如何以编程方式获取在Linux机器上登录的用户数? [英] How to programmatically get the number of users logged in on a linux machine?

问题描述

我想知道是否可以以编程方式获得使用C语言在Linux机器上登录的用户数量?我做了一些研究，发现了有关utmp.h的信息，但是由于并非所有程序都使用utmp日志记录，因此我认为它不够准确.在此先感谢任何愿意提供帮助的人.

I was wondering if it was possible to programmatically get the number of users logged in on a Linux machine in C? I did some researching and found out about utmp.h but since not all programs use utmp logging, I did not think it would be accurate enough. Thanks in advance to anyone willing to help.

我对大家没有具体说明表示歉意，但是当我说登录用户时，我指的是任何通过shell登录的人.基本上，当您运行不带命令行参数的who命令时，您会得到什么.

I apologize guys for not being more specific but when I say logged in users, I am referring to any logged in via shell. Basically what you get when you run the who command with no command line arguments.

推荐答案

#include <utmp.h>
#include <err.h>

#define NAME_WIDTH  8

    FILE *ufp;
    int numberOfUsers = 0;
    struct utmp usr;
    ufp = file(_PATH_UTMP);
    while (fread((char *)&usr, sizeof(usr), 1, ufp) == 1) {
    if (*usr.ut_name && *usr.ut_line && *usr.ut_line != '~') {
         numberOfUsers++;
        }
    }

    FILE *file(char *name)
    {
        FILE *ufp;

        if (!(ufp = fopen(name, "r"))) {
            err(1, "%s", name);
        }
        return(ufp);
    }

在与utmp玩了几天之后，我发现了.感谢您的帮助.

After a couple of days playing around with utmp, I figured it out. Thanks for the help guys.

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