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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

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       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at https://www.kernel.org/doc/man-pages/.