PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

NAME

       getgrnam, getgrnam_r — search group database for a name

SYNOPSIS

       #include <grp.h>

       struct group *getgrnam(const char *name);
       int getgrnam_r(const char *name, struct group *grp, char *buffer,
           size_t bufsize, struct group **result);

DESCRIPTION

       The getgrnam() function shall search the group database for an entry with a matching name.

       The getgrnam() function need not be thread-safe.

       The  getgrnam_r() function shall update the group structure pointed to by grp and store a pointer to that
       structure at the location pointed to by result.  The structure shall contain  an  entry  from  the  group
       database  with  a  matching name.  Storage referenced by the group structure is allocated from the memory
       provided   with   the   buffer   parameter,   which   is   bufsize   bytes   in   size.   A    call    to
       sysconf(_SC_GETGR_R_SIZE_MAX)  returns either −1 without changing errno or an initial value suggested for
       the size of this buffer.  A null pointer is returned at the location pointed to by result on error or  if
       the requested entry is not found.

RETURN VALUE

       The  getgrnam()  function  shall return a pointer to a struct group with the structure defined in <grp.h>
       with a matching entry if one is found. The getgrnam() function shall return a null pointer if either  the
       requested entry was not found, or an error occurred. On error, errno shall be set to indicate the error.

       The  application  shall  not modify the structure to which the return value points, nor any storage areas
       pointed to by pointers within the structure. The returned pointer, and  pointers  within  the  structure,
       might  be  invalidated or the structure or the storage areas might be overwritten by a subsequent call to
       getgrent(), getgrgid(), or getgrnam().

       The getgrnam_r() function shall return zero on success or if the requested entry was  not  found  and  no
       error has occurred. If any error has occurred, an error number shall be returned to indicate the error.

ERRORS

       The getgrnam() and getgrnam_r() functions may fail if:

       EIO    An I/O error has occurred.

       EINTR  A signal was caught during getgrnam().

       EMFILE All file descriptors available to the process are currently open.

       ENFILE The maximum allowable number of files is currently open in the system.

       The getgrnam_r() function may fail if:

       ERANGE Insufficient  storage  was supplied via buffer and bufsize to contain the data to be referenced by
              the resulting group structure.

       The following sections are informative.

EXAMPLES

       Note that sysconf(_SC_GETGR_R_SIZE_MAX) may return −1 if there is no hard limit on the size of the buffer
       needed  to  store all the groups returned. This example shows how an application can allocate a buffer of
       sufficient size to work with getgrnam_r().

           long int initlen = sysconf(_SC_GETGR_R_SIZE_MAX);
           size_t len;
           if (initlen == −1)
               /* Default initial length. */
               len = 1024;
           else
               len = (size_t) initlen;
           struct group result;
           struct group *resultp;
           char *buffer = malloc(len);
           if (buffer == NULL)
               ...handle error...
           int e;
           while ((e = getgrnam_r("somegroup", &result, buffer, len, &resultp))
                   == ERANGE)
               {
               size_t newlen = 2 * len;
               if (newlen < len)
                   ...handle error...
               len = newlen;
               char *newbuffer = realloc(buffer, len);
               if (newbuffer == NULL)
                   ...handle error...
               buffer = newbuffer;
               }
           if (e != 0)
               ...handle error...
           free (buffer);

APPLICATION USAGE

       Applications wishing to check for error situations should set errno to 0 before calling  getgrnam().   If
       errno is set on return, an error occurred.

       The  getgrnam_r()  function  is  thread-safe and shall return values in a user-supplied buffer instead of
       possibly using a static data area that may be overwritten by each call.

       Portable applications should take into account that it is usual for an implementation to return  −1  from
       sysconf() indicating that there is no maximum for _SC_GETGR_R_SIZE_MAX.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       endgrent(), getgrgid(), sysconf()

       The Base Definitions volume of POSIX.1‐2008, <grp.h>, <sys_types.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications  Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc
       and The Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In  the  event
       of  any  discrepancy between this version and the original IEEE and The Open Group Standard, the original
       IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at
       http://www.unix.org/online.html .

       Any  typographical  or formatting errors that appear in this page are most likely to have been introduced
       during  the  conversion  of  the  source  files  to  man  page  format.  To  report  such   errors,   see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .