explain_fgetpos(3)

💖 explain_fgetpos — bestie edition 💖

okay so like. this is explain_fgetpos(3), from the Library Functions Manual, and it's literally here to explain fgetpos(3) errors to you like a friend would, instead of leaving you staring at a raw errno like 👁️👄👁️

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✨ NAME ✨

explain_fgetpos — explain fgetpos(3) errors 🎀

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🌸 SYNOPSIS 🌸

#include <libexplain/fgetpos.h>
const char *explain_fgetpos(FILE *fp, fpos_t *pos);
const char *explain_errno_fgetpos(int errnum, FILE *fp, fpos_t *pos);
void explain_message_fgetpos(char *message, int message_size, FILE *fp,
fpos_t *pos);
void explain_message_errno_fgetpos(char *message, int message_size, int
errnum, FILE *fp, fpos_t *pos);

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🦋 DESCRIPTION 🦋

so these functions? they're the ones you call when you want an explanation for errors that fgetpos(3) returned. no cap, they will literally tell you what went wrong. 💅

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🌟 explain_fgetpos

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

the explain_fgetpos function is how you get an explanation of an error returned by the fgetpos(3) system call. the least the message will contain is the value of strerror(errno), but bestie, usually it does so much better than that and points at the actual underlying cause in more detail. it's giving detective energy 🔍

the errno global variable is the one that gets used to grab the error value that's gonna be decoded.

• fp — the original fp, exactly as passed to the fgetpos(3) system call.
• pos — the original pos, exactly as passed to the fgetpos(3) system call.

Returns:

the message explaining the error. this message buffer is shared by all libexplain functions that don't supply a buffer in their argument list. so it will be 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 many other functions in this library do too. periodt.

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

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

the above code example is available pre‐packaged as the explain_fgetpos_or_die(3) function. iconic, honestly 🫶

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🌈 explain_errno_fgetpos

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

the explain_errno_fgetpos function is used to obtain an explanation of an error returned by the fgetpos(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. sneaky of them fr fr 😤
• fp — the original fp, exactly as passed to the fgetpos(3) system call.
• pos — the original pos, exactly as passed to the fgetpos(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 (fgetpos(fp, pos) < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_fgetpos(err, fp, pos));
    exit(EXIT_FAILURE);
}

the above code example is available pre‐packaged as the explain_fgetpos_or_die(3) function. slay ✨

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🎀 explain_message_fgetpos

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

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

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

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

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

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⭐ explain_message_errno_fgetpos

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

the explain_message_errno_fgetpos function is used to obtain an explanation of an error returned by the fgetpos(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. (rude of them, ngl)
• fp — the original fp, exactly as passed to the fgetpos(3) system call.
• pos — the original pos, exactly as passed to the fgetpos(3) system call.

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

if (fgetpos(fp, pos) < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_fgetpos(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_fgetpos_or_die(3) function. ate and left no crumbs 🔥

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👀 SEE ALSO 👀

• fgetpos(3) — reposition a stream
• explain_fgetpos_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 🥹💖 this was explain_fgetpos(3) from the Library Functions Manual, brought to you by libexplain version 1.4 and Copyright (C) 2010 Peter Miller — go forth and explain your errors, main character 💫🌈🦋