[linux] 사용자 정보 구하기

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LAB> 사용자의 정보를 구하는 프로그래밍을 해보자.

# vi struct.c
-- struct.c --
#include <stdio.h>

struct test
{
  int i;
  int j;
};

int main()
{
  struct test abc;
  abc.i = 10;
  abc.j = 20;

  printf("abc.i = %d, abc.j = %d \n", abc.i, abc.j);

  return 0;
}
-- struct.c --

# gcc -o struct struct.c 
# ./struct 
abc.i = 10, abc.j = 20 

# cp struct.c struct2.c
# vi struct2.c
-- struct2.c --
#include <stdio.h>

struct test
{
  int i;
  int j;
};

int main()
{
  struct test abc, *p;
  p = &abc;
  p->i = 10;
  p->j = 20;

  printf("p->i = %d, p->j = %d \n", p->i, p->j);

  return 0;
}


# vi userinfo.c
-- userinfo.c --
#include <stdio.h>       // /usr/include/stdio.h
#include <unistd.h>      // /usr/include/unistd.h
#include <pwd.h>         // /usr/include/pwd.h
#include <sys/types.h>   // /usr/include/sys/types.h

int main()
{
  char username[] = "bluesky";
  struct passwd *userpw;
  
  userpw = getpwnam(username);

  printf("account : %s \n"
         "uid : %d \n"
         "gid : %d \n"
         "comment : %d \n"
         "home dir : %s \n"
         "shell : %s \n", userpw->pw_name, userpw->pw_uid
                        , userpw->pw_gid,  userpw->pw_gecos
                        , userpw->pw_dir,  userpw->pw_shell
         );
  
  return 0;
}
-- userinfo.c --

# gcc -o userinfo userinfo.c 
# ./userinfo 
account : bluesky 
uid : 7000 
gid : 9000 
comment : 148201500 
home dir : /home1/bluesky 
shell : /bin/sh

# usermod -g 100 bluesky
# grep bluesky /etc/passwd
bluesky:x:7000:100:testuser1:/home1/bluesky:/bin/sh
# ./userinfo 
account : bluesky 
uid : 7000 
gid : 100 
comment : 157347867 
home dir : /home1/bluesky 
shell : /bin/sh 

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