explain_putenv(3)

✨ explain_putenv ✨

okay so bestie, you know putenv(3)? the little syscall that changes or adds an environment variable? sometimes it goes 💀 and returns an error, and this whole page — from the Library Functions Manual family — is here to explain how you get a pretty explanation of that error instead of just staring at errno. it's giving "let me translate the error for you, bestie." no cap. 💅

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🎀 NAME 🎀

explain_putenv — explain putenv(3) errors

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🌸 SYNOPSIS 🌸

#include <libexplain/putenv.h>
const char *explain_putenv(char *string);
const char *explain_errno_putenv(int errnum, char *string);
void explain_message_putenv(char *message, int message_size, char
*string);
void explain_message_errno_putenv(char *message, int message_size, int
errnum, char *string);

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🦋 DESCRIPTION 🦋

so these functions? they're your little helpers for getting explanations of errors returned by the putenv(3) system call. that's the whole vibe. periodt. ✨

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💖 explain_putenv 💖

const char *explain_putenv(char *string);

the explain_putenv function is what you call to obtain an explanation of an error returned by the putenv(3) system call. the least the message will contain 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 main character energy for your error messages, honestly. 🔥

the errno global variable is the one used to obtain the error value to be decoded.

• string — the original string, exactly as passed to the putenv(3) system call. like, character for character, no edits bestie.

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. it 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. ngl, keep that in mind.

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

if (putenv(string) < 0)
{
    fprintf(stderr, "%s\n", explain_putenv(string));
    exit(EXIT_FAILURE);
}

the above code example is available pre-packaged as the explain_putenv_or_die(3) function. slay, they already did the work for you. 🫶

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🌈 explain_errno_putenv 🌈

const char *explain_errno_putenv(int errnum, char *string);

the explain_errno_putenv function is used to obtain an explanation of an error returned by the putenv(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. ✨

• errnum — the error value to be decoded, usually grabbed 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 it first, bestie.
• string — the original string, exactly as passed to the putenv(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 (putenv(string) < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_putenv(err, string));
    exit(EXIT_FAILURE);
}

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

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🧚 explain_message_putenv 🧚

void explain_message_putenv(char *message, int message_size, char
*string);

the explain_message_putenv function is used to obtain an explanation of an error returned by the putenv(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. 🎀
• message_size — the size in bytes of the location in which to store the returned message.
• string — the original string, exactly as passed to the putenv(3) system call.

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

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

the above code example is available pre-packaged as the explain_putenv_or_die(3) function. ⭐

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👑 explain_message_errno_putenv 👑

void explain_message_errno_putenv(char *message, int message_size, int
errnum, char *string);

the explain_message_errno_putenv function is used to obtain an explanation of an error returned by the putenv(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. (yes we said it before, it's still true, it's that important 💜)
• string — the original string, exactly as passed to the putenv(3) system call.

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

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

the above code example is available pre-packaged as the explain_putenv_or_die(3) function. ate. 🍓

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💜 SEE ALSO 💜

• putenv(3) — change or add an environment variable
• explain_putenv_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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and that's the whole page, bestie — explain_putenv(3), straight from the Library Functions Manual, libexplain version 1.4, © 2010 Peter Miller. go forth and have immaculate error messages. 💖✨🦋