explain_shmctl(3)

✨ NAME ✨

explain_shmctl — explain shmctl(2) errors 🫶

Okay so welcome to the manual page for explain_shmctl(3) from the Library Functions Manual. Bestie, if your shared-memory syscall is throwing a fit and you're just standing there like "why 😭", this whole family of functions is literally here to tell you what went down. No cap.

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🎀 SYNOPSIS 🎀

#include <libexplain/shmctl.h>
const char *explain_shmctl(int shmid, int command, struct shmid_ds
*data);
const char *explain_errno_shmctl(int errnum, int shmid, int command,
struct shmid_ds *data);
void explain_message_shmctl(char *message, int message_size, int shmid,
int command, struct shmid_ds *data);
void explain_message_errno_shmctl(char *message, int message_size, int
errnum, int shmid, int command, struct shmid_ds *data);

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💅 DESCRIPTION 💅

These functions may be used to obtain explanations for errors returned by the shmctl(2) system call. That's the whole vibe. periodt ✨

🦋 explain_shmctl

const char *explain_shmctl(int shmid, int command, struct shmid_ds
*data);

The explain_shmctl function is used to obtain an explanation of an error returned by the shmctl(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. Like, it's giving actual detective work 🔍.

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

• shmid — the original shmid, exactly as passed to the shmctl(2) system call.
• command — the original command, exactly as passed to the shmctl(2) system call.
• data — the original data, exactly as passed to the shmctl(2) 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. So do not get attached to it, bestie, it moves on fast 💀

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library. Fr fr, be careful with that one.

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

if (shmctl(shmid, command, data) < 0)
{
    fprintf(stderr, "%s\n", explain_shmctl(shmid, command,
    data));
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_shmctl_or_die(3) function. Convenient queen behaviour ✨

🌸 explain_errno_shmctl

const char *explain_errno_shmctl(int errnum, int shmid, int command,
struct shmid_ds *data);

The explain_errno_shmctl function is used to obtain an explanation of an error returned by the shmctl(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.

• 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. iykyk — libc will snatch your errno right out from under you 🫠
• shmid — the original shmid, exactly as passed to the shmctl(2) system call.
• command — the original command, exactly as passed to the shmctl(2) system call.
• data — the original data, exactly as passed to the shmctl(2) 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 (shmctl(shmid, command, data) < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_shmctl(err, shmid,
    command, data));
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_shmctl_or_die(3) function.

🧚 explain_message_shmctl

void explain_message_shmctl(char *message, int message_size, int shmid,
int command, struct shmid_ds *data);

The explain_message_shmctl function is used to obtain an explanation of an error returned by the shmctl(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.

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. Ooh, she's safe AND she's serving ✨
• 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 shmctl(2) system call.
• command — the original command, exactly as passed to the shmctl(2) system call.
• data — the original data, exactly as passed to the shmctl(2) system call.

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

if (shmctl(shmid, command, data) < 0)
{
    char message[3000];
    explain_message_shmctl(message, sizeof(message), shmid,
    command, data);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_shmctl_or_die(3) function.

💜 explain_message_errno_shmctl

void explain_message_errno_shmctl(char *message, int message_size, int
errnum, int shmid, int command, struct shmid_ds *data);

The explain_message_errno_shmctl function is used to obtain an explanation of an error returned by the shmctl(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.

• 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 shmctl(2) system call.
• command — the original command, exactly as passed to the shmctl(2) system call.
• data — the original data, exactly as passed to the shmctl(2) system call.

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

if (shmctl(shmid, command, data) < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_shmctl(message, sizeof(message), err,
    shmid, command, data);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_shmctl_or_die(3) function.

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👀 SEE ALSO 👀

• shmctl(2) — shared memory control
• explain_shmctl_or_die(3) — shared memory control and report errors

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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 💖 This was explain_shmctl(3), Library Functions Manual, brought to you by libexplain version 1.4, Copyright (C) 2011 Peter Miller — iconic, no notes, go debug your shared memory like a main character 🎀🦋✨