Using mc-wrapper.sh on a Mac

If you like the nice curses based „Finder“ from the unix world called „Midnight commander“ and would like to use the supplied mc-wrapper.sh-Script, that changes the current working directory to mc’s last selected one, you’re a bit lost on the Mac platform, because it doesn’t work. (I’ve installed mc using the wonderful Homebrew)

Why? Interesting you ask. Let’s look into the mc source code. Specifically, the file lib/vfs/interface.c. In line 916, the function „mc_tmpdir“ is defined:

mc_tmpdir (void)
{
    static char buffer[64];
    static const char *tmpdir = NULL;
    const char *sys_tmp;
    struct passwd *pwd;
    struct stat st;
    const char *error = NULL;

You might have noticed the variable „buffer“ with a size of 64. That’s the character buffer the temporary directory will be squeezed into. Now, let’s look at the Linux platform. Where is a temporary directory located on a Linux operating system? Yes, /tmp. Exactly. And mc designs it temporary directory by using that temporary directory, the prefix „mc-“ and then the currently logged in user.

Mac OS does that differently. Mac OS (since 10.5 that is) holds the temporary files in its /var/folders-directory tree. James Reynolds did a very nice investigation about that directory tree. Basically, it’s just a very long folder name with crypting (random) characters in it. The emphasis here is very long folder name.

Because when you got a long username (like dennis.ploeger for example), 64 bits tend to get really short:

$ echo "${TMPDIR}mc-dennis.ploeger" | wc -c
67

So in my case, mc’s temporary folder ends in „mc-dennis.plo“. This is something, that isn’t taken into account when it comes to mc-wrapper.sh. So, to use that script, add a line after the second line, so it looks like this:

MC_USER=`id | sed 's/[^(]*(//;s/).*//'`
MC_TMP="${TMPDIR-/tmp}/mc-$MC_USER"
MC_PWD_FILE="${MC_TMP:0:63}/mc.pwd.$$"

Now, you can just source it and use it as described in the link above.