PTHREAD...PSHARED(3POSIX)

💅 PTHREAD...PSHARED — the POSIX Programmer's Manual, bestie edition 🎀

okay so this page lives in the POSIX Programmer's Manual (yes, that whole volume, she's iconic) and it's all about one tiny-but-mighty attribute on your mutex attributes object: the process-shared attribute. get it, set it, that's the whole vibe. ✨

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🌸 PROLOG 🌸

bestie, real talk first: this manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (so like, go consult the corresponding Linux manual page for the deets on Linux behavior), or — plot twist — the interface may not even be implemented on Linux at all. 🙈

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👑 NAME 👑

pthread_mutexattr_getpshared, pthread_mutexattr_setpshared — get and set the process-shared attribute. it's giving "two functions, one job". 🫶

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✨ SYNOPSIS ✨

#include <pthread.h>

int pthread_mutexattr_getpshared(const pthread_mutexattr_t
    *restrict attr, int *restrict pshared);
int pthread_mutexattr_setpshared(pthread_mutexattr_t *attr,
    int pshared);

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💖 DESCRIPTION 💖

so here's the tea. ☕

The pthread_mutexattr_getpshared() function shall obtain the value of the process-shared attribute from the attributes object referenced by attr. she's the reader, she just reports back.

The pthread_mutexattr_setpshared() function shall set the process-shared attribute in an initialized attributes object referenced by attr. she's the writer, she makes it happen. 💅

now, the actual lore: the process-shared attribute is set to PTHREAD_PROCESS_SHARED to permit a mutex to be operated upon by any thread that has access to the memory where the mutex is allocated — even if that mutex is allocated in memory that is shared by multiple processes. like, multiple processes, one mutex, no cap. 🔥 for further requirements, go see Section 2.9.9, Synchronization Object Copies and Alternative Mappings. and the default value of the attribute? PTHREAD_PROCESS_PRIVATE. that's the factory setting, the starting point, the default fit. ✨

🚨 The behavior is undefined if the value specified by the attr argument to pthread_mutexattr_getpshared() or pthread_mutexattr_setpshared() does not refer to an initialized mutex attributes object. uninitialized attr = chaos, and not the cute kind. 💀

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🌈 RETURN VALUE 🌈

• upon successful completion, pthread_mutexattr_setpshared() shall return zero; otherwise, an error number shall be returned to indicate the error. periodt.
• upon successful completion, pthread_mutexattr_getpshared() shall return zero and store the value of the process-shared attribute of attr into the object referenced by the pshared parameter. otherwise, an error number shall be returned to indicate the error.

so yeah — 0 means slay, anything else means read the number and go fix something. 🧚

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🦋 ERRORS 🦋

The pthread_mutexattr_setpshared() function may fail if:

• EINVAL — the new value specified for the attribute is outside the range of legal values for that attribute. bestie you literally handed her an illegal value, what did you expect. 😭

also super important: these functions shall not return an error code of [EINTR]. not a thing here, don't go looking for it. 🙅

and fyi — the following sections are informative. so like, they're context, not commandments. 📖

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🍓 EXAMPLES 🍓

None.

she said: no examples, figure it out. iconic honestly.

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💜 APPLICATION USAGE 💜

None.

nothing here either. the void is empty and we respect her. ✨

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🎀 RATIONALE 🎀

If an implementation detects that the value specified by the attr argument to pthread_mutexattr_getpshared() or pthread_mutexattr_setpshared() does not refer to an initialized mutex attributes object, it is recommended that the function should fail and report an [EINVAL] error. like, it's not required-required, but it's the polite thing to do. 🫶

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⭐ FUTURE DIRECTIONS ⭐

None.

the future is bright and completely unspecified. main character energy. 👑

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🧚 SEE ALSO 🧚

• pthread_cond_destroy()
• pthread_create()
• pthread_mutex_destroy()
• pthread_mutexattr_destroy()

The Base Definitions volume of POSIX.1‐2017, <pthread.h>

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📜 COPYRIGHT 📜

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

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and that's the whole page, bestie 💖 this one came from IEEE/The Open Group, 2017, and it's the PTHREAD...PSHARED(3POSIX) girl herself. go forth and share your mutexes responsibly. no cap. 💅✨