I am attempting to translate a possibly relative path to an absolute path. I need to correctly collapse . and .. if it appears in the path I am given.

I have toyed with this an awful lot today and I arrived at something like: 

# NOTE: I have already prepended pwd if needed

#remove .
while( $path =~ m#/\./# ) {
    $path =~ s#/\.#/#;
}

# remove ..
while( $path =~ m#/[^/]+?/\.\./# ) {
    $path =~ s#/[^/]+?/\.\.#/#;
}

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This was not satisfying - the m## and then an s### with exactly the same arguments was lacking. Remembering that s### returns true if something was replaced, I was able to reduce this to 
#remove .
while ( $path =~ s#/\./#/# ) {;}

#remove ..
while ( $path =~ s#/[^/]+?/\.\./#/# ) {;}

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But this still does not please me. Using two loops when I feel I should only have to use one. Working a bit harder and unleashing the marvelous /e modifier, I was able to finally say 
while ( $path =~ s#(/[^/]+)?/\.(\.)?/defined($2) ? "/" : "$1/"/e ) {;}

[download]
I am pleased but wonder what other ways the honored Monks have found to do this - my solution is likely to be a real CPU pig.

For reasons I cannot elucidate, this solution is right out 

unless ( chdir $path ) {
  die "Couldn't there ($path) from here\n";
}
return `pwd`;

[download]
To further the discussion, I will point out that using the /g modifier does not work - the regex engine does double quotish expansion only once and will not reapply the regex to the new string. A wise move, considering the evil deep recursions that could result.

Mik
Mik Firestone (perlus bigotous maximus )

In reply to Normalized directory paths by mikfire

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