Poster of Linux kernelThe best gift for a Linux geek
explain_getgroups

explain_getgroups

Section: C Library Functions (3)
Local index Up
 

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 0.37
Copyright (C) 2009 Peter Miller


 

Index

NAME
SYNOPSIS
DESCRIPTION
explain_getgroups
explain_errno_getgroups
explain_message_getgroups
explain_message_errno_getgroups
SEE ALSO
COPYRIGHT

This document was created by man2html, using the manual pages.
Time: 21:45:49 GMT, April 16, 2011