getpwnam_r

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  getpwnam_r()  and  getpwuid_r() functions obtain the same informa-
       tion, 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
       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

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 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
       {
           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), getsp-
       nam(3), putpwent(3), setpwent(3), nsswitch.conf(5), passwd(5)

COLOPHON
       This page is part of release 3.23 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)