banan-os/userspace/programs/id/main.cpp

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#include <stdio.h>
#include <unistd.h>
#include <pwd.h>
int main()
{
uid_t uid = getuid();
uid_t euid = geteuid();
gid_t gid = getgid();
gid_t egid = getegid();
passwd* pw_uid = getpwuid(uid);
if (pw_uid == nullptr)
{
fprintf(stderr, "Unknown user #%d\n", uid);
return 1;
}
passwd* pw_euid = getpwuid(euid);
if (pw_euid == nullptr)
{
fprintf(stderr, "Unknown user #%d\n", euid);
return 1;
}
printf("uid=%u(%s)", uid, pw_uid->pw_name);
if (uid != euid)
printf(",euid=%u(%s)",euid, pw_euid->pw_name);
printf(" gid=%u", gid);
if (gid != egid)
printf(",egid=%u", egid);
printf("\n");
}