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\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), 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)