getting the tail of a string

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

Replies are listed 'Best First'.
Re: getting the tail of a string by Zaxo (Archbishop) on Jun 10, 2003 at 15:32 UTC
`use File::Basename;` After Compline, Zaxo	[reply] [d/l]
Re: getting the tail of a string by adrianh (Chancellor) on Jun 10, 2003 at 15:32 UTC
`use File::Basename; my $file_name = basename($full_path);` [download]	[reply] [d/l]
Re: Re: getting the tail of a string by sauoq (Abbot) on Jun 10, 2003 at 19:31 UTC
As he is asking for a way to do this on the command line, I'd be inclined to offer something simple: `my $m = $x =~ m!([^/]*)$!;` [download] -sauoq "My two cents aren't worth a dime.";	[reply] [d/l]
Re^3: getting the tail of a string by adrianh (Chancellor) on Jun 10, 2003 at 20:43 UTC
And I'd be inclined to offer something that worked on my Mac OS 9 box (it's still there buzzing away in the corner :-) To-may-to. Toe-mah-to.	[reply]
Re: getting the tail of a string by TomDLux (Vicar) on Jun 10, 2003 at 15:54 UTC
The correct solution in this case is using basename, since it is a filepath problem. More generally, it's a split() problem. Only most generally is regexp appropriate. Even then, I would avoid POSTMATCH - while the expense is tolerable, it's still high. Better to actually match the string you want, and remember that. `$x =~ m\|(?:[^/]/)/(.)}; print $1;` [download] -- `TTTATCGGTCGTTATATAGATGTTTGCA`	[reply] [d/l]
Re:x2 getting the tail of a string (substr and rindex) by grinder (Bishop) on Jun 10, 2003 at 17:11 UTC
I wouldn't say that split and or regexp are the most general ways of attacking this problem. The most general (read: efficient) way would be to find the character with rindex and extract the end of the string with substr. The following does the trick: `my $ext = substr($x, rindex($x,'.')+1);` This happens to rely on a side-effect of rindex, which is that if the character sought for is not found in the string, -1 is returned. Add 1 (pedant note: `length('.')` in fact), and instead of stepping over the sought character, it brings -1 up to 0, and hence your substr will hand you back the whole string. This can be construed as a feature :) But yes, File::Basename is the way to go in this particular case. update: weird transcription error spotted by sauoq: I had `-rindex` instead of `rindex`. Curiously enough, that's exactly what I had when I checked the snippet out on the command line. That'll teach me not to cut and paste... _____________________________________________ Come to YAPC::Europe 2003 in Paris, 23-25 July 2003.	[reply] [d/l]
Re: getting the tail of a string (fun with command line quotes.) by sauoq (Abbot) on Jun 10, 2003 at 19:52 UTC
Unfortunately i can not use $POSTMATCHs shortform $' on command line. Sure you can. You just have to be a little more creative about how you get it in there. The way to do it is to end the single quoted portion of the command line, put another single quote but escape it, and continue on if necessary with another single quote. with the example you gave, that would be: `perl -we '$x="j::/tmp/lz/ncak.030610.141654";$x=~/.+\// && print $'\'` [download] A shorter example for illustration: `perl -le '$_="abc";/b/;print $'\' \| ^--- the single quote part of $' +--- the dollar part of $'` [download] And to illustrate putting more after that... `perl -le '$_="abc";/b/;print $'\'';print "more"'` [download] -sauoq "My two cents aren't worth a dime.";	[reply] [d/l] [select]
Re: getting the tail of a string by DrHyde (Prior) on Jun 10, 2003 at 18:53 UTC
Whilst others are correct in pointing out that the best perl solution for the task at hand involves basename, those suggestions don't point out what your problem here is - which will bite you in the arse whenever you try to use $' and similar on the command line. That is, you need to understand the black art of shell quoting. This: `perl -we '$x="/foo/bar/ncak.030610.141654";$x=~/.+\// && print $'\'` [download] works, at least with the bash installed on this 'ere OS X box. What it does is single-quote all your perl up to and including the last $. It then ends the single-quoting, and immediately - with no intervening space - provides a single-quote. The single-quote is escaped so that the shell doesn't try to start a new quoted string and complain when it can't find the closing delimiter.	[reply] [d/l]


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