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 *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


   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 appropriately.  If one wants
   to check errno after the call, it should be  set  to  zero  before  the

   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.


   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.


          local password database file

          System Databases and Name Service Switch configuration file


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

   │InterfaceAttributeValue                       │
   │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 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.


   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);


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


   This  page  is  part of release 4.09 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


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