himanshu.txt^@ himanshu-prg.txt^@ hel_llo-workd.txt^@ foo` [download] prints: `himanshu.txt himanshu-prg.txt hel_llo-workd.txt foo` [download]	[reply] [d/l] [select]
Re^2: pattern matching by Anonymous Monk on Mar 04, 2009 at 15:02 UTC
Probably he wants `=~ s/[^\w.]*$//;` because `$ perl -le print(chr(0)) \|cat -v ^@` [download]	[reply] [d/l] [select]
Re: pattern matching by shmem (Chancellor) on Mar 04, 2009 at 15:44 UTC
That should be `$str="himanshu.txt^@"; if($str =~ /(\w+)\.(\w+)/) { $str = "$1.$2"; }` [download] What is your "^@" ? That looks like an ASCII 0, as less(1) would show it. You can sense that and remove it with `if ($str =~ s/\0$//) { print "found NUL byte at the end of '$str'\n"; }` [download]	[reply] [d/l] [select]
Re: pattern matching by cdarke (Prior) on Mar 04, 2009 at 14:56 UTC
TMTOWTDI: you could use chomp instead: `{ local $/ = "^@"; chomp $str; }` [download]	[reply] [d/l]
Re^2: pattern matching by himanshu.padmanabhi (Acolyte) on Mar 04, 2009 at 15:01 UTC
Thank you very much. You already given me this solution. It is working well. I should have try it that time only.:(	[reply]
Re: pattern matching by AnomalousMonk (Archbishop) on Mar 04, 2009 at 15:22 UTC
What is `"^@"`? If it is a Control-@ (ASCII null) character, then `$string =~ s{ \c@ \z }{}xms;` will do the trick. If there may be more than one, use `$string =~ s{ \c@ + \z }{}xms;` `>perl -wMstrict -le "my $string = qq{ab.cd\c@}; print qq{'$string'}; $string =~ s{ \c@ \z }{}xms; print qq{'$string'}; " 'ab.cd ' 'ab.cd' >perl -wMstrict -le "my $string = qq{ab.cd\c@\c@\c@}; print qq{'$string'}; $string =~ s{ \c@ + \z }{}xms; print qq{'$string'}; " 'ab.cd ' 'ab.cd'` [download]	[reply] [d/l] [select]
Re: pattern matching by GrandFather (Saint) on Mar 04, 2009 at 22:23 UTC
Always use strictures (use strict; use warnings;). That code should have generated the warning: `Use of uninitialized value in concatenation (.) or string at ...` [download] True laziness is hard work	[reply] [d/l]
Re: pattern matching by Anonymous Monk on Mar 04, 2009 at 14:50 UTC
This is working well.So I am getting $str="himanshu.txt" Not possible, $2 is always undefined. `#!/usr/bin/perl -- use strict; use warnings; my $str="himanshu.txt^@"; if($str =~ /(\w+)/) { $str = "$1.$2"; } print "$str\n" __END__ Use of uninitialized value in concatenation (.) or string at - line 6. himanshu.` [download] What will the regular expression? `use re 'debug';` to see, ex #!/usr/bin/perl -- use strict; use warnings; use re 'debug'; my $str="himanshu.txt^@"; if($str =~ /(\w+)/) { $str = "$1.$2"; } print "$str\n" __END__ Compiling REx `(\w+)' size 7 Got 60 bytes for offset annotations. first at 4 1: OPEN1(3) 3: PLUS(5) 4: ALNUM(0) 5: CLOSE1(7) 7: END(0) stclass "ALNUM" plus minlen 1 Offsets: [7] 1[1] 0[0] 4[1] 2[2] 5[1] 0[0] 6[0] Matching REx "(\w+)" against "himanshu.txt^@" Matching stclass "ALNUM" against "himanshu.txt^@" Setting an EVAL scope, savestack=5 0 <> <himanshu.txt> \| 1: OPEN1 0 <> <himanshu.txt> \| 3: PLUS ALNUM can match 8 times out of 2147483647.. +. Setting an EVAL scope, savestack=5 8 <manshu> <.txt^@> \| 5: CLOSE1 8 <manshu> <.txt^@> \| 7: END Match successful! Use of uninitialized value in concatenation (.) or string at test.pl l +ine 7. himanshu. Freeing REx: `"(\\w+)"' [download]	[reply] [d/l] [select]