explain_signalfd(3)

💖 explain_signalfd — NAME 💖

okay bestie, so this is explain_signalfd and its whole job is to explain signalfd(2) errors. it's from the Library Functions Manual and it's literally the glow-up your error messages deserve. ✨

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✨ SYNOPSIS ✨

#include <libexplain/signalfd.h>
const char *explain_signalfd(int fildes, const sigset_t *mask, int flags);
const char *explain_errno_signalfd(int errnum, int fildes, const sigset_t *mask, int flags);
void explain_message_signalfd(char *message, int message_size, int fildes, const sigset_t *mask, int flags);
void explain_message_errno_signalfd(char *message, int message_size, int errnum, int fildes, const sigset_t *mask, int flags);

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🌸 DESCRIPTION 🌸

these functions are your little helpers for getting explanations of the errors that the signalfd(2) system call hands back. like, the system call said no and you wanna know why — these girls will tell you. 💅

🎀 explain_signalfd

const char *explain_signalfd(int fildes, const sigset_t *mask, int flags);

so explain_signalfd is the function you call to get an explanation of an error returned by the signalfd(2) system call. the absolute least you're gonna get is the value of strerror(errno), but usually it does much better than that and tells you the underlying cause in way more detail. it's giving detective energy fr fr 🔍

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

• fildes — the original fildes, exactly as passed to the signalfd(2) system call. no edits, no remixes, just as it was. 💖
• mask — the original mask, exactly as passed to the signalfd(2) system call.
• flags — the original flags, exactly as passed to the signalfd(2) system call.

Returns:

the message explaining the error. 👑 heads up though — this message buffer is shared by all libexplain functions that don't supply a buffer in their argument list. so the next call to any libexplain function that shares this buffer will overwrite it, and that includes calls happening in other threads. it's one communal mug and everybody's drinking from it 😭

Note: this function is not thread safe, because it shares a return buffer across all threads, and lots of other functions in this library do the same thing. plan accordingly bestie.

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

int result = signalfd(fildes, mask, flags);
if (result < 0)
{
    fprintf(stderr, "%s\n", explain_signalfd(fildes, mask, flags));
    exit(EXIT_FAILURE);
}

and the above code example is available pre-packaged as the explain_signalfd_or_die(3) function. slay, no need to write it yourself 🫶

🎀 explain_errno_signalfd

const char *explain_errno_signalfd(int errnum, int fildes, const sigset_t *mask, int flags);

explain_errno_signalfd does the same gig — it gets you an explanation of an error returned by the signalfd(2) system call. again, 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 to be decoded, usually grabbed from the errno global variable right before this function gets called. this matters if you need to run any code between the system call you're explaining and this function, because a lot of libc functions will alter the value of errno. catch it early or it's gone, iykyk 💀
• fildes — the original fildes, exactly as passed to the signalfd(2) system call.
• mask — the original mask, exactly as passed to the signalfd(2) system call.
• flags — the original flags, exactly as passed to the signalfd(2) system call.

Returns:

the message explaining the error. same deal as before — this message buffer is shared by all libexplain functions that don't supply a buffer in their argument list, and it gets 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, and many other functions in this library are the same way.

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

int result = signalfd(fildes, mask, flags);
if (result < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_signalfd(err, fildes, mask, flags));
    exit(EXIT_FAILURE);
}

and yep, the above code example is pre-packaged as the explain_signalfd_or_die(3) function. 💅

🎀 explain_message_signalfd

void explain_message_signalfd(char *message, int message_size, int fildes, const sigset_t *mask, int flags);

explain_message_signalfd gets you an explanation of an error returned by the signalfd(2) system call. least you'll see is strerror(errno), but usually it's way more helpful and nails 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. if you supply a suitable message return buffer, this function is thread safe. your own buffer, your own rules, main character energy 👑
• message_size — the size in bytes of the location where the returned message gets stored.
• fildes — the original fildes, exactly as passed to the signalfd(2) system call.
• mask — the original mask, exactly as passed to the signalfd(2) system call.
• flags — the original flags, exactly as passed to the signalfd(2) system call.

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

int result = signalfd(fildes, mask, flags);
if (result < 0)
{
    char message[3000];
    explain_message_signalfd(message, sizeof(message), fildes, mask, flags);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

and the above code example is pre-packaged as the explain_signalfd_or_die(3) function. iconic. 🎀

🎀 explain_message_errno_signalfd

void explain_message_errno_signalfd(char *message, int message_size, int errnum, int fildes, const sigset_t *mask, int flags);

explain_message_errno_signalfd gets you an explanation of an error returned by the signalfd(2) system call. minimum effort is strerror(errno), but usually it delivers so much more and points at the underlying cause in detail. 🔥

• message — the location where the returned message gets stored. if a suitable message return buffer is supplied, this function is thread safe. yes bestie, you CAN have nice things 🫶
• 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. 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. save it while it's fresh 😭
• fildes — the original fildes, exactly as passed to the signalfd(2) system call.
• mask — the original mask, exactly as passed to the signalfd(2) system call.
• flags — the original flags, exactly as passed to the signalfd(2) system call.

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

int result = signalfd(fildes, mask, flags);
if (result < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_signalfd(message, sizeof(message), err, fildes, mask, flags);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

and the above code example is pre-packaged as the explain_signalfd_or_die(3) function. periodt. 💅

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👀 SEE ALSO 👀

• signalfd(2) — create a file descriptor for accepting signals
• explain_signalfd_or_die(3) — create a file descriptor for accepting signals and report errors

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📜 COPYRIGHT 📜

• libexplain version 1.4
• Copyright (C) 2009 Peter Miller

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and that's the whole page bestie!! 🦋 go forth and let your signalfd(2) errors be beautifully explained, you've got this 💖✨🌸 — this was explain_signalfd(3) from the Library Functions Manual, running on libexplain version 1.4, with Copyright (C) 2009 Peter Miller. mwah, bye!! 🎀💜