linux常用函数记录

本文转自:
https://blog.csdn.net/qq_29344757/article/details/80004483
https://blog.csdn.net/qq_29344757/article/details/80004746

一、获取/设置Linux系统的网络信息

1.获取IP地址、子网掩码地址、Mac地址、广播地址

#include <stdio.h>
#include <string.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>
#include <errno.h>

int GetNetworkInfo(void)
{
    int fd;
    int interfaceNum = 0;
    struct ifreq buf[16];
    struct ifconf ifc;
    struct ifreq ifrcopy;
    char mac[32] = {0};
    char ip[32] = {0};
    char broadAddr[32] = {0};
    char subnetMask[32] = {0};

    if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    {
        perror("socket");
        close(fd);
        return -1;
    }

    ifc.ifc_len = sizeof(buf);
    ifc.ifc_buf = (caddr_t)buf;
    /* 执行完这句后ifc.ifc_len已经不一定就等于sizeof(buf)，而是小于或等于sizeof(buf)，取决于网卡的个数 */

    if (!ioctl(fd, SIOCGIFCONF, (char *)&ifc))
    {
        interfaceNum = ifc.ifc_len / sizeof(struct ifreq);
        while (interfaceNum-- > 0)
        {             
            ifrcopy = buf[interfaceNum];
            if (ioctl(fd, SIOCGIFFLAGS, &ifrcopy))
            {
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
                close(fd);
                return -1;
            }

            //获取IP地址
            if (!ioctl(fd, SIOCGIFADDR, (char *)&buf[interfaceNum]))
            {
                snprintf(ip, sizeof(ip), "%s",
                            (char *)inet_ntoa(((struct sockaddr_in *)&(buf[interfaceNum].ifr_addr))->sin_addr));
                printf("device ip: %s\n", ip);
            }
            else
            {
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
                close(fd);
                return -1;
            }
            //获取子网掩码地址
            if (!ioctl(fd, SIOCGIFNETMASK, &buf[interfaceNum]))
            {
                snprintf(subnetMask, sizeof(subnetMask), "%s",
                            (char *)inet_ntoa(((struct sockaddr_in *)&(buf[interfaceNum].ifr_netmask))->sin_addr));
                printf("device subnetMask: %s\n", subnetMask);
            }
            else
            {
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
                close(fd);
                return -1;
            }
            //获取mac地址
            if (!ioctl(fd, SIOCGIFHWADDR, (char *)(&buf[interfaceNum])))
            {
                memset(mac, 0, sizeof(mac));
                snprintf(mac, sizeof(mac), "%02x:%02x:%02x:%02x:%02x:%02x",
                (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[0],
                (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[1],
                (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[2],
                (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[3],
                (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[4],
                (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[5]);
                printf("device mac: %s\n", mac);
            }
            else
            {
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
                close(fd);
                return -1;
            }
            //获取广播地址
            if (!ioctl(fd, SIOCGIFBRDADDR, &buf[interfaceNum]))
            {
                snprintf(broadAddr, sizeof(broadAddr), "%s",
                            (char *)inet_ntoa(((struct sockaddr_in *)&(buf[interfaceNum].ifr_broadaddr))->sin_addr));
                printf("device broadAddr: %s\n", broadAddr);
            }
            else
            {
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
                close(fd);
                return -1;
            }
        }
    }
    else
    {
        printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
        close(fd);
        return -1;
    }
    close(fd);
    return 0;
}

2.设置IP地址、子网掩码、网关地址

#include <sys/types.h>    
#include <sys/socket.h>    
#include <netinet/in.h>    
#include <net/if.h>    
#include <sys/ioctl.h>    
#include <errno.h>    
#include <string.h>    
#include <net/route.h>    
#include <unistd.h>    
#include <stdio.h> 

int SetNetworkInfo(const char *ifname, const char *ipaddr, const char *netmask, const char *gwip)
{
    struct sockaddr_in sin;
    struct ifreq ifr;
    int fd;

    bzero(&ifr, sizeof(struct ifreq));

    if (!ifname == NULL || !ipaddr || !gwip) return -1;
    fd = socket(AF_INET, SOCK_DGRAM, 0);
    if (fd == -1)
    {
        perror("Not create network socket connection\n");
        return -1;
    }

    //设置IP地址
    strncpy(ifr.ifr_name, ifname, IFNAMSIZ);
    ifr.ifr_name[IFNAMSIZ   -   1]   =   0;
    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = inet_addr(ipaddr);
    memcpy(&ifr.ifr_addr, &sin, sizeof(sin));
    if (ioctl(fd, SIOCSIFADDR, &ifr) < 0)
    {
        perror( "Not setup interface\n ");
        return -1;
    }

    //设置子网掩码
    bzero(&ifr, sizeof(struct ifreq));
    strncpy(ifr.ifr_name, ifname, IFNAMSIZ);
    ifr.ifr_name[IFNAMSIZ   -   1]   =   0;
    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = inet_addr(netmask);
    memcpy(&ifr.ifr_addr, &sin, sizeof(sin));
    if(ioctl(fd, SIOCSIFNETMASK, &ifr ) < 0)
    {
        perror("net mask ioctl error\n");
        return -1;
    }

    //设置网关地址
    struct rtentry rm;
    bzero(&rm, sizeof(struct rtentry));
    rm.rt_dst.sa_family = AF_INET;
    rm.rt_gateway.sa_family = AF_INET;
    rm.rt_genmask.sa_family = AF_INET;
    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = inet_addr(gwip);
    memcpy(&rm.rt_gateway, &sin, sizeof(sin)); 
    rm.rt_dev = (char *)ifname;
    rm.rt_flags = RTF_UP | RTF_GATEWAY ;
    if(ioctl(fd, SIOCADDRT, &rm ) < 0)
    {
        perror("gateway ioctl error\n");
        return -1;
    }

    //激活接口
    ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
    if (ioctl(fd, SIOCSIFFLAGS, &ifr) < 0)
    {
        perror("SIOCSIFFLAGS");
        return -1;
    }

    return 0;
}

二、编程获取cpu、内存和硬盘的使用率

1. 获取cpu使用率

#include <stdio.h>
#include <unistd.h>

/* cpu_info_t结构体存放cpu相关信息 */
typedef struct _cpu_info
{
    char name[20];
    unsigned int user;
    unsigned int nice;
    unsigned int system;
    unsigned int idle;
    unsigned int iowait;
    unsigned int irq;
    unsigned int softirq;
}cpu_info_t;

/* 从/proc/stat文件中获取cpu的相关信息 */
void get_cpu_occupy(cpu_info_t* info)
{
    FILE* fp = NULL;
    char buf[256] = {0};

    fp = fopen("/proc/stat", "r");
    fgets(buf, sizeof(buf), fp);

    sscanf(buf, "%s %u %u %u %u %u %u %u", info->name, &info->user, &info->nice, 
        &info->system, &info->idle, &info->iowait, &info->irq, &info->softirq);

    fclose(fp);
}

/* 计算cpu的使用率 */
double calc_cpu_rate(cpu_info_t* old_info, cpu_info_t* new_info)
{
    double od, nd;
    double usr_dif, sys_dif, nice_dif;
    double user_cpu_rate;
    double kernel_cpu_rate;

    od = (double)(old_info->user + old_info->nice + old_info->system + old_info->idle + old_info->iowait + old_info->irq + old_info->softirq);
    nd = (double)(new_info->user + new_info->nice + new_info->system + new_info->idle + new_info->iowait + new_info->irq + new_info->softirq);

    if (nd - od)
    {
        user_cpu_rate = (new_info->user - old_info->user) / (nd - od) * 100;
        kernel_cpu_rate = (new_info->system - old_info->system) / (nd - od) * 100;

        return user_cpu_rate + kernel_cpu_rate;
    }
    return 0;

}

int main(void)
{
    cpu_info_t info1;
    cpu_info_t info2;

    get_cpu_occupy(&info1);
    sleep(2);   /* 休息2s以统计cpu使用率 */
    get_cpu_occupy(&info2);

    printf("CPU的使用率: %.2lf%\n", calc_cpu_rate(&info1, &info2));

    return 0;
}

2. 获取内存使用率.

#include <stdio.h>

typedef struct _mem_info_t
{
    char name[20];
    unsigned long total;
    char name2[20];
}mem_info_t;

void get_memory_occupy()
{
    FILE* fp = NULL;
    char buf[256] = {0};
    mem_info_t info;
    double mem_total, mem_used_rate;

    fp = fopen("/proc/meminfo", "r");
    fgets(buf, sizeof(buf), fp);
    sscanf(buf, "%s %lu %s\n", info.name, &info.total, &info.name2);
    mem_total = info.total;
    fgets(buf, sizeof(buf), fp);
    sscanf(buf, "%s %lu %s\n", info.name, &info.total, &info.name2);
    mem_used_rate = (1 - info.total / mem_total) * 100;
    mem_total = mem_total / (1024 * 1024); //KB -> GB

    printf("内存大小为: %.0lfG, 占用率为: %.2lf\n", mem_total, mem_used_rate);
}

int main(void)
{
    get_memory_occupy();

    return 0;
}

3.获取磁盘使用率

#include <stdio.h>

void get_hard_drive_rate()
{
    FILE* fp = NULL;
    int h = 0;
    char buf[80], a[80], d[80], e[80], f[80];
    double b, c;
    double total = 0, used = 0;

    fp = popen("df", "r");
    fgets(buf, 256, fp);

    while (6 == fscanf(fp, "%s %lf %lf %s %s %s", a, &b, &c, d, e, f))
    {
        total += b;
        used += c;
    }
    pclose(fp);
    printf("磁盘总大小: %.4lfG, 使用率: %.2lf%\n", total / (1024 * 1024), used / total * 100);
}

int main(void)
{
    get_hard_drive_rate();

    return 0;
}