who knew path joining differed so between Python, Ruby, Node, Perl
In Python I do a lot of path manipulations for build systems, various
command-line utilities and Komodo support modules. Typically this is with
Python’s os.path module. One thing I’ve come to expect of path joining,
os.path.join, is this (apparently rare) detail:
If any component is an absolute path, all previous path components
will be discarded.
I say “apparently rare” because, in Python:
$ python
>>> import os.path
>>> os.path.join("/Users/trentm", "/var/log")
'/var/log'
in Ruby:
$ irb
>> File.join("/Users/trentm", "/var/log")
=> "/Users/trentm/var/log"
in Node.js:
$ node
node> var path = require('path')
node> path.join("/Users/trentm", "/var/log")
'/Users/trentm/var/log'
in Perl:
$ cat pathjoin.pl
use File::Spec;
print File::Spec->join('/Users/trentm', '/var/log'), "\n";
$ perl pathjoin.pl
/Users/trentm//var/log
Conclusions? Certainly none of these libraries is going to change their
behaviour here, with the possible exception of Node which is young and
changing very quickly. I’d say the double ‘/’ in Perl’s File::Spec is
poor – though it doesn’t give in invalid path. You could certainly argue
that Ruby’s and Node’s interpretation is less subtle (often a good thing).
I like Python’s interpretation: os.path.join is kind of like
running cd for each given path in sequence to get the resultant
directory. It means I don’t need a guard against an absolute path input
datum being joined to a current working directory scope.
I’d be curious to know what is typical in other languages, if there are any takers reading this post. If blog commenting isn’t your thing, you can tweet “@trentmick”.