[abbeyj]

This can lead to an interesting situation where a program will work if launched by a shell (or by another program that uses `execlp`), but will fail if it is launched with a different variant of `exec`. For example:

    $ touch empty
    $ chmod a+x empty

    $ ./empty  # Works

    $ valgrind -q ./empty  # Works

    $ timeout 10s ./empty  # Works

    $ /usr/bin/time ./empty  # Works

    $ perl -e 'exec("./empty") or die'  # Works

    $ python -c 'import subprocess; subprocess.check_call("./empty", shell=True)'  # Works

    $ python -c 'import subprocess; subprocess.check_call("./empty")'  # Fails
    ...
    OSError: [Errno 8] Exec format error

    $ ruby -e 'exec "./empty"'   # Fails
    -e:1:in `exec': Exec format error - ./empty (Errno::ENOEXEC)
            from -e:1

    $ strace ./empty  # Fails
    execve("./empty", ["./empty"], 0x7fff6639f3a0 /* 84 vars */) = -1 ENOEXEC (Exec format error)
    strace: exec: Exec format error
    +++ exited with 1 +++

It can be quite fun to track down why a program executes successfully and then later fails to execute, with no changes made to the program in between.

[jjnoakes]

I knew this about the programming languages which wrap execution in a shell, but I never knew that execlp/execvp/execvpe handled ENOEXEC internally and wrapped the command in a shell too. TIL!