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 .