explain_setlinebuf(3)

💖 explain_setlinebuf — the manual page, but make it make sense 💖

ok so bestie, this is a page from the Library Functions Manual, and it's all about one very specific little glow-up: turning those cryptic setlinebuf(3) errors into actual sentences that tell you what went wrong. we're talking explain_setlinebuf(3) energy. let's get into it ✨

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🌸 NAME 🌸

explain_setlinebuf — explain setlinebuf(3) errors

like, it literally explains them. that's the whole job. it's giving translator-for-your-error-codes 🫶

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🎀 SYNOPSIS 🎀

#include <libexplain/setlinebuf.h>
const char *explain_setlinebuf(FILE *fp);
const char *explain_errno_setlinebuf(int errnum, FILE *fp);
void explain_message_setlinebuf(char *message, int message_size, FILE *fp);
void explain_message_errno_setlinebuf(char *message, int message_size, int errnum, FILE *fp);

four little functions, all here to hold your hand 💅

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✨ DESCRIPTION ✨

so these functions? they're your little helpers for getting explanations of errors that come back from the setlinebuf(3) system call. that's it, that's the vibe. 🌈

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💜 explain_setlinebuf

const char *explain_setlinebuf(FILE *fp);

explain_setlinebuf is the function you call to get an explanation of an error returned by the setlinebuf(3) system call. the least you'll get in that message is the value of strerror(errno), but bestie, usually it does so much better and tells you the actual underlying cause in more detail. no cap. 🔥

the errno global variable is what gets used to grab the error value that needs decoding.

• fp — the original fp, exactly as it was passed to the setlinebuf(3) system call. don't get cute with it, pass it as-is.

Returns:

the message explaining the error. heads up though: this message buffer is shared by every libexplain function that doesn't take a buffer in its argument list. so it will get 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 honestly, so do many other functions in this library. it's giving communal-notebook energy.

Example: this function is meant to be used in a fashion similar to this little guy:

errno = 0;
void result = setlinebuf(fp);
if (result < 0 && errno != 0)
{
    fprintf(stderr, "%s\n", explain_setlinebuf(fp));
    exit(EXIT_FAILURE);
}

and the above code example is available pre-packaged as the explain_setlinebuf_or_die(3) function. iconic of them honestly 🎀

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💜 explain_errno_setlinebuf

const char *explain_errno_setlinebuf(int errnum, FILE *fp);

explain_errno_setlinebuf does the same thing — obtain an explanation of an error returned by the setlinebuf(3) system call. the least the message will contain is the value of strerror(errno), but usually it goes way harder and points at the underlying cause in more detail. ✨

• errnum — the error value that needs decoding, usually grabbed from the errno global variable just before this function is called. this matters if you need to run any code between the system call being explained and this function, because so many libc functions will mess with the value of errno. sneak attack fr fr. 🙈
• fp — the original fp, exactly as passed to the setlinebuf(3) system call.

Returns:

the message explaining the error. same situation as before: this message buffer is shared by all libexplain functions that don't supply a buffer in their argument list, and it will be overwritten by the next call to any libexplain function sharing that buffer, other threads included. 😭

Note: not thread safe — shared return buffer across all threads, plus lots of other functions in this library. same deal.

Example: intended to be used in a fashion similar to:

errno = 0;
void result = setlinebuf(fp);
if (result < 0 && errno != 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_setlinebuf(err, fp));
    exit(EXIT_FAILURE);
}

and yeah, this code example is available pre-packaged as the explain_setlinebuf_or_die(3) function. 💖

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💜 explain_message_setlinebuf

void explain_message_setlinebuf(char *message, int message_size, FILE *fp);

explain_message_setlinebuf gets you an explanation of an error returned by the setlinebuf(3) system call. least it'll contain is the value of strerror(errno), but usually it does much better and reveals the underlying cause in more detail. 🌸

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

• message — the location where the returned message gets stored. and good news bestie: if you supply a suitable message return buffer, this function is thread safe. 👑
• message_size — the size in bytes of the location where the returned message gets stored.
• fp — the original fp, exactly as passed to the setlinebuf(3) system call.

Example: intended to be used in a fashion similar to:

errno = 0;
void result = setlinebuf(fp);
if (result < 0 && errno != 0)
{
    char message[3000];
    explain_message_setlinebuf(message, sizeof(message), fp);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

and once again, that code example is available pre-packaged as the explain_setlinebuf_or_die(3) function. 🦋

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💜 explain_message_errno_setlinebuf

void explain_message_errno_setlinebuf(char *message, int message_size, int errnum, FILE *fp);

explain_message_errno_setlinebuf obtains an explanation of an error returned by the setlinebuf(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. periodt. 💅

• message — the location where the returned message gets stored. if a suitable message return buffer is supplied, this function is thread safe. 🫶
• message_size — the size in bytes of the location where the returned message gets stored.
• errnum — the error value to be decoded, usually obtained from the errno global variable just before this function is called. necessary if you need to call any code between the system call being explained and this function, because many libc functions will alter the value of errno.
• fp — the original fp, exactly as passed to the setlinebuf(3) system call.

Example: intended to be used in a fashion similar to:

errno = 0;
void result = setlinebuf(fp);
if (result < 0 && errno != 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_setlinebuf(message, sizeof(message),
    err, fp);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

and yes bestie, the above code example is available pre-packaged as the explain_setlinebuf_or_die(3) function. ⭐

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👀 SEE ALSO 👀

• setlinebuf(3) — stream buffering operations
• explain_setlinebuf_or_die(3) — stream buffering operations and report errors

go read those too, they're the whole supporting cast 💜

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📜 COPYRIGHT 📜

• libexplain version 1.4
• Copyright (C) 2010 Peter Miller

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ok that's the whole page, you ate that, go forth and debug with confidence bestie 💖✨🌸 this was explain_setlinebuf(3) from the Library Functions Manual, brought to you by libexplain version 1.4, copyright (C) 2010 Peter Miller — mwah, no notes, see u in the next manpage 🎀🦋👑