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NAME

       explain_getgroups - explain getgroups(2) errors

SYNOPSIS

       #include <libexplain/getgroups.h>
       const char *explain_getgroups(int data_size, gid_t *data);
       const char *explain_errno_getgroups(int errnum, int data_size, gid_t
       *data);
       void explain_message_getgroups(char *message, int message_size, int
       data_size, gid_t *data);
       void explain_message_errno_getgroups(char *message, int message_size,
       int errnum, int data_size, gid_t *data);

DESCRIPTION

       These functions may be used to obtain explanations for errors  returned
       by the getgroups(2) system call.

   explain_getgroups
       const char *explain_getgroups(int data_size, gid_t *data);

       The  explain_getgroups  function is used to obtain an explanation of an
       error returned by the getgroups(2) system call. The least  the  message
       will  contain  is  the value of strerror(errno), but usually it will do
       much better, and indicate the underlying cause in more detail.

       The errno global variable will be used to obtain the error value to  be
       decoded.

       data_size
               The  original  data_size, exactly as passed to the getgroups(2)
               system call.

       data    The original data, exactly as passed to the getgroups(2) system
               call.

       Returns:
               The message explaining the error. This message buffer is shared
               by all libexplain functions which do not  supply  a  buffer  in
               their argument list.  This will be overwritten by the next call
               to any libexplain function which shares this buffer,  including
               other threads.

       Note:  This  function  is  not  thread safe, because it shares a return
       buffer across all threads, and many other functions in this library.

       Example: This function is intended to be used in a fashion  similar  to
       the following example:
              if (getgroups(data_size, data) < 0)
              {
                  fprintf(stderr, "%s\n", explain_getgroups(data_size, data));
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_getgroups_or_die(3) function.

   explain_errno_getgroups
       const char *explain_errno_getgroups(int errnum, int data_size, gid_t
       *data);

       The explain_errno_getgroups function is used to obtain  an  explanation
       of  an  error  returned by the getgroups(2) system call.  The least the
       message will contain is the value of strerror(errno),  but  usually  it
       will  do much better, and indicate the underlying cause in more detail.

       errnum  The error value to be decoded, usually obtained from the  errno
               global  variable  just  before this function is called. This is
               necessary if you need to call any code between the system  call
               to  be explained and this function, because many libc functions
               will alter the value of errno.

       data_size
               The original data_size, exactly as passed to  the  getgroups(2)
               system call.

       data    The original data, exactly as passed to the getgroups(2) system
               call.

       Returns:
               The message explaining the error. This message buffer is shared
               by  all  libexplain  functions  which do not supply a buffer in
               their argument list.  This will be overwritten by the next call
               to  any libexplain function which shares this buffer, including
               other threads.

       Note: This function is not thread safe,  because  it  shares  a  return
       buffer across all threads, and many other functions in this library.

       Example:  This  function is intended to be used in a fashion similar to
       the following example:
              if (getgroups(data_size, data) < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n", explain_errno_getgroups(err,
                  data_size, data));
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_getgroups_or_die(3) function.

   explain_message_getgroups
       void explain_message_getgroups(char *message, int message_size, int
       data_size, gid_t *data);

       The explain_message_getgroups function is used to obtain an explanation
       of an error returned by the getgroups(2) system call.   The  least  the
       message  will  contain  is the value of strerror(errno), but usually it
       will do much better, and indicate the underlying cause in more  detail.

       The  errno global variable will be used to obtain the error value to be
       decoded.

       message The location in which to  store  the  returned  message.  If  a
               suitable  message  return  buffer is supplied, this function is
               thread safe.

       message_size
               The size in bytes  of  the  location  in  which  to  store  the
               returned message.

       data_size
               The  original  data_size, exactly as passed to the getgroups(2)
               system call.

       data    The original data, exactly as passed to the getgroups(2) system
               call.

       Example:  This  function is intended to be used in a fashion similar to
       the following example:
              if (getgroups(data_size, data) < 0)
              {
                  char message[3000];
                  explain_message_getgroups(message, sizeof(message),
                  data_size, data);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_getgroups_or_die(3) function.

   explain_message_errno_getgroups
       void explain_message_errno_getgroups(char *message, int message_size,
       int errnum, int data_size, gid_t *data);

       The  explain_message_errno_getgroups  function  is  used  to  obtain an
       explanation of an error returned by the getgroups(2) system call.   The
       least  the  message  will  contain is the value of strerror(errno), but
       usually it will do much better, and indicate the  underlying  cause  in
       more detail.

       message The  location  in  which  to  store  the returned message. If a
               suitable message return buffer is supplied,  this  function  is
               thread safe.

       message_size
               The  size  in  bytes  of  the  location  in  which to store the
               returned message.

       errnum  The error value to be decoded, usually obtained from the  errno
               global  variable  just  before this function is called. This is
               necessary if you need to call any code between the system  call
               to  be explained and this function, because many libc functions
               will alter the value of errno.

       data_size
               The original data_size, exactly as passed to  the  getgroups(2)
               system call.

       data    The original data, exactly as passed to the getgroups(2) system
               call.

       Example: This function is intended to be used in a fashion  similar  to
       the following example:
              if (getgroups(data_size, data) < 0)
              {
                  int err = errno;
                  char message[3000];
                  explain_message_errno_getgroups(message, sizeof(message),
                  err, data_size, data);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_getgroups_or_die(3) function.

SEE ALSO

       getgroups(2)
               get/set list of supplementary group IDs

       explain_getgroups_or_die(3)
               get/set list of supplementary group IDs and report errors

COPYRIGHT

       libexplain version 0.19
       Copyright (C) 2009 Peter Miller

                                                          explain_getgroups(3)