[C++知识库]一些 shell 命令的C语言简要实现

uname 打印系统信息

系统命令

$ uname 
Linux

c 语言实现

#include <stdio.h>
#include <sys/utsname.h>

int main(int argc, char **argv)
{
    struct utsname name;
    if (uname(&name) < 0) {
        perror("uname error");
        return -1;
    }
    printf("%s\n%s\n%s\n%s\n%s\n",
            name.sysname, name.nodename, name.release, 
            name.version, name.machine);
    return 0;
}

whoami 打印用户名

系统命令

$ whoami
yourname

c 语言实现

#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <pwd.h>
#include <stdio.h>

int main(int argc, char **argv)
{
    struct passwd *pw;
    uid_t uid;
    uid_t NO_UID = -1;

    /* return the effective user ID of the calling process */
    uid = geteuid();    
    if (uid == NO_UID && errno) {
        perror("geteuid error");
        return -1;
    }

    /* return the pointer of the password database that matches the uid */
    pw = getpwuid(uid); 
    if (!pw) {
        perror("getpwuid error");
        return -1;
    }
    puts(pw->pw_name);

    return 0;
}