explain_pwrite(3)

✨ explain_pwrite(3) ✨

okay bestie, welcome to the libexplain corner of the manual — this one lives in the Library Functions Manual and it's all about making pwrite(2) errors actually make sense instead of just yelling a cryptic number at you 💖

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🌸 NAME 🌸

explain_pwrite — explain pwrite(2) errors

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🎀 SYNOPSIS 🎀

#include <libexplain/pwrite.h>
const char *explain_pwrite(int fildes, const void *data, size_t
data_size, off_t offset);
const char *explain_errno_pwrite(int errnum, int fildes, const void
*data, size_t data_size, off_t offset);
void explain_message_pwrite(char *message, int message_size, int fildes,
const void *data, size_t data_size, off_t offset);
void explain_message_errno_pwrite(char *message, int message_size, int
errnum, int fildes, const void *data, size_t data_size, off_t offset);

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💅 DESCRIPTION 💅

These functions are your little translators for when pwrite(2) acts up 🫶 You call them, they hand you back an explanation of whatever error the system call threw at you. No cap.

🦋 explain_pwrite

const char *explain_pwrite(int fildes, const void *data, size_t
data_size, off_t offset);

The explain_pwrite function is how you get an explanation of an error that pwrite(2) returned. The least the message will contain is the value of strerror(errno), but usually it does so much better and tells you the actual underlying cause in more detail. it's giving detective energy 🔍

The errno global variable will be used to obtain the error value to be decoded.

• fildes — The original fildes, exactly as passed to the pwrite(2) system call. no edits, no glow-ups, the og.
• data — The original data, exactly as passed to the pwrite(2) system call.
• data_size — The original data_size, exactly as passed to the pwrite(2) system call.
• offset — The original offset, exactly as passed to the pwrite(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. so like… don't get attached to it 😭

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:

ssize_t result = pwrite(fildes, data, data_size, offset);
if (result < 0)
{
    fprintf(stderr, "%s\n", explain_pwrite(fildes, data,
    data_size, offset));
    exit(EXIT_FAILURE);
}

The above code example is available pre‐packaged as the explain_pwrite_or_die(3) function. slay, they did the work for you ✨

🌈 explain_errno_pwrite

const char *explain_errno_pwrite(int errnum, int fildes, const void
*data, size_t data_size, off_t offset);

The explain_errno_pwrite function is used to obtain an explanation of an error returned by the pwrite(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. yeah bestie, errno is fickle like that 🙈
• fildes — The original fildes, exactly as passed to the pwrite(2) system call.
• data — The original data, exactly as passed to the pwrite(2) system call.
• data_size — The original data_size, exactly as passed to the pwrite(2) system call.
• offset — The original offset, exactly as passed to the pwrite(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:

ssize_t result = pwrite(fildes, data, data_size, offset);
if (result < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_pwrite(err, fildes,
    data, data_size, offset));
    exit(EXIT_FAILURE);
}

The above code example is available pre‐packaged as the explain_pwrite_or_die(3) function.

⭐ explain_message_pwrite

void explain_message_pwrite(char *message, int message_size, int fildes,
const void *data, size_t data_size, off_t offset);

The explain_message_pwrite function is used to obtain an explanation of an error returned by the pwrite(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. 👑 (yes, you read that right, you brought your own buffer, you get thread safety)
• 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 pwrite(2) system call.
• data — The original data, exactly as passed to the pwrite(2) system call.
• data_size — The original data_size, exactly as passed to the pwrite(2) system call.
• offset — The original offset, exactly as passed to the pwrite(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:

ssize_t result = pwrite(fildes, data, data_size, offset);
if (result < 0)
{
    char message[3000];
    explain_message_pwrite(message, sizeof(message), fildes,
    data, data_size, offset);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre‐packaged as the explain_pwrite_or_die(3) function.

💜 explain_message_errno_pwrite

void explain_message_errno_pwrite(char *message, int message_size, int
errnum, int fildes, const void *data, size_t data_size, off_t offset);

The explain_message_errno_pwrite function is used to obtain an explanation of an error returned by the pwrite(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.
• fildes — The original fildes, exactly as passed to the pwrite(2) system call.
• data — The original data, exactly as passed to the pwrite(2) system call.
• data_size — The original data_size, exactly as passed to the pwrite(2) system call.
• offset — The original offset, exactly as passed to the pwrite(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:

ssize_t result = pwrite(fildes, data, data_size, offset);
if (result < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_pwrite(message, sizeof(message), err,
    fildes, data, data_size, offset);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre‐packaged as the explain_pwrite_or_die(3) function.

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👀 SEE ALSO 👀

• pwrite(2) — read from or write to a file descriptor at a given offset
• explain_pwrite_or_die(3) — read from or write to a file descriptor at a given offset and report errors

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🍓 COPYRIGHT 🍓

libexplain version 1.4 Copyright (C) 2009 Peter Miller

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and that's the whole page bestie, you ate it up 💖 this was explain_pwrite(3) from libexplain version 1.4, copyright (C) 2009 Peter Miller — go forth and explain those errors, mwah 🫶✨👑