explain_fcntl(3)

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 0.46
Copyright (C) 2008 Peter Miller