Re: Single Quotes - how to avoid any escape processing?

Although this is an old thread I think it aligns well with a current issue I have whilst processing Windows paths. I have spent the last hour scouring THE WEB and can't for the life of me find a clean solution to my issue. Basically what I want to do is split a path into a list of each sub directory, so in its simplest form I tried the following...

$PathOnly = "c:\Dir1\Dir2\Dir3";

@SubDirs = split('\', $PathOnly);
[download]

This doesn't work since the \' gets escaped and I end up effectively with a missing ' So, tried to escape the \ with the following...

@SubDirs = split('\\', $PathOnly);
[download]

But that also has an error "trailing \ in regex" As does the following...

@SubDirs = split("\\", $PathOnly);
[download]

I even tried the following...

my $SplitAt = "\\";
my @SubDirs = split($SplitAt, $PathOnly);
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Whilst this doesn't have syntax errors, and $SplitAt seems to get theexpected "\" it fails on the execution of the split with the same "trailing \ in regex", just at execution time this time. Now... just for kicks and giggles I tried the following...

my $SplitAt = "\\\\";
my @SubDirs = split($SplitAt, $PathOnly);
[download]

BOOM !!! I get the correct result (I actually thought of this whilst typing the comment but figured the info might help someone at some point in time) So, then I tried the following...

my @SubDirs = split("\\\\", $PathOnly);
[download]

This also worked as I wanted. So, my original question has changed from "How do I split a Windows path on \ ?" to "Why does "\\\\" work in the split statement? I have been working with Perl on and off for about 20 years but I am by no means an expert, but this conundrum completely confuses me. BR, Steve

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Re^2: Single Quotes - how to avoid any escape processing? by Corion (Patriarch) on Aug 25, 2019 at 18:25 UTC
split does not take a string as its first argument, it takes a regular expression. So the correct usage is `@SubDirs = split(/\\/, $PathOnly);` [download] But maybe you want to use File::Spec instead, or Path::Tiny? `my @SubDirs = File::Spec->splitdir( $PathOnly );` [download]	[reply] [d/l] [select]
Re^2: Single Quotes - how to avoid any escape processing? by AnomalousMonk (Archbishop) on Aug 25, 2019 at 18:38 UTC
Either of the literals `"\\\\"` or `'\\\\'` interpolate in a `m//` or `qr//` operator to a pair of backslash characters `\\` (escaped-backslash) which match a single backslash character. `c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le "print '\\'; print '\\\\'; print qq{\\}; print qq{\\\\}; ;; print qr{\\}; my $bb = '\\\\'; print qr{$bb}; ;; my $PathOnly = 'c:\Dir1\Dir2\Dir3'; ;; my @SubDirs = split(m/\\/, $PathOnly); dd \@SubDirs; ;; @SubDirs = split($bb, $PathOnly); dd \@SubDirs; " \ \\ \ \\ (?-xism:\\) (?-xism:\\) ["c:", "Dir1", "Dir2", "Dir3"] ["c:", "Dir1", "Dir2", "Dir3"]` [download] Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re^2: Single Quotes - how to avoid any escape processing? by soonix (Canon) on Aug 25, 2019 at 18:37 UTC
Corion already commented on the problem you noted, but there's another: your $PathOnly is in double quotes, so the backslashes there are interpreted as escape sequences. Also, should you ever be in need of a string consisting of a single backslash, you could use `"\N{REVERSE SOLIDUS}"` (prior to v5.16, you have to `use charnames` explicitly for this to work). That is complicated, but whoever reads that, will have no doubt that you indeed want a single backslash that is not part of an escape secuence.	[reply] [d/l] [select]
Re^3: Single Quotes - how to avoid any escape processing? by AnomalousMonk (Archbishop) on Aug 25, 2019 at 18:54 UTC
`... your $PathOnly is in double quotes, so the backslashes there are i +nterpreted as escape sequences.` [download] SteveDC: Ah, yes! `c:\@Work\Perl\monks>perl -wMstrict -le "my $PathOnly = qq{c:\Dir1\Dir2\taint_so}; print qq{>$PathOnly<}; " Unrecognized escape \D passed through at -e line 1. Unrecognized escape \D passed through at -e line 1. >c:Dir1Dir2 aint_so<` [download] Don't know how you missed the warnings. You do have warnings enabled, right? Right? Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]


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