focal (3) getpwuid.3.gz

Provided by: manpages-dev_5.05-1_all bug

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
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_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 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

           sysconf(_SC_GETPW_R_SIZE_MAX)

       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

       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; 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.

NOTE

       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.

FILES

       /etc/passwd
              local password database file

       /etc/nsswitch.conf
              System Databases and Name Service Switch configuration file

ATTRIBUTES

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

       ┌──────────────┬───────────────┬─────────────────────────────┐
       │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()  │               │                             │
       └──────────────┴───────────────┴─────────────────────────────┘

CONFORMING TO

       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

       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.

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: %ld\n", pwd.pw_gecos, (long) pwd.pw_uid);
           exit(EXIT_SUCCESS);
       }

SEE ALSO

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

COLOPHON

       This page is part of release 5.05 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
       https://www.kernel.org/doc/man-pages/.