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The Art of Unix Programming
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Unix Programming - Unix Standards - Unix Standards in the Open-Source World

Unix Standards in the Open-Source World

In the mid-1990s, the open-source community began standardization efforts of its own. These efforts built on the source-code-level compatibility secured by POSIX and its descendants. Linux, in particular, had been written from scratch in a way that depended on the availability of Unix API standards like POSIX.[146]

In 1998 Oracle ported its market-leading database product to Linux, in a move that was rightly seen as a major breakthrough in Linux's mainstream acceptance. The engineer in charge of the port provided a definitive demonstration that API standards had done their job when he was asked by a reporter what technical challenges Oracle had had to surmount. The engineer's reply was “We typed ‘make’.”

The problem for the new-school Unixes, therefore, was not API compatibility at the source-code level. Everybody took for granted the ability to move source code between different Linux, BSD, and proprietary-Unix distributions without more than a trivial amount of porting labor. The new problem was not source compatibility but binary compatibility. For the ground under Unix had shifted in a subtle way as a consequence of the triumph of commodity PC hardware.

In the old days, each Unix had run on what was effectively its own hardware platform. There was enough variety in processor instruction sets and machine architectures that applications had to be ported at source level to move at all. On the other hand, there were a relatively few major Unix releases, each with relatively long service lifetimes. Application vendors like Oracle could afford the cost of building and shipping separate binary distributions for each of three or four hardware/software combinations, because they could amortize the low cost of source-code porting over large customer populations and a long enough product life cycle.

But then the minicomputer and workstation vendors were swamped by inexpensive 386-based supermicros, and open-source Unixes changed the rules. Vendors found they no longer had a stable platform to ship their binaries to.

The superficial problem, at first, was the large number of Unix distributors — but as the Linux distribution market consolidated, it became clear that the real issue was the rate of change over time. APIs were stable, but the expected locations of system administrative files, utility programs, and things like the prefix of the paths to user mailbox names and system log files kept changing.

The first standards effort to develop within the new-school Linux and BSD community itself (beginning in 1993) was the Filesystem Hierarchy Standard (FHS). This was incorporated into the Linux Standards Base (LSB), which also standardized an expected set of service libraries and helper applications. Both standards became activities of the Free Standards Group, which by 2001 developed a role similar to X/Open's position amidst the old-school Unix vendors.



[144] The original 1986 trial-use standard was called IEEE-IX. The name ‘POSIX’ was suggested by Richard Stallman. The introduction to POSIX.1 says: “It is expected to be pronounced pahz-icks as in positive, not poh-six, or other variations. The pronounciation has been published in an attempt to promulgate a standardized way of referring to a standard operating system interface”.

[145] One Linux distributor, Lasermoon in Great Britain, did achieve POSIX.1 FIPS 151-2 certification — and went out of business, because potential customers didn't care.

[146] See Just for Fun [Torvalds] for discussion.


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The Art of Unix Programming
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