错误：perror 和 fprintf 之间的区别

Question

Any difference between the following two approaches when encountering and error?

if (!mallocd_buffer) {

    // this?
    fprintf(stderr,"malloc() failed in file %s at line # %d", __FILE__, __LINE__);

    // or this?
    perror("Failed to copy a string\n\n\n\n\n");

    exit(EXIT_FAILURE);
}

Answer 1

Using perror , you get the system error message implied by the current value of errno in the output, after the string you supply as the argument.

Using fprintf(stderr, "…", …) , you're in complete control of the formatting.

I rarely use perror() ; it doesn't meet my requirements as formatting the string to pass to it is fiddly. I use the functions I wrote such as err_syserr() — code which is available in my SOQ (Stack Overflow Questions) repository on GitHub as files stderr.c and stderr.h in the src/libsoq sub-directory.

On BSD, there is a similar package called err(3) ; you can find it on Linux too (see err(3) ). You will probably prefer to use that over my code, if only because the system functions manage to be privy to the value of argv[0] indirectly, whereas my code isn't because there isn't a portable interface to gain access to argv[0] except via the arguments to main() ) and my code therefore relies on you calling err_setarg0(argv[0]) in main() to set the program name.