Re: [Haskell-beginners] doesFileExist cannot get ~/blah_blah right

On Mon, Apr 08, 2013 at 04:04:22PM -0700, Erlend Hamberg wrote:

On 8 April 2013 15:45, Hong Yang wrote:

...

I got "not exists ..." from

fileExists <- doesFileExist "~/blah_blah" if fileExists then print "exists ..." else print "not exists ..."

using the directory-1.1.0.2 package, when ~/blah_blah does exist.

When you type “~/blah_blah” in your shell, the *shell* will expand “~” to your home directory, so when you pass “~/foo” to a program, that program never sees “~/foo”, but “/home/user/foo”. In other words, “~/blah_blah” probably does *not* exist.

What you probably should do is to find the user's home directory and prepend that to “blah_blah”. You can find a user's homedir by calling `getHomeDirectory` from `System.Directory`:

Prelude System.Directory> homedir <- getHomeDirectory Prelude System.Directory> putStrLn $ homedir ++ "/blah_blah" /Users/ehamberg/blah_blah

Also, since we are discussing portability, it's a much better idea to do homedir "blah_blah" instead of homedir ++ "/blah_blah", since the former will use the correct path separator character for whatever system it is compiled on. -Brent