getpwnam_r(3) — Linux manual page


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

NAME         top

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

SYNOPSIS         top

       #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():
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION         top

       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 informa‐
       tion 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

       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.)

RETURN VALUE         top

       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         top

       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 reached.

       ENOMEM Insufficient memory to allocate passwd structure.

       ERANGE Insufficient buffer space supplied.

FILES         top

              local password database file

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │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()  │               │                             │

CONFORMING TO         top

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

NOTES         top

       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.

EXAMPLES         top

       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 <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: %ld\n", pwd.pw_gecos, (long) pwd.pw_uid);

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 5.08 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                              2020-06-09                      GETPWNAM(3)

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