POSIX - revision history

Dank: /* File descriptors */

2023-01-05T06:27:00Z

File descriptors

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 ==File descriptors==
-* <tt>pread(2)</tt> and <tt>pwrite(2)</tt> allow <tt>read(2)</tt>- and <tt>write(2)</tt>-like behavior on a file descriptor from a specified offset, without updating the offset. This allows for the atomic equivalent of an <tt>lseek(2)</tt> and an I/O, particularly useful when multiple threads are working with the same file descriptor (since file descriptor offset is shared across the process). Linux 2.1.69, glibc 2.1.
+* <tt>pread(2)</tt> and <tt>pwrite(2)</tt> allow <tt>read(2)</tt>- and <tt>write(2)</tt>-like behavior on a file descriptor from a specified offset, without updating the offset. This allows for the atomic equivalent of an <tt>lseek(2)</tt> and an I/O, particularly useful when multiple threads are working with the same file descriptor (since file descriptor offset is shared across the process). Linux 2.1.69, glibc 2.1, SVR4, POSIX.1-2001.
 ==File handles==
 * <tt>fileno(3)</tt> extracts the file descriptor from a [[ISO C|C]] <tt>FILE*</tt>. This will fail if <tt>FILE*</tt> is not associated with a descriptor. Examples include <tt>stdout</tt> and <tt>stderr</tt> in Microsoft Windows applications without a connected console, and a handle opened with POSIX's <tt>fmemopen(3)</tt> or <tt>open_memstream(3)</tt>.

Dank at 06:14, 5 January 2023

2023-01-05T06:14:19Z

← Older revision		Revision as of 06:14, 5 January 2023
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	"POSIX" may more-or-less mistakenly refer to...		"POSIX" may more-or-less mistakenly refer to...
	* [[Pthreads]], the POSIX threading API aka POSIX.1c		* [[Pthreads]], the POSIX threading API (aka POSIX.1c prior to POSIX.1-1997)
	* [[Linux APIs]], which ~~implement a portion of~~ POSIX		* [[Linux APIs]], which partially comply with POSIX
	* [[FreeBSD APIs]], which ~~implement a portion of~~ POSIX		* [[FreeBSD APIs]], which partially comply with POSIX
	* [[Shell]], which implements a portion of POSIX		* [[Shell]], which implements a portion of POSIX
	This page is about the "Systems Interfaces and Headers" defined in POSIX.1-2017 (aka IEEE Std 1003.1-2017 (Revision of IEEE Std 1003.1-2008) - IEEE Standard for Information Technology—Portable Operating System Interface (POSIX(R)) Base Specifications, Issue 7) APIs. Note that POSIX.1-2017 is equivalent to POSIX.1-2008 plus its two Technical Corrigenda.		This page is about the "Systems Interfaces and Headers" defined in POSIX.1-2017 (aka IEEE Std 1003.1-2017 (Revision of IEEE Std 1003.1-2008) - IEEE Standard for Information Technology—Portable Operating System Interface (POSIX(R)) Base Specifications, Issue 7) APIs. Note that POSIX.1-2017 is equivalent to POSIX.1-2008 plus its two Technical Corrigenda.

Dank at 06:13, 5 January 2023

2023-01-05T06:13:24Z

← Older revision		Revision as of 06:13, 5 January 2023
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	** The glibc implementation of this function, first specified by POSIX.1-2008, has changed over the years, and required several bugfixes.		** The glibc implementation of this function, first specified by POSIX.1-2008, has changed over the years, and required several bugfixes.
	** The API does not provide any means of getting a pointer to the buffer.		** The API does not provide any means of getting a pointer to the buffer.
			** The append behavior implies an O(size) scan for a zero byte.

Dank at 06:12, 5 January 2023

2023-01-05T06:12:09Z

← Older revision		Revision as of 06:12, 5 January 2023
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	POSIX may refer to...		"POSIX" may more-or-less mistakenly refer to...
	* [[Pthreads]], the POSIX threading API		* [[Pthreads]], the POSIX threading API aka POSIX.1c
	* [[Linux APIs]], which implement a portion of POSIX		* [[Linux APIs]], which implement a portion of POSIX
	* [[FreeBSD APIs]], which implement a portion of POSIX		* [[FreeBSD APIs]], which implement a portion of POSIX
	* [[Shell]], which implements a portion of POSIX		* [[Shell]], which implements a portion of POSIX
			This page is about the "Systems Interfaces and Headers" defined in POSIX.1-2017 (aka IEEE Std 1003.1-2017 (Revision of IEEE Std 1003.1-2008) - IEEE Standard for Information Technology—Portable Operating System Interface (POSIX(R)) Base Specifications, Issue 7) APIs. Note that POSIX.1-2017 is equivalent to POSIX.1-2008 plus its two Technical Corrigenda.

			==File descriptors==
			* <tt>pread(2)</tt> and <tt>pwrite(2)</tt> allow <tt>read(2)</tt>- and <tt>write(2)</tt>-like behavior on a file descriptor from a specified offset, without updating the offset. This allows for the atomic equivalent of an <tt>lseek(2)</tt> and an I/O, particularly useful when multiple threads are working with the same file descriptor (since file descriptor offset is shared across the process). Linux 2.1.69, glibc 2.1.
			==File handles==
			* <tt>fileno(3)</tt> extracts the file descriptor from a [[ISO C\|C]] <tt>FILE</tt>. This will fail if <tt>FILE</tt> is not associated with a descriptor. Examples include <tt>stdout</tt> and <tt>stderr</tt> in Microsoft Windows applications without a connected console, and a handle opened with POSIX's <tt>fmemopen(3)</tt> or <tt>open_memstream(3)</tt>.
			* <tt>fmemopen(3)</tt> creates a <tt>FILE*</tt> handle around a user-supplied buffer, enforcing <tt>mode</tt> similar to <tt>fopen(3)</tt>. If <tt>NULL</tt> is supplied, <tt>fmemopen(3)</tt> will attempt to allocate a buffer of the specified size. Using append mode will place the initial offset at the first zero byte of the buffer, or one past the size of the buffer if no zero bytes are found (I assume this only applies when the buffer is provided externally, rather than internally allocated?). Writing past the size of the buffer will result in an error.
			** The glibc implementation of this function, first specified by POSIX.1-2008, has changed over the years, and required several bugfixes.
			** The API does not provide any means of getting a pointer to the buffer.

Dank: POSIX disambiguation page

2012-05-29T02:56:19Z

POSIX disambiguation page

New page

POSIX may refer to...
* [[Pthreads]], the POSIX threading API
* [[Linux APIs]], which implement a portion of POSIX
* [[FreeBSD APIs]], which implement a portion of POSIX
* [[Shell]], which implements a portion of POSIX