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man:getgrnam_r

GETGRNAM(3) Linux Programmer's Manual GETGRNAM(3)

NAME

     getgrnam, getgrnam_r, getgrgid, getgrgid_r - get group file entry

SYNOPSIS

     #include <sys/types.h>
     #include <grp.h>
     struct group *getgrnam(const char *name);
     struct group *getgrgid(gid_t gid);
     int getgrnam_r(const char *name, struct group *grp,
               char *buf, size_t buflen, struct group **result);
     int getgrgid_r(gid_t gid, struct group *grp,
               char *buf, size_t buflen, struct group **result);
 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
     getgrnam_r(), getgrgid_r():
         _POSIX_C_SOURCE
             || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

     The getgrnam() function returns a pointer to a structure containing the
     broken-out fields of the record in the group database (e.g., the  local
     group file /etc/group, NIS, and LDAP) that matches the group name name.
     The getgrgid() function returns a pointer to a structure containing the
     broken-out  fields of the record in the group database that matches the
     group ID gid.
     The group structure is defined in <grp.h> as follows:
         struct group {
             char   *gr_name;        /* group name */
             char   *gr_passwd;      /* group password */
             gid_t   gr_gid;         /* group ID */
             char  **gr_mem;         /* NULL-terminated array of pointers
                                        to names of group members */ };
     For more information about the fields of this structure, see  group(5).
     The getgrnam_r() and getgrgid_r() functions obtain the same information
     as getgrnam() and getgrgid(), but store the retrieved  group  structure
     in  the  space  pointed to by grp.  The string fields pointed to by the
     members of the group 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_GETGR_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 getgrnam() and getgrgid() functions return a  pointer  to  a  group
     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  getgrent(3), getgrgid(), or getgrnam().  (Do not
     pass the returned pointer to free(3).)
     On success, getgrnam_r() and getgrgid_r() return zero, and set  *result
     to  grp.  If no matching group 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 gid 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 group structure.
     ERANGE Insufficient buffer space supplied.

FILES

     /etc/group
            local group database file

ATTRIBUTES

     For   an   explanation   of   the  terms  used  in  this  section,  see
     attributes(7).
     allbox; lb lb  lb  l  l  l.   Interface Attribute Value  T{  getgrnam()
     T}   Thread    safety MT-Unsafe   race:grnam   locale   T{   getgrgid()
     T}   Thread safety  MT-Unsafe race:grgid locale T{ getgrnam_r(),
     getgrgid_r() T}   Thread safety  MT-Safe locale

CONFORMING TO

     POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.

NOTES

     The formulation given above under "RETURN VALUE" is from  POSIX.1.   It
     does  not  call "not found" an error, 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 sit-
     uation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM, and probably  oth-
     ers.

SEE ALSO

     endgrent(3),   fgetgrent(3),   getgrent(3),  getpwnam(3),  setgrent(3),
     group(5)

COLOPHON

     This page is part of release 4.16 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/.
                                2017-09-15                       GETGRNAM(3)
/data/webs/external/dokuwiki/data/pages/man/getgrnam_r.txt · Last modified: 2019/05/17 09:32 by 127.0.0.1

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