explain_setenv(3)

💖 explain_setenv(3) 💖

okay bestie, so this is a page from the Library Functions Manual, and it's all about explain_setenv — the lil glow-up squad that turns your setenv(3) errors into actual explanations instead of just vibes. let's get into it 🫶

---

✨ NAME ✨

explain_setenv — explain setenv(3) errors

like, it explains them. it's giving "translator for your cryptic error codes". no cap.

---

🌸 SYNOPSIS 🌸

#include <libexplain/setenv.h>
const char *explain_setenv(const char *name, const char *value, int
overwrite);
const char *explain_errno_setenv(int errnum, const char *name, const
char *value, int overwrite);
void explain_message_setenv(char *message, int message_size, const char
*name, const char *value, int overwrite);
void explain_message_errno_setenv(char *message, int message_size, int
errnum, const char *name, const char *value, int overwrite);

four little icons, all here to serve 💅

---

🦋 DESCRIPTION 🦋

These functions may be used to obtain explanations for errors returned by the setenv(3) system call. basically: setenv(3) fails, you're standing there like 😭, and these besties hand you a whole sentence explaining why.

⭐ explain_setenv

const char *explain_setenv(const char *name, const char *value, int
overwrite);

The explain_setenv function is used to obtain an explanation of an error returned by the setenv(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. like it's not just gonna say "it broke", it's gonna tell you what broke and why, slay.

The errno global variable will be used to obtain the error value to be decoded.

• name — The original name, exactly as passed to the setenv(3) system call.
• value — The original value, exactly as passed to the setenv(3) system call.
• overwrite — The original overwrite, exactly as passed to the setenv(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. so like... don't hold onto it, it's not yours, it's communal 🫠

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library. fr fr, keep that in mind before you go parallel.

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

if (setenv(name, value, overwrite) < 0)
{
    fprintf(stderr, "%s\n", explain_setenv(name, value,
    overwrite));
    exit(EXIT_FAILURE);
}

The above code example is available pre‐packaged as the explain_setenv_or_die(3) function. iconic, honestly — they already did the work for you 💖

🎀 explain_errno_setenv

const char *explain_errno_setenv(int errnum, const char *name, const
char *value, int overwrite);

The explain_errno_setenv function is used to obtain an explanation of an error returned by the setenv(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.

• 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. so like, save your errno first, bestie, it will get stepped on 😭
• name — The original name, exactly as passed to the setenv(3) system call.
• value — The original value, exactly as passed to the setenv(3) system call.
• overwrite — The original overwrite, exactly as passed to the setenv(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 (setenv(name, value, overwrite) < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_setenv(err, name,
    value, overwrite));
    exit(EXIT_FAILURE);
}

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

💜 explain_message_setenv

void explain_message_setenv(char *message, int message_size, const char
*name, const char *value, int overwrite);

The explain_message_setenv function is used to obtain an explanation of an error returned by the setenv(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 in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe. ooooh look at you, you brought your own buffer, main character energy 👑
• 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 setenv(3) system call.
• value — The original value, exactly as passed to the setenv(3) system call.
• overwrite — The original overwrite, exactly as passed to the setenv(3) system call.

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

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

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

🍓 explain_message_errno_setenv

void explain_message_errno_setenv(char *message, int message_size, int
errnum, const char *name, const char *value, int overwrite);

The explain_message_errno_setenv function is used to obtain an explanation of an error returned by the setenv(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 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.
• name — The original name, exactly as passed to the setenv(3) system call.
• value — The original value, exactly as passed to the setenv(3) system call.
• overwrite — The original overwrite, exactly as passed to the setenv(3) system call.

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

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

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

---

👀 SEE ALSO 👀

• setenv(3) — change or add an environment variable
• explain_setenv_or_die(3) — change or add an environment variable and report errors

---

💅 COPYRIGHT 💅

libexplain version 1.4 Copyright (C) 2010 Peter Miller

---

and that's the whole page, bestie ✨ like this page is literally from the Library Functions Manual, explain_setenv(3) section, brought to you by libexplain version 1.4, copyright 2010 Peter Miller — go forth and explain your errors, you absolute icon 💖🦋🌸