explain_shmat(3)

💖 explain_shmat(3) 💖

okay bestie, so you know shmat(2)? the whole shared-memory-attach thing? yeah, this is the libexplain page for it, and it's literally just here to turn its cryptic little errors into sentences you can actually read. it lives in section 3, the Library Functions Manual, if you were wondering. 🦋

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✨ NAME ✨

explain_shmat — bestie, it explains shmat(2) errors. that's the whole job. 💅

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🌸 SYNOPSIS 🌸

#include <libexplain/shmat.h>
const char *explain_shmat(int shmid, const void *shmaddr, int shmflg);
const char *explain_errno_shmat(int errnum, int shmid, const void *shmaddr, int shmflg);
void explain_message_shmat(char *message, int message_size, int shmid, const void *shmaddr, int shmflg);
void explain_message_errno_shmat(char *message, int message_size, int errnum, int shmid, const void *shmaddr, int shmflg);

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🎀 DESCRIPTION 🎀

so like, these functions are your little translators, okay? you use them to get explanations for errors that the shmat(2) system call throws back at you. no cap. 🔥

💜 explain_shmat

const char *explain_shmat(int shmid, const void *shmaddr, int shmflg);

the explain_shmat function gets you an explanation of an error returned by the shmat(2) system call. the least the message will contain is the value of strerror(errno), but usually it does so much better and points at the actual underlying cause in more detail. it's giving detective energy ngl. 🔍

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

• shmid — the original shmid, exactly as passed to the shmat(2) system call. like, untouched, periodt.
• shmaddr — the original shmaddr, exactly as passed to the shmat(2) system call.
• shmflg — the original shmflg, exactly as passed to the shmat(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 sharing that buffer will overwrite it, other threads included. 😭

Note: this function is not thread safe, because it shares a return buffer across all threads, and so do many other functions in this library. she's a sharer, it's a whole thing. 💀

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

void *result = shmat(shmid, shmaddr, shmflg);
if (!result)
{
    fprintf(stderr, "%s\n", explain_shmat(shmid, shmaddr, shmflg));
    exit(EXIT_FAILURE);
}

and guess what — that code example above is available pre-packaged as the explain_shmat_or_die(3) function. iconic behaviour, honestly. 👑

🌈 explain_errno_shmat

const char *explain_errno_shmat(int errnum, int shmid, const void *shmaddr, int shmflg);

the explain_errno_shmat function is used to obtain an explanation of an error returned by the shmat(2) system call. the least the message will contain is the value of strerror(errno), but usually it does way better and indicates the underlying cause in more detail. 🫶

• errnum — the error value to be decoded, usually grabbed from the errno global variable right before this function is called. you need this if you have to run any code between the system call being explained and this function, because lots of libc functions will go and alter the value of errno behind your back. rude, but that's the vibe. 🙈
• shmid — the original shmid, exactly as passed to the shmat(2) system call.
• shmaddr — the original shmaddr, exactly as passed to the shmat(2) system call.
• shmflg — the original shmflg, exactly as passed to the shmat(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'll get overwritten by the next call to any libexplain function that shares it, including 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.

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

void *result = shmat(shmid, shmaddr, shmflg);
if (!result)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_shmat(err, shmid, shmaddr, shmflg));
    exit(EXIT_FAILURE);
}

and yeah, that example above is available pre-packaged as the explain_shmat_or_die(3) function. ✨

🦋 explain_message_shmat

void explain_message_shmat(char *message, int message_size, int shmid, const void *shmaddr, int shmflg);

the explain_message_shmat function is used to obtain an explanation of an error returned by the shmat(2) 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. 💖

the errno global variable is 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. slay. 🎀
• message_size — the size in bytes of the location in which to store the returned message.
• shmid — the original shmid, exactly as passed to the shmat(2) system call.
• shmaddr — the original shmaddr, exactly as passed to the shmat(2) system call.
• shmflg — the original shmflg, exactly as passed to the shmat(2) system call.

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

void *result = shmat(shmid, shmaddr, shmflg);
if (!result)
{
    char message[3000];
    explain_message_shmat(message, sizeof(message), shmid, shmaddr, shmflg);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

the above code example is available pre-packaged as the explain_shmat_or_die(3) function. 💅

🌸 explain_message_errno_shmat

void explain_message_errno_shmat(char *message, int message_size, int errnum, int shmid, const void *shmaddr, int shmflg);

the explain_message_errno_shmat function is used to obtain an explanation of an error returned by the shmat(2) 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. main character explanation energy, fr fr. 🌟

• 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. 👀
• shmid — the original shmid, exactly as passed to the shmat(2) system call.
• shmaddr — the original shmaddr, exactly as passed to the shmat(2) system call.
• shmflg — the original shmflg, exactly as passed to the shmat(2) system call.

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

void *result = shmat(shmid, shmaddr, shmflg);
if (!result)
{
    int err = errno;
    char message[3000];
    explain_message_errno_shmat(message, sizeof(message), err, shmid, shmaddr, shmflg);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

the above code example is available pre-packaged as the explain_shmat_or_die(3) function. 🫶

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👑 SEE ALSO 👑

• shmat(2) — shared memory attach. the original queen. the one we're all explaining. 💜
• explain_shmat_or_die(3) — shared memory attach and report errors. the pre-packaged version, iykyk. 🔥

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💖 COPYRIGHT 💖

• libexplain version 1.4
• Copyright (C) 2011 Peter Miller

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and that's the whole page bestie, you ate it up 💅✨ this was explain_shmat(3) from the Library Functions Manual — libexplain version 1.4, Copyright (C) 2011 Peter Miller — mwah, go attach some shared memory responsibly, ily 🎀🦋💖