explain_setpgrp(3)

💖 explain_setpgrp — the manual page, but make it a group chat 💖

okay bestie, so this is explain_setpgrp(3), and it lives in the Library Functions Manual. it's the glow-up of setpgrp(2) errors — like, the system call fumbled and now we need someone to explain what happened. that's literally this. 🫶

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✨ NAME ✨

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

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🌸 SYNOPSIS 🌸

#include <libexplain/setpgrp.h>
const char *explain_setpgrp(pid_t pid, pid_t pgid);
const char *explain_errno_setpgrp(int errnum, pid_t pid, pid_t pgid);
void explain_message_setpgrp(char *message, int message_size, pid_t pid,
pid_t pgid);
void explain_message_errno_setpgrp(char *message, int message_size, int
errnum, pid_t pid, pid_t pgid);

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🦋 DESCRIPTION 🦋

so these functions? they're how you get explanations for errors that come back from the setpgrp(2) system call. like a translator but for errno. iconic. ✨

Note: the setpgrp(2) function has two implementations, and no, they do not agree on anything. the System V version has no arguments. the BSD version has two arguments. for simplicity of implementation, the argument list you see here includes the pid and pgid arguments.

the System V getpgid() semantics can be obtained by calling setpgrp(0, 0) on systems with the BSD version — and that is the API for libexplain, even on systems that do not use the BSD API. we keep it consistent, periodt. 💅

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🌈 explain_setpgrp

const char *explain_setpgrp(pid_t pid, pid_t pgid);

the explain_setpgrp function is used to obtain an explanation of an error returned by the setpgrp(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. it's giving overachiever and we're obsessed. 💖

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

• pid — the original pid, exactly as passed to the setpgrp(2) system call. no edits, no filter, exactly as it was.
• pgid — the original pgid, exactly as passed to the setpgrp(2) system call. same energy, untouched.

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 like. screenshot it or lose it bestie. 😭

Note: this function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library. not a vibe, but it is the truth.

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

if (setpgrp(pid, pgid) < 0)
{
    fprintf(stderr, "%s\n", explain_setpgrp(pid, pgid));
    exit(EXIT_FAILURE);
}

the above code example is available pre-packaged as the explain_setpgrp_or_die(3) function. 🎀

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🌟 explain_errno_setpgrp

const char *explain_errno_setpgrp(int errnum, pid_t pid, pid_t pgid);

the explain_errno_setpgrp function is used to obtain an explanation of an error returned by the setpgrp(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. chef's kiss. 👑

• 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. yes, they're messy like that. 🙈
• pid — the original pid, exactly as passed to the setpgrp(2) system call.
• pgid — the original pgid, exactly as passed to the setpgrp(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 (setpgrp(pid, pgid) < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_setpgrp(err, pid,
    pgid));
    exit(EXIT_FAILURE);
}

the above code example is available pre-packaged as the explain_setpgrp_or_die(3) function. 💜

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💅 explain_message_setpgrp

void explain_message_setpgrp(char *message, int message_size, pid_t pid,
pid_t pgid);

the explain_message_setpgrp function is used to obtain an explanation of an error returned by the setpgrp(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. oh so NOW we're being responsible. main character behavior. 🌸
• message_size — the size in bytes of the location in which to store the returned message.
• pid — the original pid, exactly as passed to the setpgrp(2) system call.
• pgid — the original pgid, exactly as passed to the setpgrp(2) system call.

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

if (setpgrp(pid, pgid) < 0)
{
    char message[3000];
    explain_message_setpgrp(message, sizeof(message), pid, pgid);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

the above code example is available pre-packaged as the explain_setpgrp_or_die(3) function. 🦋

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🍓 explain_message_errno_setpgrp

void explain_message_errno_setpgrp(char *message, int message_size, int
errnum, pid_t pid, pid_t pgid);

the explain_message_errno_setpgrp function is used to obtain an explanation of an error returned by the setpgrp(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 deluxe combo version, lowkey. 🔥

• 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. (they will. they always do. 💀)
• pid — the original pid, exactly as passed to the setpgrp(2) system call.
• pgid — the original pgid, exactly as passed to the setpgrp(2) system call.

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

if (setpgrp(pid, pgid) < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_setpgrp(message, sizeof(message), err,
    pid, pgid);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

the above code example is available pre-packaged as the explain_setpgrp_or_die(3) function. 🧚

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👀 SEE ALSO 👀

• setpgrp(2) — set process group
• explain_setpgrp_or_die(3) — set process group 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, no cap 💖✨ — this was explain_setpgrp(3) from the Library Functions Manual, brought to you by libexplain version 1.4, copyright (C) 2011 Peter Miller. go explain some errors, you ate. 💅🎀