I am checking the length of an argv argument, and am wondering if I also need to check it for 0?

Prove your answer by quoting the Standard, POSIX, or some other relevant source.

>Solution :

• It is possible argv to be NULL if argc is zero

Is it possible for an argv[n] argument to have a length of 0

• argv[0] can have a zero length if program name is not provided by the environment. ("argv[0][0] shall be the null character if the program name is not available from the host environment")

C standard:

5.1.2.2.1 Program startup

1. The function called at program startup is named main. The implementation declares no prototype for this
   function. It shall be defined with a return type of int and with no
   parameters: int main(void) { /* … */ } or with two parameters
   (referred to here as argc and argv, though any names may be used, as
   they are local to the function in which they are declared): int
   main(int argc, char argv[]) { / … */ } or equivalent;9) or in some
   other implementation-defined manner.
2. If they are declared, the
   parameters to the main function shall obey the following constraints:

• The value of argc shall be nonnegative.
• argv[argc] shall be a null
  pointer.
• 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 host environment is not capable of
  supplying strings with letters in both uppercase and lowercase, the
  implementation shall ensure that the strings are received in
  lowercase.
• 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. If the value of argc is greater than one, the strings
  pointed to by argv[1] through argv[argc-1] represent the program
  parameters.
• The parameters argc and argv and the strings pointed to
  by the argv array shall be modifiable by the program, and retain their
  last-stored values between program startup and program termination.