source: vendor/bash/3.1-p17/examples/loadables/id.c

/*
 * id - POSIX.2 user identity
 *
 * (INCOMPLETE -- supplementary groups for other users not yet done)
 *
 * usage: id [-Ggu] [-nr] [user]
 *
 * The default output format looks something like:
 *      uid=xxx(chet) gid=xx groups=aa(aname), bb(bname), cc(cname)
 */

#include <config.h>
#include <stdio.h>
#include "bashtypes.h"
#include <pwd.h>
#include <grp.h>
#include "bashansi.h"

#ifdef HAVE_LIMITS_H
#  include <limits.h>
#else
#  include <sys/param.h>
#endif

#if !defined (HAVE_GETPW_DECLS)
extern struct passwd *getpwuid ();
#endif
extern struct group *getgrgid ();

#include "shell.h"
#include "builtins.h"
#include "stdc.h"
#include "common.h"
#include "bashgetopt.h"

#define ID_ALLGROUPS    0x001           /* -G */
#define ID_GIDONLY      0x002           /* -g */
#define ID_USENAME      0x004           /* -n */
#define ID_USEREAL      0x008           /* -r */
#define ID_USERONLY     0x010           /* -u */

#define ID_FLAGSET(s)   ((id_flags & (s)) != 0)

static int id_flags;

static uid_t ruid, euid;
static gid_t rgid, egid;

static char *id_user;

static int inituser ();

static int id_pruser ();
static int id_prgrp ();
static int id_prgroups ();
static int id_prall ();

int
id_builtin (list)
     WORD_LIST *list;
{
  int opt;
  char *user;

  id_flags = 0;
  reset_internal_getopt ();
  while ((opt = internal_getopt (list, "Ggnru")) != -1)
    {
      switch (opt)
        {
        case 'G': id_flags |= ID_ALLGROUPS; break;
        case 'g': id_flags |= ID_GIDONLY; break;
        case 'n': id_flags |= ID_USENAME; break;
        case 'r': id_flags |= ID_USEREAL; break;
        case 'u': id_flags |= ID_USERONLY; break;
        default:
          builtin_usage ();
          return (EX_USAGE);
        }
    }
  list = loptend;

  user = list ? list->word->word : (char *)NULL;

  /* Check for some invalid option combinations */
  opt = ID_FLAGSET (ID_ALLGROUPS) + ID_FLAGSET (ID_GIDONLY) + ID_FLAGSET (ID_USERONLY);
  if (opt > 1 || (opt == 0 && ((id_flags & (ID_USEREAL|ID_USENAME)) != 0)))
    {
      builtin_usage ();
      return (EX_USAGE);
    }

  if (list && list->next)
    {
      builtin_usage ();
      return (EX_USAGE);
    }

  if (inituser (user) < 0)
    return (EXECUTION_FAILURE);

  opt = 0;
  if (id_flags & ID_USERONLY)
    opt += id_pruser ((id_flags & ID_USEREAL) ? ruid : euid);
  else if (id_flags & ID_GIDONLY)
    opt += id_prgrp ((id_flags & ID_USEREAL) ? rgid : egid);
  else if (id_flags & ID_ALLGROUPS)
    opt += id_prgroups (user);
  else
    opt += id_prall (user);
  putchar ('\n');
  fflush (stdout);

  return (opt == 0 ? EXECUTION_SUCCESS : EXECUTION_FAILURE);
}

static int
inituser (uname)
     char *uname;
{
  struct passwd *pwd;

  if (uname)
    {
      pwd = getpwnam (uname);
      if (pwd == 0)
        {
          builtin_error ("%s: no such user", uname);
          return -1;
        }
      ruid = euid = pwd->pw_uid;
      rgid = egid = pwd->pw_gid;
    }
  else
    {
      ruid = current_user.uid;
      euid = current_user.euid;
      rgid = current_user.gid;
      egid = current_user.egid;
    }
  return 0;
}

/* Print the name or value of user ID UID. */
static int
id_pruser (uid)
     int uid;
{
  struct passwd *pwd = NULL;
  int r;

  r = 0;
  if (id_flags & ID_USENAME)
    {
      pwd = getpwuid (uid);
      if (pwd == NULL)
        r = 1;
    }
  if (pwd)
    printf ("%s", pwd->pw_name);
  else
    printf ("%u", (unsigned) uid);
      
  return r;
}

/* Print the name or value of group ID GID. */

static int
id_prgrp (gid)
     int gid;
{
  struct group *grp = NULL;
  int r;

  r = 0;
  if (id_flags & ID_USENAME)
    {
      grp = getgrgid (gid);
      if (grp == NULL)
        r = 1;
    }

  if (grp)
    printf ("%s", grp->gr_name);
  else
    printf ("%u", (unsigned) gid);

  return r;
}

static int
id_prgroups (uname)
     char *uname;
{
  int *glist, ng, i, r;

  r = 0;
  id_prgrp (rgid);
  if (egid != rgid)
    {
      putchar (' ');
      id_prgrp (egid);
    }

  if (uname)
    {
      builtin_error ("supplementary groups for other users not yet implemented");
      glist = (int *)NULL;
      ng = 0;
      r = 1;
    }
  else
    glist = get_group_array (&ng);

  for (i = 0; i < ng; i++)
    if (glist[i] != rgid && glist[i] != egid)
      {
        putchar (' ');
        id_prgrp (glist[i]);
      }
  
  return r;
}

static int
id_prall (uname)
     char *uname;
{
  int r, i, ng, *glist;
  struct passwd *pwd;
  struct group *grp;

  r = 0;
  printf ("uid=%u", (unsigned) ruid);
  pwd = getpwuid (ruid);
  if (pwd == NULL)
    r = 1;
  else
    printf ("(%s)", pwd->pw_name);

  printf (" gid=%u", (unsigned) rgid);
  grp = getgrgid (rgid);
  if (grp == NULL)
    r = 1;
  else
    printf ("(%s)", grp->gr_name);

  if (euid != ruid)
    { 
      printf (" euid=%u", (unsigned) euid);
      pwd = getpwuid (euid);
      if (pwd == NULL)
        r = 1;
      else 
        printf ("(%s)", pwd->pw_name);
    }

  if (egid != rgid) 
    {
      printf (" egid=%u", (unsigned) egid);
      grp = getgrgid (egid);
      if (grp == NULL)
        r = 1;
      else
        printf ("(%s)", grp->gr_name);
    }

  if (uname)
    {
      builtin_error ("supplementary groups for other users not yet implemented");
      glist = (int *)NULL;
      ng = 0;
      r = 1;
    }
  else
    glist = get_group_array (&ng);

  if (ng > 0)
    printf (" groups=");
  for (i = 0; i < ng; i++)
    {
      if (i > 0)
        printf (", ");
      printf ("%u", (unsigned) glist[i]);
      grp = getgrgid (glist[i]);
      if (grp == NULL)
        r = 1;
      else
        printf ("(%s)", grp->gr_name);
    }

  return r;
}

char *id_doc[] = {
        "return information about user identity",
        (char *)NULL
};

struct builtin id_struct = {
        "id",
        id_builtin,
        BUILTIN_ENABLED,
        id_doc,
        "id [user]\n\tid -G [-n] [user]\n\tid -g [-nr] [user]\n\tid -u [-nr] [user]",
        0
};