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Man Pages


Manual Reference Pages  -  EXPLAIN_OPEN (3)

NAME

explain_open - explain open(2) errors

CONTENTS

Synopsis
Description
Copyright
Author

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 I]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 I]open(2) system call. The least the message will contain is the value of CW]strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The I]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, ’%s0, explain_open(pathname, flags, mode));
    exit(EXIT_FAILURE);
}

I]pathname
  The original pathname, exactly as passed to the I]open(2) system call.
I]flags The original flags, exactly as passed to the I]open(2) system call.
I]mode The original mode, exactly as passed to the I]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.
B]Note: This function is B]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 I]open(2) system call. The least the message will contain is the value of CW]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, ’%s0, explain_errno_open(err, pathname,
        flags, mode));
    exit(EXIT_FAILURE);
}

I]errnum The error value to be decoded, usually obtained from the I]errno global variable just before this function is called. This is necessary if you need to call B]any code between the system call to be explained and this function, because many libc functions will alter the value of I]errno.
I]pathname
  The original pathname, exactly as passed to the I]open(2) system call.
I]flags The original flags, exactly as passed to the I]open(2) system call.
I]mode The original mode, exactly as passed to the I]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.
B]Note: This function is B]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 I]open(2) system call. The least the message will contain is the value of CW]strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The I]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, ’%s0, message);
    exit(EXIT_FAILURE);
}

I]message
  The location in which to store the returned message. Because a message return buffer has been supplied, this function is thread safe.
I]message_size
  The size in bytes of the location in which to store the returned message.
I]pathname
  The original pathname, exactly as passed to the I]open(2) system call.
I]flags The original flags, exactly as passed to the I]open(2) system call.
I]mode The original mode, exactly as passed to the I]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 I]open(2) system call. The least the message will contain is the value of CW]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, ’%s0, message);
    exit(EXIT_FAILURE);
}

I]message
  The location in which to store the returned message. Because a message return buffer has been supplied, this function is thread safe.
I]message_size
  The size in bytes of the location in which to store the returned message.
I]errnum The error value to be decoded, usually obtained from the I]errno global variable just before this function is called. This is necessary if you need to call B]any code between the system call to be explained and this function, because many libc functions will alter the value of I]errno.
I]pathname
  The original pathname, exactly as passed to the I]open(2) system call.
I]flags The original flags, exactly as passed to the I]open(2) system call.
I]mode The original mode, exactly as passed to the I]open(2) system call (or zero if the original call didn’t need a mode argument).

COPYRIGHT

libexplain version 1.3
Copyright © 2008 Peter Miller

AUTHOR

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