关于who命令的c语言实现问题（带缓冲）
带缓冲的who2.c 代码如下：/*
*we add a buffer area in who2.c.
*/
#include <stdio.h>
#include <utmp.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <time.h>
/*#define SHOWHOST*/ //include remote machine on output
//-------------------------------------------------------------------------
#define NRECS 16
#define NULLUT ((struct utmp *)NULL)
#define UTSIZE (sizeof(struct utmp))
static char utmpbuf; //storage
static intnum_recs; //num stored
static intcur_rec; //next to go
static intfd_utmp = -1; //read from
int utmp_open(char *filename)
{
fd_utmp = open(filename, O_RDONLY);
cur_rec = num_recs = 0;
return fd_utmp;
}
int utmp_reload()
{
int amt_read;
amt_read = read(fd_utmp, utmpbuf, NRECS * UTSIZE);
num_recs = amt_read/UTSIZE; //how many did we get?
cur_rec = 0; //reset pointer
return num_recs;
}
struct utmp * utmp_next()
{
struct utmp * recp;
if( fd_utmp == -1)
return NULLUT;
if(cur_rec == num_recs && utmp_reload() == 0) //这段不是很明白， return NULLUT;
recp = (struct utmp *) &utmpbuf; ]//这只是取得缓冲中的一个(struct utmp *)结构数据吧，
//之后就调用show_info();显示出此条信息了吧，那如何实现依次读取并显示出buff中的所有信息的？感觉是读满一个buff后只显示了
//一条就又去read了，应该不是这样吧，请高手指点，多谢！！！！！ cur_rec++;
return recp;
}
void utmp_close()
{
if(fd_utmp != -1)
close(fd_utmp);//don't close if not open
}
//-------------------------------------------------------------------------
void show_info(struct utmp *);
void showtime(long timeval);
int main()
{
struct utmp * utbufp; //holds pointer to next rec
struct utmp * utmp_next();//return pointer to next
if(utmp_open(UTMP_FILE) == -1)
{
perror(UTMP_FILE);
exit(1);
}
while ( (utbufp = utmp_next() ) != ((struct utmp *) NULL) )
show_info(utbufp);
utmp_close();
return 0;
}
/*
* display contents of the utmp struct
*/
void show_info( struct utmp * utbufp)
{
/*
* remove the blank record
*the entry ut_type in struct utmp indicate the types
* USER_PROCESS is the auser process
*/
/* if(utbufp-> ut_type != USER_PROCESS)
return;*/
printf("% -8.8s", utbufp->ut_name);
printf(" ");
printf("% -12.12s", utbufp->ut_line);
printf(" ");
//printf("%101d", utbufp->ut_time);
showtime(utbufp->ut_time);
printf(" ");
#ifdef SHOWHOST
printf("(%s)", utbufp->ut_host);
#endif
printf("\n");
}
void showtime(long timeval)
{
/*
* display time
*/
char *cp;
cp = ctime(&timeval);
printf("%12.12s", cp+4);
} :cry: 怎么没人回答啊？？？？？
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