explain_gethostbyname(3)

💖 explain_gethostbyname(3) 💖

okay bestie, gather round, because this is the libexplain glow-up for gethostbyname(3) errors and it's honestly so underrated. it lives in the Library Functions Manual, it's the moment, it's the vibe. ✨

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🌸 NAME 🌸

explain_gethostbyname — explain gethostbyname(3) errors. that's it, that's the job, and she does it flawlessly. 💅

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🎀 SYNOPSIS 🎀

#include <libexplain/gethostbyname.h>
const char *explain_gethostbyname(const char *name);
const char *explain_errno_gethostbyname(int errnum, const char *name);
void explain_message_gethostbyname(char *message, int message_size,
const char *name);
void explain_message_errno_gethostbyname(char *message, int
message_size, int errnum, const char *name);

like, four whole functions. a whole girlboss squad. 🫶

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🦋 DESCRIPTION 🦋

so the tea is: these functions are how you get explanations for errors that gethostbyname(3) threw back at you. the system call is messy, the error messages don't have to be. 💖

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✨ explain_gethostbyname ✨

const char *explain_gethostbyname(const char *name);

this one is your go-to. you call it, it gives you an explanation of an error returned by the gethostbyname(3) system call. the bare minimum you'll get is the value of strerror(errno) — but ngl, it usually does so much better than that, and it'll point at the actual underlying cause in more detail. it ate. 👑

the errno global variable is what it peeks at to grab the error value it's gonna decode. no cap.

• name — the original name, exactly as passed to the gethostbyname(3) system call. don't get cute with it, pass it as-is. 🙈

Returns:

the message explaining the error. ⚠️ big warning though: this message buffer is shared by every libexplain function that doesn't take a buffer in its argument list. so it will get overwritten by the next call to any libexplain function that shares this buffer — including calls from other threads. it's giving "one communal hairbrush", bestie.

Note: this function is not thread safe, because it shares a return buffer across all threads, and so do many other functions in this library. fr fr, be careful. 😭

Example: this function is meant to be used in a fashion similar to this:

struct hostent *result = gethostbyname(name);
if (!result)
{
    fprintf(stderr, "%s\n", explain_gethostbyname(name));
    exit(EXIT_FAILURE);
}

and the way that this exact code example is already available pre-packaged as the explain_gethostbyname_or_die(3) function? iconic. you don't even have to write it yourself. 🎀

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💜 explain_errno_gethostbyname 💜

const char *explain_errno_gethostbyname(int errnum, const char *name);

same energy as above, but this one lets you hand it the error value yourself. you use it to obtain an explanation of an error returned by the gethostbyname(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. she's thorough. 💅

• errnum — the error value to be decoded, usually grabbed from the errno global variable right before you call this function. this matters if you need to run any code between the system call you're explaining and this function, because a lot of libc functions will mess with the value of errno. so snatch it early. 🫶
• name — the original name, exactly as passed to the gethostbyname(3) system call.

Returns:

the message explaining the error. same deal as before: this message buffer is shared by all libexplain functions that don't supply a buffer in their argument list, and it'll be overwritten by the next call to any libexplain function sharing that buffer — other threads included. 😭

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

Example: meant to be used in a fashion similar to this:

struct hostent *result = gethostbyname(name);
if (!result)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_gethostbyname(err,
    name));
    exit(EXIT_FAILURE);
}

and yes, this code example is also pre-packaged as the explain_gethostbyname_or_die(3) function. slay. ✨

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🌈 explain_message_gethostbyname 🌈

void explain_message_gethostbyname(char *message, int message_size,
const char *name);

this one's the bring-your-own-buffer version and honestly? main character energy. it obtains an explanation of an error returned by the gethostbyname(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.

• message — the location where the returned message gets stored. 💡 if you supply a suitable message return buffer, this function is thread safe. look at her go!! 👑
• message_size — the size in bytes of the location where the returned message gets stored.
• name — the original name, exactly as passed to the gethostbyname(3) system call.

Example: meant to be used in a fashion similar to this:

struct hostent *result = gethostbyname(name);
if (!result)
{
    char message[3000];
    explain_message_gethostbyname(message, sizeof(message),
    name);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

and (say it with me) this code example is pre-packaged as the explain_gethostbyname_or_die(3) function. 🎀

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🍓 explain_message_errno_gethostbyname 🍓

void explain_message_errno_gethostbyname(char *message, int
message_size, int errnum, const char *name);

the final boss: your own buffer and your own errno. it obtains an explanation of an error returned by the gethostbyname(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. 🌸

• message — the location where the returned message gets stored. if you supply a suitable message return buffer, this function is thread safe. ✨
• message_size — the size in bytes of the location where the returned message gets stored.
• errnum — the error value to be decoded, usually obtained from the errno global variable just before this function is called. necessary if you need to call any code between the system call being explained and this function, because many libc functions will alter the value of errno. ⚠️
• name — the original name, exactly as passed to the gethostbyname(3) system call.

Example: meant to be used in a fashion similar to this:

struct hostent *result = gethostbyname(name);
if (!result)
{
    int err = errno;
    char message[3000];
    explain_message_errno_gethostbyname(message, sizeof(message),
    err, name);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

and the above code example is available pre-packaged as the explain_gethostbyname_or_die(3) function. periodt. 💅

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👑 SEE ALSO 👑

• gethostbyname(3) — get host address given host name
• explain_gethostbyname_or_die(3) — get host address given host name and report errors

go read those too, bestie, iykyk. 🦋

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💖 COPYRIGHT 💖

libexplain version 1.4 Copyright (C) 2013 Peter Miller

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and that's the whole page, my love — libexplain version 1.4, Copyright (C) 2013 Peter Miller, written up all cute for you. go explain some errors and thrive. mwah. 💅💖🎀🦋🌸