HP C/iX Library Reference Manual (30026-90004)

Chapter 5 165

HP C/iX Library Function Descriptions

fprintf

}

file = fopen(argv[1], "r");

if(file == NULL) {

fprintf(stderr, "Can't open %s.\n", argv[1]);

exit(1);

}

while(fscanf(file, "%*s") != EOF)

count;

fprintf(stdout, "Number of words found: %d\n", count);

exit(0);

}

This program counts the number of "words" in the ﬁle speciﬁed as its only argument. A

word is deﬁned as a string of nonspace characters.

In this program, fprintf() directs error messages to stderr. Error output is written on a

different stream than normal output; the error output (or the normal output) can be

redirected to another destination. For example, invoking the program with stderr set to

the ﬁle errmsgs causes all output from erroneous conditions to be collected in the errmsgs

ﬁle. In this example, this capability is trivial because the program terminates on any error.

However, this is a very useful capability for programs that output any number of warnings

without terminating. Not only does this command keep the desired output uncluttered

with error messages, but it also enables you to save the output. Thus, it is good

programming practice to write error messages and warnings on stderr and to use stdout

(or any destination ﬁle) to output normal data.