explain_open(3)

NAME
explain_open - explain open(2) errors

SYNOPSIS
#include <libexplain/open.h>
const char *explain_open(const char *pathname, int flags, int mode);
const char *explain_errno_open(int errnum, const char *pathname, int flags, int mode);
void explain_message_open(char *message, int message_size, const char *pathname, int flags, int mode);
void explain_message_errno_open(char *message, int message_size, int errnum, const char *pathname, int flags, int mode);

DESCRIPTION
These functions may be used to obtains explanations for open(2) errors.

  explain_open(const char *pathname, int flags, int mode);
const char *explain_open(const char *pathname, int flags, int mode);

The explain_open function is used to obtain an explanation of an error returned by the open(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:
    int fd = open(pathname, flags, mode);
    if (fd < 0)
    {
        fprintf(stderr, '%s, explain_open(pathname, flags, mode));
        exit(EXIT_FAILURE);
    }

pathname
    The original pathname, exactly as passed to the open(2) system call.

flags
    The original flags, exactly as passed to the open(2) system call.

mode
    The original mode, exactly as passed to the open(2) system call (or zero if the original call didn't need a mode argument).

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_open
const char *explain_errno_open(int errnum, const char *pathname, int flags, int mode);

The explain_errno_open function is used to obtain an explanation of an error returned by the open(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:
    int fd = open(pathname, flags, mode);
    if (fd < 0)
    {
        int err = errno;
        fprintf(stderr, '%s, explain_errno_open(err, pathname,
            flags, mode));
        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.

pathname
    The original pathname, exactly as passed to the open(2) system call.

flags
    The original flags, exactly as passed to the open(2) system call.

mode
    The original mode, exactly as passed to the open(2) system call (or zero if the original call didn't need a mode argument).

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_open
void explain_message_open(char *message, int message_size, const char *pathname, int flags, int mode);

The explain_message_open function is used to obtain an explanation of an error returned by the open(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:
    int fd = open(pathname, flags, mode);
    if (fd < 0)
    {
        char message[3000];
        explain_message_open(message, sizeof(message), pathname, flags,
            mode);
        fprintf(stderr, '%s, message);
        exit(EXIT_FAILURE);
    }

message
    The location in which to store the returned message. Because a message return buffer has been supplied, this function is thread safe.

message_size
    The size in bytes of the location in which to store the returned message.

pathname
    The original pathname, exactly as passed to the open(2) system call.

flags
    The original flags, exactly as passed to the open(2) system call.

mode
    The original mode, exactly as passed to the open(2) system call (or zero if the original call didn't need a mode argument).

  explain_message_errno_open
void explain_message_errno_open(char *message, int message_size, int errnum, const char *pathname, int flags, int mode);

The explain_message_errno_open function is used to obtain an explanation of an error returned by the open(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 exameple:
    int fd = open(pathname, flags, mode);
    if (fd < 0)
    {
        int err = errno;
        char message[3000];
        explain_message_errno_open(message, sizeof(message), err, pathname,
            flags, mode);
        fprintf(stderr, '%s, message);
        exit(EXIT_FAILURE);
    }

message
    The location in which to store the returned message. Because a message return buffer has been 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.

pathname
    The original pathname, exactly as passed to the open(2) system call.

flags
    The original flags, exactly as passed to the open(2) system call.

mode
    The original mode, exactly as passed to the open(2) system call (or zero if the original call didn't need a mode argument).

COPYRIGHT
libexplain version 1.4
Copyright (C) 2008 Peter Miller

AUTHOR
Written by Peter Miller <pmiller@opensource.org.au>