explain_fwrite(3)

💖 explain_fwrite — okay bestie, let's decode some fwrite(3) errors 💖

So like, this is the manual page for the explain_fwrite family of functions, living in section 3 of the manual. It's giving "error translator" energy: you give it the exact same args you gave to fwrite(3), and it hands you back a human-readable explanation of what went wrong. No cap. 🦋

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✨ NAME ✨

explain_fwrite — explain fwrite(3) errors 💅

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🌸 SYNOPSIS 🌸

#include <libexplain/fwrite.h>
const char *explain_fwrite(const void *ptr, size_t size, size_t nmemb,
FILE *fp);
const char *explain_errno_fwrite(int errnum, const void *ptr, size_t
size, size_t nmemb, FILE *fp);
void explain_message_fwrite(char *message, int message_size, const void
*ptr, size_t size, size_t nmemb, FILE *fp);
void explain_message_errno_fwrite(char *message, int message_size, int
errnum, const void *ptr, size_t size, size_t nmemb, FILE *fp);

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👑 DESCRIPTION 👑

These functions may be used to obtain explanations for errors returned by the fwrite(3) system call. That's it, that's the whole job. 🎀

🧚 explain_fwrite

const char *explain_fwrite(const void *ptr, size_t size, size_t nmemb,
FILE *fp);

The explain_fwrite function is used to obtain an explanation of an error returned by the fwrite(3) 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. It's not just reading you the error code, it's giving you lore. 😭

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 (fwrite(ptr, size, nmemb, fp) < 0)
{
    fprintf(stderr, "%s\n", explain_fwrite(ptr, size, nmemb, fp));
    exit(EXIT_FAILURE);
}

• ptr — The original ptr, exactly as passed to the fwrite(3) system call.
• size — The original size, exactly as passed to the fwrite(3) system call.
• nmemb — The original nmemb, exactly as passed to the fwrite(3) system call.
• fp — The original fp, exactly as passed to the fwrite(3) 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. So like… one at a time, bestie. 💀

🌈 explain_errno_fwrite

const char *explain_errno_fwrite(int errnum, const void *ptr, size_t
size, size_t nmemb, FILE *fp);

The explain_errno_fwrite function is used to obtain an explanation of an error returned by the fwrite(3) 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 (fwrite(ptr, size, nmemb, fp) < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_fwrite(err,
        ptr, size, nmemb, fp));
    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. (Yes queen, errno is fragile, grab it early. 🙈)
• ptr — The original ptr, exactly as passed to the fwrite(3) system call.
• size — The original size, exactly as passed to the fwrite(3) system call.
• nmemb — The original nmemb, exactly as passed to the fwrite(3) system call.
• fp — The original fp, exactly as passed to the fwrite(3) 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_fwrite

void explain_message_fwrite(char *message, int message_size, const void
*ptr, size_t size, size_t nmemb, FILE *fp);

The explain_message_fwrite function may be used to obtain an explanation of an error returned by the fwrite(3) 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 (fwrite(ptr, size, nmemb, fp) < 0)
{
    char message[3000];
    explain_message_fwrite(message, sizeof(message), ptr, size, nmemb, fp);
    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. Slay.
• message_size — The size in bytes of the location in which to store the returned message.
• ptr — The original ptr, exactly as passed to the fwrite(3) system call.
• size — The original size, exactly as passed to the fwrite(3) system call.
• nmemb — The original nmemb, exactly as passed to the fwrite(3) system call.
• fp — The original fp, exactly as passed to the fwrite(3) system call.

💜 explain_message_errno_fwrite

void explain_message_errno_fwrite(char *message, int message_size, int
errnum, const void *ptr, size_t size, size_t nmemb, FILE *fp);

The explain_message_errno_fwrite function may be used to obtain an explanation of an error returned by the fwrite(3) 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 (fwrite(ptr, size, nmemb, fp) < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_fwrite(message, sizeof(message), err,
        ptr, size, nmemb, fp);
    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.
• ptr — The original ptr, exactly as passed to the fwrite(3) system call.
• size — The original size, exactly as passed to the fwrite(3) system call.
• nmemb — The original nmemb, exactly as passed to the fwrite(3) system call.
• fp — The original fp, exactly as passed to the fwrite(3) system call.

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🫶 SEE ALSO 🫶

• fwrite(3) — binary stream output
• explain_fwrite_or_die(3) — binary stream output and report errors

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💖 COPYRIGHT 💖

libexplain version 1.4 Copyright (C) 2008 Peter Miller

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And that's the whole page, bestie — thanks for reading all the way to the end, you're literally the main character. ✨ This was explain_fwrite(3) from libexplain version 1.4, dated 2008 (Copyright (C) 2008 Peter Miller) — mwah, take care of your errno, drink water, and go write some bytes. 💅🎀🦋