Kragen's err.h

They were useful little functions -- things I'd written myself more than once, usually under a different name, because they're very useful. So, instead of looking for some source code on the Net for them, I just quickly rewrote them myself.

Here's release 1.

Briefly, they're sort of like a C equivalent of the warn() and die() functions in Perl.

The original BSD versions print the program's name followed by a colon before anything else. Unfortunately, there's no portable way to do this, so these quick-and-dirty substitutes just print their own names.

All of them print newlines at the ends of their messages.

• void err(int eval, const char * fmt, ...) passes 'fmt' and the ... arguments to fprintf(stderr), prints an error corresponding to the current value of errno, and exits with 'eval'. This is very useful! Example:

  	if ((fd = open(fname, O_RDONLY)) == -1) err(1, "open: %s", fname);
  	

  might print:

  	verr: open: example.c: No such file or directory
  	

  and make the program exit() with exit value 1.
• void verr(int eval, const char * fmt, va_list args) is the va_list version of err().
• void errx(int eval, const char * fmt, ...) is just like err(), but it doesn't print the error corresponding to errno. Example:

  	if ((x = malloc(size)) == NULL) errx(-1, "malloc(%d): no memory", size);
  	

  might print:

  	verrx: malloc(2048): no memory
  	

  and make the program exit() with exit value -1.
• void verrx(int eval, const char * fmt, va_list args) is the va_list version of errx().
• void warn(const char * fmt, ...) is the same as err(), except that it doesn't make the program exit().
• void vwarn(const char * fmt, va_list args) is the va_list version of warn().
• void warnx(const char * fmt, ...) is the same as errx(), except that it doesn't make the program exit().
• void vwarnx(const char * fmt, va_list args) is the va_list version of warnx().