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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	 user‐
       name 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 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;      /* user information */
	       char   *pw_dir;	      /* home directory */
	       char   *pw_shell;      /* shell program */
	   };

       See passwd(5) for more information about these fields.

       The getpwnam_r() and getpwuid_r() functions obtain the same information
       as getpwnam() and getpwuid(), but store the retrieved passwd  structure
       in  the	space  pointed to by pwd.  The string fields pointed to by the
       members of the passwd structure 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 call

	   sysconf(_SC_GETPW_R_SIZE_MAX)

       returns either -1, without changing errno, or an initial suggested size
       for  buf.   (If	this size is too small, the call fails with ERANGE, in
       which case the caller can retry with a larger buffer.)

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.

NOTE
       The user password database mostly refers to /etc/passwd.	 However, with
       recent systems it also refers to network wide databases using NIS, LDAP
       and other local files as configured in /etc/nsswitch.conf.

FILES
       /etc/passwd
	      local password database file

       /etc/nsswitch.conf
	      System Databases and Name Service Switch configuration file

ATTRIBUTES
   Multithreading (see pthreads(7))
       The getpwnam() and getpwuid() functions are not thread-safe.

       The getpwnam_r() and getpwuid_r() functions are thread-safe.

CONFORMING TO
       SVr4, 4.3BSD, POSIX.1-2001.  The pw_gecos field	is  not	 specified  in
       POSIX, but is present on most implementations.

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 var‐
       ious 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	 argu‐
       ment.

       #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\n", 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\n");
	       else {
		   errno = s;
		   perror("getpwnam_r");
	       }
	       exit(EXIT_FAILURE);
	   }

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

SEE ALSO
       endpwent(3),  fgetpwent(3),  getgrnam(3), getpw(3), getpwent(3), getsp‐
       nam(3), putpwent(3), setpwent(3), nsswitch.conf(5), passwd(5)

COLOPHON
       This page is part of release 3.54 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				  2013-07-22			   GETPWNAM(3)
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