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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 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  struc-
       ture 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), getpw-
       nam(), 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 rec-
       ognize 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  getp-
       wuid(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  getpw-
       nam("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\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: %ld0, 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 3.22 of the Linux man-pages project.  A description of the project, and informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



GNU                               2009-03-30                       GETPWNAM(3)