explain_dirfd(3)

💖 explain_dirfd(3) — the manual page, but make it make sense 💖

okay bestie, so this is a page from the Library Functions Manual, and the whole point of it is: you called dirfd(3), it broke, and now you're sitting there like "why 😭". This page is the glow-up. It explains how to get the why.

---

✨ NAME ✨

explain_dirfd — the one that explains your dirfd(3) errors 🫶

---

✨ SYNOPSIS ✨

#include <libexplain/dirfd.h>
const char *explain_dirfd(DIR *dir);
const char *explain_errno_dirfd(int errnum, DIR *dir);
void explain_message_dirfd(char *message, int message_size, DIR *dir);
void explain_message_errno_dirfd(char *message, int message_size, int
errnum, DIR *dir);

---

✨ DESCRIPTION ✨

So like. These functions are your little translators 💅 you use them to get explanations for errors that the dirfd(3) system call returned. That's it, that's the job. Four of them, each with a slightly different vibe depending on how much control you want.

---

🌸 explain_dirfd 🌸

const char *explain_dirfd(DIR *dir);

The explain_dirfd function gets you an explanation of an error returned by the dirfd(3) system call. The least the message will contain is the value of strerror(errno) — but usually it does so much better than that and tells you the actual underlying cause in more detail. she ate.

The errno global variable is what gets used to obtain the error value to be decoded.

• dir — the original dir, exactly as passed to the dirfd(3) system call. no edits, no remixing, the og.

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, be careful out there bestie 💀

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

int result = dirfd(dir);
if (result < 0)
{
    fprintf(stderr, "%s\n", explain_dirfd(dir));
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_dirfd_or_die(3) function. 🎀

---

🌈 explain_errno_dirfd 🌈

const char *explain_errno_dirfd(int errnum, DIR *dir);

The explain_errno_dirfd function gets you an explanation of an error returned by the dirfd(3) system call. Again, 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. iconic behavior fr fr.

• 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. like, they will literally change it on you, no cap.
• dir — the original dir, exactly as passed to the dirfd(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.

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

int result = dirfd(dir);
if (result < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_dirfd(err, dir));
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_dirfd_or_die(3) function. ✨

---

🦋 explain_message_dirfd 🦋

void explain_message_dirfd(char *message, int message_size, DIR *dir);

The explain_message_dirfd function gets you an explanation of an error returned by the dirfd(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. yes queen, 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. 🫶 look at her go
• message_size — the size in bytes of the location in which to store the returned message.
• dir — the original dir, exactly as passed to the dirfd(3) system call.

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

int result = dirfd(dir);
if (result < 0)
{
    char message[3000];
    explain_message_dirfd(message, sizeof(message), dir);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_dirfd_or_die(3) function. 💜

---

🧚 explain_message_errno_dirfd 🧚

void explain_message_errno_dirfd(char *message, int message_size, int
errnum, DIR *dir);

The explain_message_errno_dirfd function gets you an explanation of an error returned by the dirfd(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. main character energy tbh.

• 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.
• dir — the original dir, exactly as passed to the dirfd(3) system call.

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

int result = dirfd(dir);
if (result < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_dirfd(message, sizeof(message), err,
    dir);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_dirfd_or_die(3) function. 🌸

---

✨ SEE ALSO ✨

• dirfd(3) — get directory stream file descriptor
• explain_dirfd_or_die(3) — get directory stream file descriptor and report errors

---

✨ COPYRIGHT ✨

libexplain version 1.4 Copyright (C) 2009 Peter Miller

---

and that's the whole page bestie, you're officially literate in explain_dirfd(3) 💖 go forth and get actual explanations instead of vibes-based debugging, periodt. 🌈⭐👑