Simple file locking wrapper command in C

A simple command that wraps another command, locking a file first. It is similar to flock, just simpler.

#include 
#include 
#include 
#include 
#include 
#include 

void attemptLock(const char *lockFileName)
{
    int fd = open(lockFileName, O_CREAT | O_WRONLY, 0666);
    if (!fd || flock(fd, LOCK_EX))
        warn("Cannot lock %s", lockFileName);
}

int main(int argc, char *argv[])
{
    if (argc < 3)
        errx(EXIT_FAILURE, "Not enough arguments.\nUsage: %s LOCKFILENAME COMMAND...\n", argv[0]);
    attemptLock(argv[1]);
    argv += 2;  // Skip our own command name and LOCKFILENAME.
    execvp(argv[0], argv);
    err(EXIT_FAILURE, "Cannot execute %s", argv[0]);
}

Anything fishy? Bogus? Wrong? Anything that can be improved (besides adding options like -h)?

Besides reinventing the wheel the things I'm concerned about are:

• the warn in attemptLock, because if either creating the lock file

fails, or if you can't get the lock (or the call was interrupted), I
would expect the wrapper to exit instead,

• the return value of open, which might very well be negative, so just

check for that separately and give an error message for that,

• the return value of flock, where you should handle EINTR in a loop

I believe?

StackExchange Code Review Q#80227, answer score: 2