Question

In any C program, the command line argument argv[0] points to the name used to invoke the program. Is there any circumstance in which it will point to an empty string ""?

An example code snippet for such a case would be a good reference.

Answer 1

It’s implementation defined. §5.1.2.2.1 abridged:

• If the value of argc is greater than zero, the array members argv[0] through
  argv[argc-1] inclusive shall contain pointers to strings, which are given
  implementation-defined values by the host environment prior to program startup. The
  intent is to supply to the program information determined prior to program startup
  from elsewhere in the hosted environment. […]

• If the value of argc is greater than zero, the string pointed to by argv[0]
  represents the program name; argv[0][0] shall be the null character if the
  program name is not available from the host environment. […]

So if argc is greater than zero, it’s quite the intention that argv[0] never be an empty string, but it could happen. (Note that with argc equal to n, argv[0] through argv[n - 1] are never null and always point to a string. The string itself may be empty, though. If n is zero, argv[0] is null.)

In practice, of course, you just need to make sure the platforms your targetting behave as needed.