C + + access to Linux and Windows system user name

(1) Obtain the user name of Linux system:
Through struct passwd *getpwuid (uid_t uid) function; This function returns the passwd structure, which contains the User name field
struct passwd {char *pw_name;  /*user name */char *pw_passwd;  /*user Password * * uid_t pw_uid;  /*user ID */gid_t pw_gid;  /*group ID */char *pw_gecos;  /*user real name */char *pw_dir;  /*home Directory * * Char *pw_shell; /*shell program */};
(2) Obtain the user name of the Windows system:
Through the GetUserName (buffer, &len) function

(3) Complete instance (cross platform):
[CPP]  View plain  copy #include  <iostream>   #include  <string>      #ifdef  linux        #include  <unistd.h>        #include  <pwd.h>   #endif       #ifdef  _ win32        #include <Windows.h>   #endif       Std::string getusername ()    {   #if  defined linux   //linux  system       uid_t userid;       struct  passwd* pwd;       userid=getuid ();        pwd=getpwuid (userid);       return pwd->pw_name;       #elif  defined _WIN32  //windows system       const  int max_len = 100;       char szBuffer[MAX_LEN];       DWORD len = MAX_LEN;       if (  GetUserName (Szbuffer, &len)  )      //username is saved in Szbuffer, Len is the length of user name             return szBuffer;      #else    //outher system       return  "";   #endif   }       int main ()    {       std::string ss  = getusername ();       std::cout << ss <<  std::endl;       return 0;  }   (4) GCC compile run screenshot on Linux system
(5) Linux under the four simple function introduction: Getpid, Getppid, Getuid, Getgid

#include <stdio.h>  
  
int main ()  
{  
    printf ("pid:%d, ppid:%d, uid:%d, gid:%d\n", Getpid (), Getppid (), Getuid (), Getgid ());  
    return 0;  
}  

The result is: [Taoge@localhost learn_c]$ Echo $$
2774
[Taoge@localhost learn_c]$ ID
uid=501 (Taoge) gid=502 (taoge) groups=502 (Taoge), 501 (embed)
[Taoge@localhost learn_c]$./a.out
pid:2898, ppid:2774, uid:501, gid:502
[Taoge@localhost learn_c]$ su Root
Password:
[Root@localhost learn_c]# Echo &&
>
[Root@localhost learn_c]# ID
Uid=0 (Root) gid=0 (root) groups=0 (root), 1 (BIN), 2 (daemon), 3 (SYS), 4 (ADM), 6 (disk), (wheel)
[Root@localhost learn_c]#./a.out
pid:2922, ppid:2905, uid:0, gid:0
[Root@localhost learn_c]# su Taoge
[Taoge@localhost learn_c]$ Echo $$
2928
[Taoge@localhost learn_c]$ ID
uid=501 (Taoge) gid=502 (taoge) groups=502 (Taoge), 501 (embed)
[Taoge@localhost learn_c]$./a.out
pid:2946, ppid:2928, uid:501, gid:502
[Taoge@localhost learn_c]$

 #include <unistd.h> #include <pwd.h> void Getuserandpid () {uid_t userid;
  struct passwd* pwd;
  Userid=getuid ();
  Pwd=getpwuid (userid);
  FILE *FP = fopen ("/home/stamp_temp/ao.log", "ab+");
  fprintf (FP, "user:%s, pid:%d, ppid:%d, uid:%d, gid:%d\n", Pwd->pw_name, Getpid (), Getppid (), Getuid (), Getgid ());
Fclose (FP); }