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Questions tagged [posix]

POSIX is an acronym for Portable Operating System Interface, a family of standards specified by the IEEE for maintaining compatibility between operating systems.

POSIX is a family of standards that specify the behavior of Unix-like operating systems.

These standards define:

  • A standard operating system interface and environment.
  • A programming API for the C programming language.
  • The behavior of a command interpreter (or shell).
  • The behavior of common utility programs invocable from the shell.

The POSIX standards are developed by the Austin Group, sponsored by the Portable Application Standards Committee of the IEEE.

The current set of POSIX standards is available online.

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Difference between POSIX, Single UNIX Specification, and Open Group Base Specifications?

What are the differences between POSIX, the Single UNIX Specification, and the Open Group Base Specifications? I think their purpose is for determining if an OS is Unix?
Tim
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What are the POSIX "mandatory utilities"?

The POSIX docs here and here refer to "mandatory utilities", but I can't find any listing of such utilities. Is there one somewhere in the POSIX docs? Granted, the links given above point to older version of the docs. Maybe the nomenclature has…
kjo
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Is the double dash still the posix standard for long switches?

I've read several question about double dash: Single dashes - for single-character options, but double dashes -- for words? What does -- (double-dash) mean? (also known as “bare double dash”) However I remember about a teacher 4 years ago telling…
Kiwy
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Does POSIX specify whether to continue script when nested dot fails?

For example, if I have example.sh with following content . non-existing.sh echo 'continues!' Then I source the script in an interactive session with . ./example.sh, should I see “continues!” in the terminal? The standard specifies If no readable…
Franklin Yu
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Are "mostly POSIX-compliant" systems still considered POSIX systems?

Irix and OS X are POSIX systems because they are fully-POSIX-compliant. However, operating systems like FreeBSD, Haiku, and GNU/Linux, for example, are "mostly-POSIX-compliant". Can people still correctly refer to such systems as POSIX systems?
Devyn Collier Johnson
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Is POSIX prescriptive or descriptive?

Is POSIX a description of how applications have implemented each specific part of UNIX in the past or is it a prescriptive norm of how UNIX must be implemented ? If descriptive, only the features that are common to all included implementations would…
user232326
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Is it safe to close a directory stream (DIR *) in both the parent and child process?

This page describes the guaranteed behavior of the functions readdir and readdir_r and contains the following sentence: After a call to fork(), either the parent or child (but not both) may continue processing the directory stream using…
Greg Nisbet
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Is Posix a subset of Single UNIX Specification?

I know a question about the differences between Posix and SUS has already been asked and answered beautifully. Anyway, the answers seemed to suggest the possibility that SUS "encompasses more than Posix", and there are certain things in SUS that are…
Gabriele Scarlatti
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How is the time stamp number in /etc/shadow calculated?

On my system the man page of shadow defines the third column value this way: The date of the last password change, expressed as the number of days since Jan 1, 1970. I have an example value "17050". passwd -S says this is the "2016-09-06". But…
ceving
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Why not just use standard streams instead of using filenames?

While I understand that programs like mv need an actual filename as a parameter, programs like sort could just read from standard input and write to standard output like names | sort > names instead of using a filename and providing options like -o:…
seriousdev
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Why is blkcnt_t a signed value if it measures number of blocks?

In the refs related to the type blkcnt_t is defined as: blkcnt_t Used for file block counts. also it states: blkcnt_t and off_t shall be signed integer types. (see…
humanityANDpeace
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What, as examples, can produce a POLLNVAL?

The reference about poll() just says “The specified fd value is invalid. This flag is only valid in the revents member; it shall ignored in the events member.”. That's not clear (at least to me): if the file descriptor is invalid, shouldn't poll…
Hibou57
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Why is SIGIO not in the POSIX signal specification?

In the 2004 version of the 1003.1 POSIX standard by the Open Group there is no mention of SIGIO. Why is that?
Tyler Durden
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How can I test what parts of POSIX an application is using?

I've been given source code in C and want to see which parts (functions, system calls) of POSIX is used in it. Is there a test suite or other program, which can give me an overview?
Minix
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Open Group Base Specifications, Single UNIX Specification and POSIX

Possible Duplicate: What differences are between POSIX and Single UNIX Specification? Having asked about the relation between POSIX and Single UNIX Specification, I was now wondering what relation are between the Open Group Base Specifications,…
Tim
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