explain_setsockopt(3)

💖 explain_setsockopt — the manual page, but make it make sense 💖

okay so this is explain_setsockopt(3) from the Library Functions Manual, bestie. it lives in libexplain and its whole job is to explain setsockopt(2) errors like the group chat member who actually read the docs. 🫶

---

✨ NAME ✨

explain_setsockopt — explain setsockopt(2) errors 💅

---

🌸 SYNOPSIS 🌸

#include <libexplain/setsockopt.h>
const char *explain_setsockopt(int fildes, int level, int name, void
*data, socklen_t data_size);
const char *explain_errno_setsockopt(int errnum, int fildes, int level,
int name, void *data, socklen_t data_size);
void explain_message_setsockopt(char *message, int message_size, int
fildes, int level, int name, void *data, socklen_t data_size);
void explain_message_errno_setsockopt(char *message, int message_size,
int errnum, int fildes, int level, int name, void *data, socklen_t
data_size);

---

🦋 DESCRIPTION 🦋

these functions? iconic. they hand you explanations for errors that the setsockopt(2) system call throws back at you. no more squinting at a bare error number wondering what went wrong — this library literally tells you. ✨

💜 explain_setsockopt

const char *explain_setsockopt(int fildes, int level, int name, void
*data, socklen_t data_size);

the explain_setsockopt function gets you an explanation of an error returned by the setsockopt(2) system call. the least it'll give you is the value of strerror(errno), but usually it does so much better and points at the underlying cause in more detail. it's giving detective energy fr fr 🔍

the errno global variable is what's used to grab the error value that gets decoded.

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

if (setsockopt(fildes, level, name, data, data_size) < 0)
{
    fprintf(stderr, "%s\n", explain_setsockopt(fildes,
        level, name, data, data_size));
    exit(EXIT_FAILURE);
}

the above code example is available pre‐packaged as the explain_setsockopt_or_die(3) function. 🎀

• fildes — the original fildes, exactly as passed to the setsockopt(2) system call.
• level — the original level, exactly as passed to the setsockopt(2) system call.
• name — the original name, exactly as passed to the setsockopt(2) system call.
• data — the original data, exactly as passed to the setsockopt(2) system call.
• data_size — the original data_size, exactly as passed to the setsockopt(2) system call.

Returns:

the message explaining the error. heads up though: this message buffer is shared by all libexplain functions that don't supply a buffer in their argument list. it gets overwritten by the next call to any libexplain function that 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. periodt.

🧚 explain_errno_setsockopt

const char *explain_errno_setsockopt(int errnum, int fildes, int level,
int name, void *data, socklen_t data_size);

the explain_errno_setsockopt function is used to obtain an explanation of an error returned by the setsockopt(2) system call. the least the message will contain is the value of strerror(errnum), but usually it does much better and indicates the underlying cause in more detail. 💖

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

if (setsockopt(fildes, level, name, data, data_size) < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_setsockopt(err,
        fildes, level, name, data, data_size));
    exit(EXIT_FAILURE);
}

the above code example is available pre‐packaged as the explain_setsockopt_or_die(3) function. 🌈

• 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. lowkey important.
• fildes — the original fildes, exactly as passed to the setsockopt(2) system call.
• level — the original level, exactly as passed to the setsockopt(2) system call.
• name — the original name, exactly as passed to the setsockopt(2) system call.
• data — the original data, exactly as passed to the setsockopt(2) system call.
• data_size — the original data_size, exactly as passed to the setsockopt(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.

🎀 explain_message_setsockopt

void explain_message_setsockopt(char *message, int message_size, int
fildes, int level, int name, void *data, socklen_t data_size);

the explain_message_setsockopt function may be used to obtain an explanation of an error returned by the setsockopt(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. slay. ✨

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 (setsockopt(fildes, level, name, data, data_size) < 0)
{
    char message[3000];
    explain_message_setsockopt(message, sizeof(message),
        fildes, level, name, data, data_size);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

the above code example is available pre‐packaged as the explain_setsockopt_or_die(3) function. 💅

• message — the location in which to store the returned message. if a suitable message return buffer is supplied, this function is thread safe. we love that for us.
• 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 setsockopt(2) system call.
• level — the original level, exactly as passed to the setsockopt(2) system call.
• name — the original name, exactly as passed to the setsockopt(2) system call.
• data — the original data, exactly as passed to the setsockopt(2) system call.
• data_size — the original data_size, exactly as passed to the setsockopt(2) system call.

🍓 explain_message_errno_setsockopt

void explain_message_errno_setsockopt(char *message, int message_size,
int errnum, int fildes, int level, int name, void *data, socklen_t
data_size);

the explain_message_errno_setsockopt function may be used to obtain an explanation of an error returned by the setsockopt(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:

if (setsockopt(fildes, level, name, data, data_size) < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_setsockopt(message, sizeof(message),
        err, fildes, level, name, data, data_size);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

the above code example is available pre‐packaged as the explain_setsockopt_or_die(3) function. 👑

• 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 setsockopt(2) system call.
• level — the original level, exactly as passed to the setsockopt(2) system call.
• name — the original name, exactly as passed to the setsockopt(2) system call.
• data — the original data, exactly as passed to the setsockopt(2) system call.
• data_size — the original data_size, exactly as passed to the setsockopt(2) system call.

---

🌈 SEE ALSO 🌈

• setsockopt(2) — get and set options on sockets
• explain_setsockopt_or_die(3) — get and set options on sockets and report errors

---

💜 COPYRIGHT 💜

libexplain version 1.4 Copyright (C) 2009 Peter Miller

---

and that's the whole page bestie, no notes. it came from libexplain version 1.4, © 2009 Peter Miller, straight out of the Library Functions Manual, and it's filed under explain_setsockopt(3). go forth and decode those socket errors like the main character you are. 💅✨🦋