getpwnam(3)                                           Library Functions Manual                                          getpwnam(3)

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

       Standard C library (libc, -lc)

       #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 buf[restrict .buflen], size_t buflen,
                      struct passwd **restrict result);
       int getpwuid_r(uid_t uid, struct passwd *restrict pwd,
                      char buf[restrict .buflen], 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 re‐
       trieved passwd structure in the space pointed to by pwd.  The string fields pointed to by the members of the  passwd  struc‐
       ture  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 getp‐
       wuid().  (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

       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.

       The user password database mostly refers to /etc/passwd.  However, with recent systems it also refers to network wide  data‐
       bases using NIS, LDAP and other local files as configured in /etc/nsswitch.conf.

              local password database file

              System Databases and Name Service Switch configuration 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(), getpwuid_r() │ Thread safety │ MT-Safe locale                                                                │

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

       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 di‐
       rectory 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 argument.

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

       main(int argc, char *argv[])
           struct passwd pwd;
           struct passwd *result;
           char *buf;
           long 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), nsswitch.conf(5),

Linux man-pages 6.03                                         2023-02-05                                                 getpwnam(3)