add a character at the end of a string

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

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Re: add a character at the end of a string by reasonablekeith (Deacon) on Dec 13, 2005 at 11:27 UTC
I always do it like this... `$string =~ s\|/?$\|/\|;` [download] although there are countless other ways. This one works by matching a trailing slash (if there is one) and 'replacing' it with a new trailing slash. an alternative would be as follows.. `$string .= '/' if $string !~ m\|/$\|;` [download] --- my name's not Keith, and I'm not reasonable.	[reply] [d/l] [select]
Re^2: add a character at the end of a string by rsennat (Beadle) on Dec 13, 2005 at 11:37 UTC
If I am right, /?$ means, the last slash in the string is replaced with /. can you get me any links or nodes here to read more on perl substitution operator. Thanks rsennat	[reply]
Re^3: add a character at the end of a string by reasonablekeith (Deacon) on Dec 13, 2005 at 11:49 UTC
ok, here goes... the / means just that, match a forward slash the ? then says that you don't have to match the preceding character, but it will try to if it's there Finally the $ ties the match to the very end of the string So, if your string ends with a / it will be matched, and replaced with another slash, with no net effect. However, if your script doesn't end with a slash, the whole substitution still matches because the slash was optional. In this case all we're matching is the 'end' of the string. The substitution then replaces this (zero-width) match with the new slash, which has the net effect in inserting the trailing slash. for futher reading I’d recommend ‘perldoc perlre’ and the excellent “Mastering Regular Expressions” published by O’Reilly (which is superb) --- my name's not Keith, and I'm not reasonable.	[reply]
Re: add a character at the end of a string by Tomte (Priest) on Dec 13, 2005 at 11:40 UTC
I guess there are alternatives, but it works: `# can't be called with a literal string as arg # but that wasn't asked for :) sub appendMissingSlash { return $_[0] .= substr($_[0], -1) eq "/" ? "" : "/"; } my $string = "/tmp/check"; appendMissingSlash($string); print $string,"\n"; __END__ /tmp/check/` [download] Update: I didn't use a regex, as other examples given suggest, because we know the position and the character to check for, using the regex engine seemed overkill to me regards, tomte An intellectual is someone whose mind watches itself. -- Albert Camus	[reply] [d/l]
Re^2: add a character at the end of a string by jhourcle (Prior) on Dec 13, 2005 at 12:18 UTC
I didn't use a regex, as other examples given suggest, because we know the position and the character to check for, using the regex engine seemed overkill to me I this case, it's a fixed length string, at the end of the string, so it's a rather efficient match with regex -- if you were really concerned with speed, you'd have not wanted to append an empty string when you didn't have to: Read more... (3 kB) In my opinion, it's a case of premature optimization, as with the differences so insignificant for the top three, it's not worth worrying about. (multiple runs don't have a consistent leader, and variations in versions of perl might cause different results) ... and odds are, this one replacement is a very small part of the overall program, so I wouldn't even be opposed to the slowest one, as it's the shortest to type.	[reply] [d/l] [select]
Re^3: add a character at the end of a string by Tomte (Priest) on Dec 13, 2005 at 13:17 UTC
In my opinion, it's a case of premature optimization, In mine, it's a case of using the right tool for the job, not contradicted (again IMO) by the benchmark results :) regards, tomte An intellectual is someone whose mind watches itself. -- Albert Camus	[reply]
Re: add a character at the end of a string by kulls (Hermit) on Dec 13, 2005 at 11:32 UTC
I tried little bit here, `$string.="/" if(not $string =~/\/$/ );` [download] kulls	[reply] [d/l]
Re: add a character at the end of a string by ikegami (Patriarch) on Dec 13, 2005 at 15:30 UTC
The portable way would be to use core module File::Spec's `catpath` to join the dir to the filename instead of playing with slashes.	[reply] [d/l] [select]