Advanced UNIX Programming

Determining Success or Failure

When a C function is called, the programmer is interested in two things upon its return:

• Did the function call succeed?

• If not, why did the call fail?

General Rules for Error Indication

The UNIX convention used by most system calls and library functions is that the return value indicates a general success or failure. Return values fall into two major categories:

• The return value is an integer value (int or long). Normally failure is indicated by a value of negative one (-1).

• The return value is a pointer type, such as pointers (char *), (void *) or a pointer to a structure. Failure is indicated by a null return pointer and success by a non-null pointer.

Exceptions to the General Rule

There are exceptions to the general ...