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

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

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

       struct passwd *getpwnam(const char *name);
       struct passwd *getpwuid(uid_t uid);

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

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

       getpwnam_r(), getpwuid_r():
               || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

       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 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


       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.)

       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 to indicate the error.  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.

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

       EINTR  A signal was caught; see signal(7).

       EIO    I/O error.

       EMFILE The per-process limit on the number of open file descriptors has
              been reached.

       ENFILE The system-wide limit on the total number of open files has been

       ENOMEM Insufficient memory to allocate passwd structure.

       ERANGE Insufficient buffer space supplied.

              local password database file

       For an explanation of the terms used in this section, see attributes(7).

       │Interface     Attribute     Value                                   │
       │getpwnam()    │ Thread safety │ MT-Unsafe race:pwnam locale             │
       │getpwuid()    │ Thread safety │ MT-Unsafe race:pwuid locale             │
       │getpwnam_r(), │ Thread safety │ MT-Safe locale                          │
       │getpwuid_r()  │               │                                         │

       POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.  The pw_gecos field is not
       specified in POSIX, but is present on most implementations.

       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

       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.

       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

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

       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]);

           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) {

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

           printf("Name: %s; UID: %jd\n", pwd.pw_gecos,
                   (intmax_t) pwd.pw_uid);

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

       This page is part of release 5.13 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

GNU                                2021-03-22                        GETPWNAM(3)