GETPWNAM(3)						     Linux Programmer's Manual						       GETPWNAM(3)

NAME

       getpwnam, getpwnam_r, getpwuid, getpwuid_r - get password file entry

SYNOPSIS

       #include <sys/types.h>
       #include <pwd.h>

       struct passwd *getpwnam(const char *name);

       struct passwd *getpwuid(uid_t uid);

       int getpwnam_r(const char *name, struct passwd *pwd,
		   char *buf, size_t buflen, struct passwd **result);

       int getpwuid_r(uid_t uid, struct passwd *pwd,
		   char *buf, size_t buflen, struct passwd **result);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       getpwnam_r(), getpwuid_r(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _BSD_SOURCE || _SVID_SOURCE || _POSIX_SOURCE

DESCRIPTION

       The getpwnam() function returns a pointer to a structure containing the broken-out fields of the record in the password database (e.g., the
       local password file /etc/passwd, NIS, and LDAP) that matches the username name.

       The getpwuid() function returns a pointer to a structure containing the broken-out fields of the  record  in  the  password  database  that
       matches the user ID uid.

       The  getpwnam_r()  and getpwuid_r() functions obtain the same information, but store the retrieved passwd structure in the space pointed to
       by pwd.	This passwd structure contains pointers to strings, and these strings are stored in the buffer buf of size buflen.  A  pointer	to
       the result (in case of success) or NULL (in case no entry was found or an error occurred) is stored in *result.

       The passwd structure is defined in <pwd.h> as follows:

	   struct passwd {
	       char   *pw_name;       /* username */
	       char   *pw_passwd;     /* user password */
	       uid_t   pw_uid;	      /* user ID */
	       gid_t   pw_gid;	      /* group ID */
	       char   *pw_gecos;      /* real name */
	       char   *pw_dir;	      /* home directory */
	       char   *pw_shell;      /* shell program */
	   };

       The maximum needed size for buf can be found using sysconf(3) with the argument _SC_GETPW_R_SIZE_MAX.

RETURN VALUE

       The  getpwnam()	and  getpwuid()  functions  return a pointer to a passwd structure, or NULL if the matching entry is not found or an error
       occurs.	If an error occurs, errno is set appropriately.  If one wants to check errno after the call, it should be set to zero  before  the
       call.

       The return value may point to a static area, and may be overwritten by subsequent calls to getpwent(3), getpwnam(), or getpwuid().  (Do not
       pass the returned pointer to free(3).)

       On success, getpwnam_r() and getpwuid_r() return zero, and set *result to pwd.  If no matching password record was found,  these  functions
       return 0 and store NULL in *result.  In case of error, an error number is returned, and NULL is stored in *result.

ERRORS

       0 or ENOENT or ESRCH or EBADF or EPERM or ...
	      The given name or uid was not found.

       EINTR  A signal was caught.

       EIO    I/O error.

       EMFILE The maximum number (OPEN_MAX) of files was open already in the calling process.

       ENFILE The maximum number of files was open already in the system.

       ENOMEM Insufficient memory to allocate passwd structure.

       ERANGE Insufficient buffer space supplied.

FILES

       /etc/passwd
	      local password database file

CONFORMING TO

       SVr4, 4.3BSD, POSIX.1-2001.

NOTES

       The  formulation  given above under "RETURN VALUE" is from POSIX.1-2001.  It does not call "not found" an error, and hence does not specify
       what value errno might have in this situation.  But that makes it impossible to recognize errors.  One might argue that according to  POSIX
       errno should be left unchanged if an entry is not found.  Experiments on various Unix-like systems show that lots of different values occur
       in this situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM and probably others.

       The pw_dir field contains the name of the initial working directory of the user.  Login programs use the value of this field to	initialize
       the  HOME  environment  variable  for the login shell.  An application that wants to determine its user's home directory should inspect the
       value of HOME (rather than the value getpwuid(getuid())->pw_dir) since this allows the user to modify their notion of "the home	directory"
       during  a login session.  To determine the (initial) home directory of another user, it is necessary to use getpwnam("username")->pw_dir or
       similar.

EXAMPLE

       The program below demonstrates the use of getpwnam_r() to find the full username and user ID for the username supplied  as  a  command-line
       argument.

       #include <pwd.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <unistd.h>
       #include <errno.h>

       int
       main(int argc, char *argv[])
       {
	   struct passwd pwd;
	   struct passwd *result;
	   char *buf;
	   size_t bufsize;
	   int s;

	   if (argc != 2) {
	       fprintf(stderr, "Usage: %s username
", argv[0]);
	       exit(EXIT_FAILURE);
	   }

	   bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
	   if (bufsize == -1)	       /* Value was indeterminate */
	       bufsize = 16384;        /* Should be more than enough */

	   buf = malloc(bufsize);
	   if (buf == NULL) {
	       perror("malloc");
	       exit(EXIT_FAILURE);
	   }

	   s = getpwnam_r(argv[1], &pwd, buf, bufsize, &result);
	   if (result == NULL) {
	       if (s == 0)
		   printf("Not found
");
	       else {
		   errno = s;
		   perror("getpwnam_r");
	       }
	       exit(EXIT_FAILURE);
	   }

	   printf("Name: %s; UID: %ld
", pwd.pw_gecos, (long) pwd.pw_uid);
	   exit(EXIT_SUCCESS);
       }

SEE ALSO

       endpwent(3), fgetpwent(3), getgrnam(3), getpw(3), getpwent(3), getspnam(3), putpwent(3), setpwent(3), passwd(5)

COLOPHON

       This  page is part of release 3.25 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

GNU
								    2009-03-30							       GETPWNAM(3)