Close a file
Integer_Type fclose (File_Type fp)
The fclose function may be used to close an open file pointer
fp. Upon success it returns zero, and upon failure it sets
errno and returns -1. Failure usually indicates a that
the file system is full or that fp does not refer to an open file.
Many C programmers call fclose without checking the return
value. The S-lang language requires the programmer to explicitly
handle any value returned by a S-lang function. The simplest way to
handle the return value from fclose is to use it as:
() = fclose (fp);
fopen, fgets, fflush, errno