explain_gethostname(3)

💖 explain_gethostname — bestie edition 💖

okay so this is a page from the Library Functions Manual, and it's all about explain_gethostname(3), which is a lil library function that explains the errors you get from gethostname(2). yes the naming is a whole vibe. let's go 🦋

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✨ NAME ✨

explain_gethostname — explain gethostname(2) errors

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🌸 SYNOPSIS 🌸

#include <libexplain/gethostname.h>
const char *explain_gethostname(char *data, size_t data_size);
const char *explain_errno_gethostname(int errnum, char *data, size_t data_size);
void explain_message_gethostname(char *message, int message_size, char *data, size_t data_size);
void explain_message_errno_gethostname(char *message, int message_size, int errnum, char *data, size_t data_size);

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💅 DESCRIPTION 💅

so basically, these functions exist so you can get actual explanations for errors that the gethostname(2) system call throws back at you. it's giving "translator for your cryptic syscall fails". iconic behavior honestly.

🎀 explain_gethostname

const char *explain_gethostname(char *data, size_t data_size);

explain_gethostname is the one you call to get an explanation of an error returned by the gethostname(2) system call. the least the message will contain is the value of strerror(errno) — but usually it goes so much harder than that and tells you the underlying cause in way more detail. no cap.

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

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

if (gethostname(data, data_size) < 0)
{
    fprintf(stderr, "%s\n", explain_gethostname(data, data_size));
    exit(EXIT_FAILURE);
}

that code example above is available pre-packaged as the explain_gethostname_or_die(3) function. cute right? 🫶

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

Returns: the message explaining the error. this message buffer is shared by all libexplain functions that don't supply a buffer in their argument list. it will get overwritten by the next call to any libexplain function that shares this buffer — including other threads. so like, don't get attached to it bestie, it's not yours 💀

Note: this function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library do the same. periodt.

🧚 explain_errno_gethostname

const char *explain_errno_gethostname(int errnum, char *data, size_t data_size);

explain_errno_gethostname is the one you call to get an explanation of an error returned by the gethostname(2) system call. again, the least the message will contain is the value of strerror(errno), but usually it does way better and points at the underlying cause in more detail. slay.

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

if (gethostname(data, data_size) < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_gethostname(err, data, data_size));
    exit(EXIT_FAILURE);
}

the above code example is available pre-packaged as the explain_gethostname_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. like they're messy, okay 😭
• data — the original data, exactly as passed to the gethostname(2) system call.
• data_size — the original data_size, exactly as passed to the gethostname(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 too. 💀

🍓 explain_message_gethostname

void explain_message_gethostname(char *message, int message_size, char *data, size_t data_size);

explain_message_gethostname is used to obtain an explanation of an error returned by the gethostname(2) system call. 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 (gethostname(data, data_size) < 0)
{
    char message[3000];
    explain_message_gethostname(message, sizeof(message), data, data_size);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

the above code example is available pre-packaged as the explain_gethostname_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. main character energy, honestly 👑
• message_size — the size in bytes of the location in which to store the returned message.
• data — the original data, exactly as passed to the gethostname(2) system call.
• data_size — the original data_size, exactly as passed to the gethostname(2) system call.

💜 explain_message_errno_gethostname

void explain_message_errno_gethostname(char *message, int message_size, int errnum, char *data, size_t data_size);

explain_message_errno_gethostname is used to obtain an explanation of an error returned by the gethostname(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.

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

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

the above code example is available pre-packaged as the explain_gethostname_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.
• data — the original data, exactly as passed to the gethostname(2) system call.
• data_size — the original data_size, exactly as passed to the gethostname(2) system call.

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🌈 SEE ALSO 🌈

• gethostname(2) — get/set hostname
• explain_gethostname_or_die(3) — get/set hostname 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 that read 💅✨ shoutout to libexplain version 1.4 and Copyright (C) 2009 Peter Miller for making this possible, mwah 🎀💖🦋