#include "apue.h"
#include <errno.h>        /* for definition of errno */
#include <stdarg.h>       /* ISO C variable aruments */static void    err_doit(int, int, const char *, va_list);/** 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, errno, fmt, ap);va_end(ap);
}/** 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, errno, fmt, ap);va_end(ap);exit(1);
}/** Fatal error unrelated to a system call.* Error code passed as explict parameter.* Print a message and terminate.*/
void
err_exit(int error, const char *fmt, ...)
{va_list        ap;va_start(ap, fmt);err_doit(1, error, fmt, ap);va_end(ap);exit(1);
}/** Fatal error related to a system call.* Print a message, dump core, and terminate.*/
void
err_dump(const char *fmt, ...)
{va_list        ap;va_start(ap, fmt);err_doit(1, errno, 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, 0, fmt, ap);va_end(ap);
}/** 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, 0, fmt, ap);va_end(ap);exit(1);
}/** Print a message and return to caller.* Caller specifies "errnoflag".*/
static void
err_doit(int errnoflag, int error, const char *fmt, va_list ap)
{char   buf[MAXLINE];vsnprintf(buf, MAXLINE, fmt, ap);if (errnoflag)snprintf(buf+strlen(buf), MAXLINE-strlen(buf), ": %s",strerror(error));strcat(buf, "\n");fflush(stdout);       /* in case stdout and stderr are the same */fputs(buf, stderr);fflush(NULL);        /* flushes all stdio output streams */
}

#include <stdio.h>int printf(const char *format, ...);　　　　　　　　　　　　　　  //格式化到标准输出
int fprintf(FILE *stream, const char *format, ...);　　　　    //格式化到文件
int sprintf(char *str, const char *format, ...);　　　　　　　　//格式化到字符串
int snprintf(char *str, size_t size, const char *format, ...);//规定了格式化字符串的最大长度#include <stdarg.h>int vprintf(const char *format, va_list ap);
int vfprintf(FILE *stream, const char *format, va_list ap);
int vsprintf(char *str, const char *format, va_list ap);
int vsnprintf(char *str, size_t size, const char *format, va_list ap);

#include <stdarg.h>void va_start(va_list ap, last);type va_arg(va_list ap, type);void va_end(va_list ap);void va_copy(va_list dest, va_list src);

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>int test(char *fmt, ...);int main(int argc, const char *argv[])
{test("test", "hello", "world","");return 0;
}int test(char *fmt, ...){va_list ap;char *temp;va_start(ap, fmt);while(1){temp = va_arg(ap, char *);if(temp != ""){printf("%s ", temp);}elsebreak;}va_end(ap);return 0;
}

#define va_start(ap, v) (ap = (va_list)&v + _INTSIZEOF(v) )#define va_arg(ap,t) (*(t *)( (ap += _INTSIZEOF(t)) - _INTSIZEOF(t) )#define va_end(ap) (ap = (va_list)0)