explain_unsetenv(3)

💖 explain_unsetenv(3) 💖

okay bestie, so this is a page from the Library Functions Manual, and it's literally all about the explain_unsetenv crew — the little functions that tell you why unsetenv(3) said no. no cap. 🫶

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✨ NAME ✨

explain_unsetenv — explain unsetenv(3) errors 💅

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🌸 SYNOPSIS 🌸

#include <libexplain/unsetenv.h>
const char *explain_unsetenv(const char *name);
const char *explain_errno_unsetenv(int errnum, const char *name);
void explain_message_unsetenv(char *message, int message_size, const char *name);
void explain_message_errno_unsetenv(char *message, int message_size, int errnum, const char *name);

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🦋 DESCRIPTION 🦋

so these functions? they're the ones you call to get actual explanations for errors that unsetenv(3) hands back to you. like, the system call misbehaves and you're just standing there like 🧍 — nah, these have your back.

🌈 explain_unsetenv

const char *explain_unsetenv(const char *name);

explain_unsetenv is your go-to for getting an explanation of an error that unsetenv(3) returned. the least the message will contain is the value of strerror(errno), but honestly? usually it does so much better and points at the actual underlying cause in more detail. it's giving detective energy. 🔍

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

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

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 will get overwritten by the next call to any libexplain function that shares this buffer — including calls from other threads. 😭

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. periodt.

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

if (unsetenv(name) < 0)
{
    fprintf(stderr, "%s\n", explain_unsetenv(name));
    exit(EXIT_FAILURE);
}

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

💜 explain_errno_unsetenv

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

explain_errno_unsetenv is used to obtain an explanation of an error returned by the unsetenv(3) system call. the least the message will contain is the value of strerror(errno), but usually it does much better and indicates the underlying cause in more detail. iconic. ✨

• errnum — the error value to be decoded, usually grabbed from the errno global variable right before this function is called. this is 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. so like, save it first, bestie. 🙈
• name — the original name, exactly as passed to the unsetenv(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:

if (unsetenv(name) < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_unsetenv(err, name));
    exit(EXIT_FAILURE);
}

the above code example is available pre‐packaged as the explain_unsetenv_or_die(3) function. 🫶

🎀 explain_message_unsetenv

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

explain_message_unsetenv is used to obtain an explanation of an error returned by the unsetenv(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 fr fr. 👑

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. slay. 💚
• message_size — the size in bytes of the location in which to store the returned message.
• name — the original name, exactly as passed to the unsetenv(3) system call.

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

if (unsetenv(name) < 0)
{
    char message[3000];
    explain_message_unsetenv(message, sizeof(message), name);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

the above code example is available pre‐packaged as the explain_unsetenv_or_die(3) function. 🌸

⭐ explain_message_errno_unsetenv

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

explain_message_errno_unsetenv is used to obtain an explanation of an error returned by the unsetenv(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. lowkey the most useful one in the whole squad. 💅

• 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. no cap, this trips people up constantly. 😭
• name — the original name, exactly as passed to the unsetenv(3) system call.

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

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

the above code example is available pre‐packaged as the explain_unsetenv_or_die(3) function. 🧚

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🍓 SEE ALSO 🍓

• unsetenv(3) — change or add an environment variable
• explain_unsetenv_or_die(3) — change or add an environment variable and report errors

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👑 COPYRIGHT 👑

libexplain version 1.4

Copyright (C) 2010 Peter Miller

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okay that's the whole page, bestie, you're officially fluent in explain_unsetenv(3) now 💖✨ go forth and decode your errnos, you absolute icon. this was explain_unsetenv(3), from libexplain version 1.4, copyright (C) 2010 Peter Miller — mwah, catch you in the next manpage 🦋💜🌈