explain_getresgid(3)

✨ explain_getresgid(3) ✨

okay so bestie, buckle up 💖 this is a page from the Library Functions Manual, and it's all about explain_getresgid — the libexplain glow-up that turns your getresgid(2) errors into actual explanations instead of cryptic nothing-burgers.

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🌸 NAME 🌸

explain_getresgid — it explains getresgid(2) errors, that's the whole vibe 🫶

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✨ SYNOPSIS ✨

#include <libexplain/getresgid.h>
const char *explain_getresgid(gid_t *rgid, gid_t *egid, gid_t *sgid);
const char *explain_errno_getresgid(int errnum, gid_t *rgid, gid_t *egid, gid_t *sgid);
void explain_message_getresgid(char *message, int message_size, gid_t *rgid, gid_t *egid, gid_t *sgid);
void explain_message_errno_getresgid(char *message, int message_size, int errnum, gid_t *rgid, gid_t *egid, gid_t *sgid);

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💅 DESCRIPTION 💅

So these functions? They're how you get explanations for errors that the getresgid(2) system call hands back. Like, the system call said no, and libexplain says why 💁‍♀️

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🎀 explain_getresgid

const char *explain_getresgid(gid_t *rgid, gid_t *egid, gid_t *sgid);

The explain_getresgid function grabs you an explanation of an error returned by the getresgid(2) system call. The least the message will contain is the value of strerror(errno), but usually it does so much better and tells you the underlying cause in way more detail. it's giving detective energy 🔍

The errno global variable is the one that gets used to obtain the error value to be decoded.

• rgid — the original rgid, exactly as passed to the getresgid(2) system call. no edits, no glow-up, the exact same one.
• egid — the original egid, exactly as passed to the getresgid(2) system call.
• sgid — the original sgid, exactly as passed to the getresgid(2) system call.

Returns:

The message explaining the error. Heads up though — this message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. So it will get overwritten by the next call to any libexplain function that shares this buffer, including other threads. 😭 it's not yours, it's everyone's.

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. periodt.

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

if (getresgid(rgid, egid, sgid) < 0)
{
    fprintf(stderr, "%s\n", explain_getresgid(rgid, egid, sgid));
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_getresgid_or_die(3) function. yes, it's already done for you, you're welcome 🫶

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🦋 explain_errno_getresgid

const char *explain_errno_getresgid(int errnum, gid_t *rgid, gid_t *egid, gid_t *sgid);

The explain_errno_getresgid function is used to obtain an explanation of an error returned by the getresgid(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. iconic behaviour tbh ✨

• errnum — the error value to be decoded, usually obtained from the errno global variable just before this function is called. You need this if you have to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno. so grab it early, bestie, it moves fast 💀
• rgid — the original rgid, exactly as passed to the getresgid(2) system call.
• egid — the original egid, exactly as passed to the getresgid(2) system call.
• sgid — the original sgid, exactly as passed to the getresgid(2) system call.

Returns:

The message explaining the error. Same tea as before: this message buffer is shared by all libexplain functions which do not supply a buffer in their argument list, and it 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 do the same.

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

if (getresgid(rgid, egid, sgid) < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_getresgid(err, rgid,
    egid, sgid));
    exit(EXIT_FAILURE);
}

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

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💜 explain_message_getresgid

void explain_message_getresgid(char *message, int message_size, gid_t *rgid, gid_t *egid, gid_t *sgid);

The explain_message_getresgid function is used to obtain an explanation of an error returned by the getresgid(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 🎉 look at that.
• message_size — the size in bytes of the location in which to store the returned message.
• rgid — the original rgid, exactly as passed to the getresgid(2) system call.
• egid — the original egid, exactly as passed to the getresgid(2) system call.
• sgid — the original sgid, exactly as passed to the getresgid(2) system call.

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

if (getresgid(rgid, egid, sgid) < 0)
{
    char message[3000];
    explain_message_getresgid(message, sizeof(message), rgid,
    egid, sgid);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

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

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🌈 explain_message_errno_getresgid

void explain_message_errno_getresgid(char *message, int message_size, int errnum, gid_t *rgid, gid_t *egid, gid_t *sgid);

The explain_message_errno_getresgid function is used to obtain an explanation of an error returned by the getresgid(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 👑

• 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. (iykyk 😭)
• rgid — the original rgid, exactly as passed to the getresgid(2) system call.
• egid — the original egid, exactly as passed to the getresgid(2) system call.
• sgid — the original sgid, exactly as passed to the getresgid(2) system call.

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

if (getresgid(rgid, egid, sgid) < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_getresgid(message, sizeof(message),
    err, rgid, egid, sgid);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

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

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👀 SEE ALSO 👀

• getresgid(2) — get real, effective and saved group IDs
• explain_getresgid_or_die(3) — get real, effective and saved group IDs and report errors

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📜 COPYRIGHT 📜

• libexplain version 1.4
• Copyright (C) 2012 Peter Miller

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okay that's the whole page bestie, you ate that 💅✨ and for the cute sign-off: this whole thing is explain_getresgid(3) from the Library Functions Manual, brought to you by libexplain version 1.4, with Copyright (C) 2012 Peter Miller — so go forth and decode your errnos, you absolute icon 🎀🦋💖