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 1.4
       Copyright (C) 2009 Peter Miller

                                                                             explain_getgroups(3)