Is `argv[0]` Always the Executable Name in C/C ?

Is argv[0] Always the Executable Name, or a Mere Convention?

When supplying arguments to the main() function in C or C applications, the question arises: does argv[0] invariably represent the name of the executable? Or is this merely a widespread convention, with no guarantee of universal applicability?

Delving into the Standards

To ascertain the true nature of argv[0}, we must consult the relevant standards. ISO C11 explicitly states that when argc exceeds zero, "argv[0] represents the program name." However, it crucially adds that "argv[0][0] shall be the null character if the program name is not available from the host environment."

This clarification reveals that argv[0] only embodies the program name if it's readily obtainable from the host environment. Furthermore, the standard emphasizes that the values contained in argv are entirely implementation-defined, subject to the whim of the host environment.

Implications for Program Names

Consequently, the program name might be blank if the host environment lacks the ability to provide it, or it could take on any arbitrary form if it is accessible. In theory, the host environment could even opt to provide a gibberish program name for its amusement!

Cautionary Considerations

Yet, it's imperative to note that "implementation-defined" has a distinct connotation within ISO standards. Implementations are obligated to document their specific behavior in detail. Consequently, even platforms like UNIX, notorious for their flexibility in populating argv[0] with arbitrary content through the exec family of commands, must officially record their practices.

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