Recently I downloaded a source (LevBot) and then I see this line:
} elsif($text =~ /^slaps $levbot_nick/i) {
- But what
/^and/ido? - Why to use they?
I think this is regular expression, I'm right?
views:
268answers:
7
+3
A:
Yes. See the perlre documentation. Briefly, /^ matches the start of a line, and /i means it's case-insensitive.
Brian Agnew
2009-12-09 13:18:47
+3
A:
Thats a regular expression
/^slaps $levbot_nick/i
/^ means starts with (actually ^ alone)
/i means ignore case (i alone after / /)
first and last / slashes are boundary of regex
S.Mark
2009-12-09 13:18:53
+21
A:
/Delimiter denoting start of regex (The char/is not part of the regex)^Matches the start of a line/Delimiter for the end of the regex (not part of the regex)iFlag to make the regex case insensitive
Other flags possible are:
gGlobalsDot matches new line charactersxExtended - ignores whitespaces in the pattern and allows commentsmMultiline mode.
Amarghosh
2009-12-09 13:19:07
Well, the / starts the match operator, not the regex. It's a slight but important difference.
brian d foy
2009-12-09 14:54:43
I don't know Perl and I am not aware of the difference - can you please explain/give a link?
Amarghosh
2009-12-09 15:00:51
The stuff inside the slashes is the actual "regular expression". The slashes merely indicate where the expression starts and stops, but are not a part of the actual expression.
Mark Canlas
2009-12-09 16:11:17
@Amarghosh: the regular expression is the pattern that you're looking to match. The match operator is the syntax that tells the Perl interpreter: here comes a regex. In Perl, the match operator is normally delimited by '/' at start and end, but you can use delimiters (e.g., `m{^foo}`). See the section "Regexp Quote like operators" in perldoc perlop for the gory details. http://perldoc.perl.org/perlop.html#Regexp-Quote-Like-Operators
Telemachus
2009-12-09 16:12:01
That was exactly my understanding - and that's exactly what I meant by `delimiter`
Amarghosh
2009-12-09 16:18:09
Looking at Amarghosh's answer again, though, I'm not sure myself what brian objects to. Amarghosh didn't say that `/` was part of the regular expression; he said it denoted the start of the regex. That seems pretty reasonable to me here.
Telemachus
2009-12-09 16:18:48
@Amarghosh: yeah, I reread your answer and came to that same conclusion. I think "delimiter denoting the start of the regex" is reasonable, but there may be a subtlety I'm missing as well.
Telemachus
2009-12-09 16:19:44
@Telemachus Added clarification anyway.
Amarghosh
2009-12-09 16:20:02
Amarghosh: gsx are not all flags that are allowed. 'e' and 'm' are important.
Alexandr Ciornii
2009-12-09 17:40:22
i, m, s, x, and the mostly-useless o to control matching; c, e, and g to control substitution (hey, that's a C major chord!)
hobbs
2009-12-09 23:37:46
+4
A:
Yes, this is a regular expression.
- The
/on either side mark the pattern's beginning and end. - The
^at the start of the patten means "only match this at the beginning of the string, and nowhere else." - The
iafter the end of the pattern is a modifier, it means "be case-insensitive when matching this", since the default is case-sensitive.
Adam Bellaire
2009-12-09 13:19:31
+2
A:
/^ matches the beginning of a line.
/i means case insensitive search.
Tim S. Van Haren
2009-12-09 13:21:17
A:
This syntax in Perl was inspired by awk's /xxx/ Pattern matching feature.
Jim Dennis
2009-12-10 05:03:57