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

[Erlend Hamberg]

On 8 April 2013 15:45, Hong Yang <hyangfji at gmail.com> 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

-- 
Erlend Hamberg
ehamberg at gmail.com
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