explain_snprintf(3)

💅 explain_snprintf — Library Functions Manual 💅

okay bestie, sit down, because we're about to talk about the iconic little corner of libexplain that turns your sad snprintf(3) failures into actual sentences. yes, the manual name is literally Library Functions Manual and yes, this whole page is about making errors make sense. slay.

✨ NAME ✨

explain_snprintf — explain snprintf(3) errors. that's it, that's the whole job, and it does it beautifully.

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🦋 SYNOPSIS 🦋

#include <libexplain/snprintf.h>
const char *explain_snprintf(char *data, size_t data_size, const char
*format);
const char *explain_errno_snprintf(int errnum, char *data, size_t
data_size, const char *format);
void explain_message_snprintf(char *message, int message_size, char
*data, size_t data_size, const char *format);
void explain_message_errno_snprintf(char *message, int message_size, int
errnum, char *data, size_t data_size, const char *format);

look at those four besties, each one a different flavor of "let me tell you what went wrong." 💖

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🌸 DESCRIPTION 🌸

so here's the vibe: these functions are how you get explanations for errors returned by the snprintf(3) system call. like, actual explanations, not just a cryptic number. main character energy, honestly.

🎀 explain_snprintf

const char *explain_snprintf(char *data, size_t data_size, const char
*format);

the explain_snprintf function is here to hand you an explanation of an error returned by the snprintf(3) system call. the least the message will contain is the value of strerror(errno), but usually it will do much better and point at the underlying cause in more detail. it's giving overachiever, and we love that for it.

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

• data — the original data, exactly as passed to the snprintf(3) system call.
• data_size — the original data_size, exactly as passed to the snprintf(3) system call.
• format — the original format, exactly as passed to the snprintf(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. it will be overwritten by the next call to any libexplain function which shares this buffer, including other threads. so like… don't get attached. 🙈

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

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

errno = 0;
int result = snprintf(data, data_size, format);
if (result < 0 && errno != 0)
{
    fprintf(stderr, "%s\n", explain_snprintf(data, data_size,
    format));
    exit(EXIT_FAILURE);
}

the above code example is available pre‐packaged as the explain_snprintf_or_die(3) function. iconic of it, honestly.

💜 explain_errno_snprintf

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

the explain_errno_snprintf function is used to obtain an explanation of an error returned by the snprintf(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. yes bestie, errno is fickle like that. 😭
• data — the original data, exactly as passed to the snprintf(3) system call.
• data_size — the original data_size, exactly as passed to the snprintf(3) system call.
• format — the original format, exactly as passed to the snprintf(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:

errno = 0;
int result = snprintf(data, data_size, format);
if (result < 0 && errno != 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_snprintf(err, data,
    data_size, format));
    exit(EXIT_FAILURE);
}

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

🌈 explain_message_snprintf

void explain_message_snprintf(char *message, int message_size, char
*data, size_t data_size, const char *format);

the explain_message_snprintf function is used to obtain an explanation of an error returned by the snprintf(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. look at her, being all responsible and grown up. 👑
• 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 snprintf(3) system call.
• data_size — the original data_size, exactly as passed to the snprintf(3) system call.
• format — the original format, exactly as passed to the snprintf(3) system call.

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

errno = 0;
int result = snprintf(data, data_size, format);
if (result < 0 && errno != 0)
{
    char message[3000];
    explain_message_snprintf(message, sizeof(message), data,
    data_size, format);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

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

🫶 explain_message_errno_snprintf

void explain_message_errno_snprintf(char *message, int message_size, int
errnum, char *data, size_t data_size, const char *format);

the explain_message_errno_snprintf function is used to obtain an explanation of an error returned by the snprintf(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.
• data — the original data, exactly as passed to the snprintf(3) system call.
• data_size — the original data_size, exactly as passed to the snprintf(3) system call.
• format — the original format, exactly as passed to the snprintf(3) system call.

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

errno = 0;
int result = snprintf(data, data_size, format);
if (result < 0 && errno != 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_snprintf(message, sizeof(message), err,
    data, data_size, format);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

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

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⭐ SEE ALSO ⭐

• snprintf(3) — formatted output conversion
• explain_snprintf_or_die(3) — formatted output conversion and report errors

go read those too, bestie. iykyk. 🦋

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💖 COPYRIGHT 💖

libexplain version 1.4 Copyright (C) 2010 Peter Miller

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and that's the whole page, gorgeous. this was explain_snprintf(3) from the Library Functions Manual, brought to you by libexplain version 1.4, copyright (C) 2010 Peter Miller. no cap, you understood all of that. now go forth and explain your errors. ✨👑💅