unix에서 password변경하는 함수 만들기.

#include < stdio.h>
#include < stdlib.h>
#include < unistd.h>
#include < pwd.h>
#include < shadow.h>
 
int main(int argc, char *argv[])
{
        struct spwd *shadow;
        struct passwd *ppasswd;
        char *password;
        int auth;
 
        if ( argc < 3 ) {
                printf("\nUsage: passauth USER PASS\n\n");
                exit(1);
        }
 
        if ( NULL == (ppasswd=getpwnam(argv[1])) ) {
                printf("\nUser not exist.\n\n");
                exit(1);
        }
 
//      password=getpass("   Enter Password: ");
        password=argv[2];
 
        if ( ! strcmp( ppasswd->pw_passwd, "x" ) ) {
                shadow=getspnam(argv[1]);
                if ( strcmp( shadow->sp_pwdp, (char *)crypt(password, shadow->sp_pwdp)) )
                        auth=1;
                else
                        auth=0;
        }
        else {
                if ( strcmp( ppasswd->pw_passwd, (char *)crypt(password, ppasswd->pw_passwd)) )
                        auth=1;
                else
                        auth=0;
        }
 
/*
        if ( auth == 0 ) {
                printf("home directory   : %s\n", ppasswd->pw_dir);
                printf("shell program    : %s\n", ppasswd->pw_shell);
                if ( strcmp( ppasswd->pw_passwd, "x" ) )
                        printf("encrypted passwd : %s\n", ppasswd->pw_passwd);
                else
                        printf("encrypted passwd : %s\n", shadow->sp_pwdp);
        }
*/
 
        return auth;
}