linux - How to display groupID (GID) correctly in C? -

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i'm trying display userid , groupid through 1 of functions in c program. userid displaying correctly (501) groupid isn't. when check groupid using command "id -g" 20 when run through program using function value 1.

this code.

int registerpw(char **args){      register struct passwd *pw;     register uid_t uid;     int c;     register gid_t gid;     register struct group *grp;     grp = getgrgid(gid);      uid = geteuid();     pw = getpwuid(uid);       if (pw)     {             printf("%d,",uid);      // userid             printf("%d,", gid);    //groupid             puts (pw->pw_name);             puts(grp->gr_name);       }     else{         printf("failed\n");     }     return 1; }

my output 

501,1,username daemon

your code merely declared & defined variable of gid, left value uninitialized. shall assign correct value it:

register gid_t gid; gid = getgid();

or simply:

register gid_t gid = getgid();

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