Why the message of perror() is "success"?

henry0712 · 12-23-2006, 08:05 PM

hi, everybody:
In a c-program code, using the perror() function:
perror("functionname");
When the function return, the displayed message is:
functionname: Success

I found the explaination in man:
**********************************************
First (if s is not NULL and *s is not NUL) the argument string s is printed, followed by a colon and a blank. Then the message and a new-line.
**********************************************
How can I do know what the message is? When is it "Success" or other message?

thanks!

randyding · 12-23-2006, 08:51 PM

I seems there is some confusion about what perror() does. Also from man, "The perror() function shall map the error number accessed through the symbol errno..."
If errno is 0 then "Success" will be printed after your message.
Is this what you mean?

henry0712 · 12-23-2006, 09:54 PM

Thank randyding, yes, I see it. The message is the status of last function call , isn't it?

jlliagre · 12-23-2006, 10:15 PM

Actually the status of the last function call that failed, and only if that last call is a system or library one.

In the latter case, the library should have set the global variable errno.