ourhdr.c /gcc -c ourhdr.c编译得到ourhdr.o

#include <errno.h> /* for definition of errno */
#include <stdarg.h> /* ANSI C header file */
#include "ourhdr.h"

static void err_doit(int, const char *, va_list);
char *pname = NULL; /* caller can set this from argv[0] */

/* Nonfatal error related to a system call.
Print a message and return */

void
err_ret(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
err_doit(1, fmt, ap);
va_end(ap);
return;
}

/* Fatal error related to a system call.
Print a message and terminate. */

void
err_sys(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
err_doit(1, fmt, ap);
va_end(ap);
exit(1);
}

/* Fatal error related to a system call.
Print a message and terminate. */

void
err_dump(const char *fmt, ...)
{
va_list ap;

va_start(ap, fmt);
err_doit(1, fmt, ap);
va_end(ap);
abort(); /* dump core and terminate */
exit(1); /* shouldn't get here */
}

/* Nonfatal error unrelated to a system call.
Print a message and return. */

void
err_msg(const char *fmt, ...)
{
va_list ap;

va_start(ap, fmt);
err_doit(0, fmt, ap);
va_end(ap);
return;
}

/* Fatal error unrelated to a system call.
Print a message and terminate. */

void
err_quit(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
err_doit(0, fmt, ap);
va_end(ap);
exit(1);
}

/* Print a message and return to caller.
Caller specifies "errnoflag". */

static void
err_doit(int errnoflag, const char *fmt, va_list ap)
{
int errno_save;
char buf[MAXLINE];

errno_save = errno; /* value caller might want printed */
vsprintf(buf, fmt, ap);
if (errnoflag)
sprintf (buf+strlen(buf), ": %s", strerror (errno_save));
strcat (buf, "\n");
fflush(stdout); /* in case stdout and stderr are the same */
fputs(buf, stderr);
fflush(NULL); /* flushes all stdio output streams */
return;
}