explain_fsetpos(3)

✨ explain_fsetpos — the libexplain glow-up for fsetpos(3) errors ✨

okay so bestie, welcome to the Library Functions Manual entry for explain_fsetpos(3) 💖 if fsetpos(3) ever left you on read with a cryptic error, this whole little family of functions is here to translate the drama into actual words you can read. no cap.

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🌸 NAME 🌸

explain_fsetpos — explain fsetpos(3) errors 💅

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🎀 SYNOPSIS 🎀

#include <libexplain/fsetpos.h>
const char *explain_fsetpos(FILE *fp, fpos_t *pos);
const char *explain_errno_fsetpos(int errnum, FILE *fp, fpos_t *pos);
void explain_message_fsetpos(char *message, int message_size, FILE *fp,
fpos_t *pos);
void explain_message_errno_fsetpos(char *message, int message_size, int
errnum, FILE *fp, fpos_t *pos);

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🦋 DESCRIPTION 🦋

so these functions are literally your translator besties 🫶 you use them to get actual explanations for errors that come back from the fsetpos(3) system call. no more squinting at a bare number like "what does that even mean". they said we'll tell you. and they do.

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💜 explain_fsetpos

const char *explain_fsetpos(FILE *fp, fpos_t *pos);

the explain_fsetpos function is the one you call when you want an explanation of an error returned by the fsetpos(3) system call. the least the message will contain is the value of strerror(errno), but usually it does way better than the bare minimum — it'll indicate the underlying cause in more detail. it's giving overachiever and we're obsessed. 👑

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

• fp — the original fp, exactly as passed to the fsetpos(3) system call. yes, exactly. don't be out here editing it. 🙈
• pos — the original pos, exactly as passed to the fsetpos(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... screenshot it before someone else edits the group chat. 😭

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:

if (fsetpos(fp, pos) < 0)
{
    fprintf(stderr, "%s\n", explain_fsetpos(fp, pos));
    exit(EXIT_FAILURE);
}

the above code example is available pre‐packaged as the explain_fsetpos_or_die(3) function. iconic behaviour tbh. ✨

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💖 explain_errno_fsetpos

const char *explain_errno_fsetpos(int errnum, FILE *fp, fpos_t *pos);

the explain_errno_fsetpos function is used to obtain an explanation of an error returned by the fsetpos(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, grab errno fast, bestie, it does not wait for you. 🏃‍♀️
• fp — the original fp, exactly as passed to the fsetpos(3) system call.
• pos — the original pos, exactly as passed to the fsetpos(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. (yes again. the buffer is a shared snack. everybody's eating. 🍓)

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

if (fsetpos(fp, pos) < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_fsetpos(err, fp, pos));
    exit(EXIT_FAILURE);
}

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

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🌈 explain_message_fsetpos

void explain_message_fsetpos(char *message, int message_size, FILE *fp,
fpos_t *pos);

the explain_message_fsetpos function is used to obtain an explanation of an error returned by the fsetpos(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 go!! main character energy. 👑
• message_size — the size in bytes of the location in which to store the returned message.
• fp — the original fp, exactly as passed to the fsetpos(3) system call.
• pos — the original pos, exactly as passed to the fsetpos(3) system call.

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

if (fsetpos(fp, pos) < 0)
{
    char message[3000];
    explain_message_fsetpos(message, sizeof(message), fp, pos);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

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

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🧚 explain_message_errno_fsetpos

void explain_message_errno_fsetpos(char *message, int message_size, int
errnum, FILE *fp, fpos_t *pos);

the explain_message_errno_fsetpos function is used to obtain an explanation of an error returned by the fsetpos(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. slay.
• 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.
• fp — the original fp, exactly as passed to the fsetpos(3) system call.
• pos — the original pos, exactly as passed to the fsetpos(3) system call.

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

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

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

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👀 SEE ALSO 👀

• fsetpos(3) — reposition a stream
• explain_fsetpos_or_die(3) — reposition a stream 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!! 💖 ty for reading, go forth and fsetpos(3) responsibly, and remember: the shared buffer does not care about your feelings, so copy that message while you can. mwah. 🎀✨ (source and version dropped right there in the copyright, and yeah, Copyright (C) 2010 Peter Miller — respect the icon 💅)