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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  struc-
       ture  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  pro-
              cess.

       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 vari-
       able  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   getp-
       wuid(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: %ld0, pwd.pw_gecos, (long) pwd.pw_uid);
           exit(EXIT_SUCCESS);
       }

SEE ALSO
       endpwent(3), fgetpwent(3), getgrnam(3), getpw(3), getpwent(3),  getspnam(3),  putp-
       went(3), setpwent(3), passwd(5)

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of
       the project, and information about reporting bugs, can be found at  http://www.ker-
       nel.org/doc/man-pages/.



GNU                               2009-03-30                       GETPWNAM(3)

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