Provided by: libexplain-dev_1.4.D001-13_amd64 
NAME
explain_fcntl - explain fcntl(2) errors
SYNOPSIS
#include <libexplain/fcntl.h>
const char *explain_fcntl(int fildes, int command, long arg);
const char *explain_errno_fcntl(int errnum, int fildes, int command, long arg);
void explain_message_fcntl(char *message, int message_size, int fildes, int command, long arg);
void explain_message_errno_fcntl(char *message, int message_size, int errnum, int fildes, int command,
long arg);
DESCRIPTION
These functions may be used to obtain explanations for errors returned by the fcntl(2) system call.
explain_fcntl
const char *explain_fcntl(int fildes, int command, long arg);
The explain_fcntl function is used to obtain an explanation of an error returned by the fcntl(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.
This function is intended to be used in a fashion similar to the following example:
if (fcntl(fildes, command, arg) < 0)
{
fprintf(stderr, "%s\n", explain_fcntl(fildes, command, arg));
exit(EXIT_FAILURE);
}
fildes The original fildes, exactly as passed to the fcntl(2) system call.
command The original command, exactly as passed to the fcntl(2) system call.
arg The original arg, exactly as passed to the fcntl(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.
explain_errno_fcntl
const char *explain_errno_fcntl(int errnum, int fildes, int command, long arg);
The explain_errno_fcntl function is used to obtain an explanation of an error returned by the fcntl(2)
system call. The least the message will contain is the value of strerror(errnum), but usually it will do
much better, and indicate the underlying cause in more detail.
This function is intended to be used in a fashion similar to the following example:
if (fcntl(fildes, command, arg) < 0)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_fcntl(err, fildes, command, arg));
exit(EXIT_FAILURE);
}
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.
fildes The original fildes, exactly as passed to the fcntl(2) system call.
command The original command, exactly as passed to the fcntl(2) system call.
arg The original arg, exactly as passed to the fcntl(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.
explain_message_fcntl
void explain_message_fcntl(char *message, int message_size, int fildes, int command, long arg);
The explain_message_fcntl function may be used to obtain an explanation of an error returned by the
fcntl(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.
This function is intended to be used in a fashion similar to the following example:
if (fcntl(fildes, command, arg) < 0)
{
char message[3000];
explain_message_fcntl(message, sizeof(message), fildes, command, arg);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
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.
fildes The original fildes, exactly as passed to the fcntl(2) system call.
command The original command, exactly as passed to the fcntl(2) system call.
arg The original arg, exactly as passed to the fcntl(2) system call.
explain_message_errno_fcntl
void explain_message_errno_fcntl(char *message, int message_size, int errnum, int fildes, int command,
long arg);
The explain_message_errno_fcntl function may be used to obtain an explanation of an error returned by the
fcntl(2) system call. The least the message will contain is the value of strerror(errnum), but usually
it will do much better, and indicate the underlying cause in more detail.
This function is intended to be used in a fashion similar to the following example:
if (fcntl(fildes, command, arg) < 0)
{
int err = errno;
char message[3000];
explain_message_errno_fcntl(message, sizeof(message), err, fildes,
command, arg);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
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.
fildes The original fildes, exactly as passed to the fcntl(2) system call.
command The original command, exactly as passed to the fcntl(2) system call.
arg The original arg, exactly as passed to the fcntl(2) system call.
SEE ALSO
fcntl(2)
manipulate a file descriptor
explain_fcntl_or_die(3)
manipulate a file descriptor and report errors
COPYRIGHT
libexplain version 1.4
Copyright (C) 2008 Peter Miller
explain_fcntl(3)