编写who命令

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Refer:编写who命令

#include<stdio.h>#include<utmp.h>#include<string.h>#include<stdlib.h>#include<time.h>#define SHOWHOSTvoid show_info(struct utmp*);int main(){    struct utmp record;    FILE *fp;    int strulen=sizeof(record);    if((fp=fopen("/var/run/utmp","r"))==0){ //打开文件        perror("fopen");        exit(0);    }    memset(&record,0x00,strulen);    while(fread(&record,strulen,1,fp)){ //循环读取记录（结构体）        show_info(&record);    }    fclose(fp); //关闭文件    return 0;}void show_info(struct utmp *buf){    if(buf->ut_type!=USER_PROCESS) //非登录用户        return;    printf("%-8s ",buf->ut_name); //输出用户名    printf("%-12s ",buf->ut_line); //终端设备名    time_t timelong=buf->ut_time;    struct tm *localnow=localtime(&timelong);    printf("%04d-%02d-%02d %02d:%02d ",localnow->tm_year+1900,localnow->tm_mon+1,localnow->tm_mday,localnow->tm_hour,localnow->tm_min); //登录时间    #ifdef SHOWHOST        printf("(%s)",buf->ut_host);    #endif    printf("\n");}

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