Provided by: libexplain-dev_1.4.D001-7_amd64 
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)