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GETGRNAM(3P)               POSIX Programmer's Manual              GETGRNAM(3P)
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 data-
       base 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  loca-
       tion  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  getgr-
       nam().
       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 con-
              tain 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 Electri-
       cal  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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                         GETGRNAM(3P)