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| From | glen herrmannsfeldt <gah@ugcs.caltech.edu> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: fseek under IBM MVS |
| Date | 2014-12-17 21:59 +0000 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <m6sub5$8e4$1@speranza.aioe.org> (permalink) |
| References | <m6kumm$sfe$1@speranza.aioe.org> <36760209-5dbc-417b-85bb-17993bbe5900@googlegroups.com> <549153d8.2327046@news.xs4all.nl> <lnvbladx5k.fsf@nuthaus.mib.org> |
Keith Thompson <kst-u@mib.org> wrote: > raltbos@xs4all.nl (Richard Bos) writes: (snip) >> Apart from the reliability issue, the fseek()/ftell() trick simply is >> inefficient, in a way that fstat()/filelength()/GetFileSize()/&c. >> aren't, if they're at all well implemented. > On a system where it works, I woudnl't expect the fseek()/ftell() trick > to be particularly inefficient. By works, you mean for a stream of bytes file system? For MVS, if you want the exact byte length, for variable length records, you have to read the whole file and count them. For FBS, you can read just the last track and count it. Disk addresses on MVS (back to OS/360) are eight bytes long, of the form MBBCCHHR where the important ones are CC (16 bit cylinder), HH (16 bit track within cylinder) and R (eight bit record within track). That is what you need to know to seek and read a block. The OS/360 ISAM put disk addresses inside the file, which complicated backups. Just copying the bytes wasn't enough, as the addresses would be wrong. Similar to what happens if you write C pointers to a file. Disk space is allocated in tracks or cylinders, not blocks. -- glen
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fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-14 22:16 +0100
Re: fseek under IBM MVS glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-15 01:12 +0000
Re: fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-15 09:13 +0100
Re: fseek under IBM MVS glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-15 09:22 +0000
Re: fseek under IBM MVS Kaz Kylheku <kaz@kylheku.com> - 2014-12-15 16:26 +0000
Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-17 09:58 +0000
Re: fseek under IBM MVS BartC <bc@freeuk.com> - 2014-12-17 11:29 +0000
Re: fseek under IBM MVS John Bode <jfbode1029@gmail.com> - 2014-12-15 10:35 -0800
Re: fseek under IBM MVS glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-15 21:33 +0000
Re: fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-15 23:45 +0100
Re: fseek under IBM MVS Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2014-12-15 17:56 -0500
Re: fseek under IBM MVS Kaz Kylheku <kaz@kylheku.com> - 2014-12-15 23:05 +0000
Re: fseek under IBM MVS BartC <bc@freeuk.com> - 2014-12-15 23:19 +0000
Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-15 16:36 -0800
Re: fseek under IBM MVS Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2014-12-15 20:42 -0500
Re: fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-16 01:00 +0100
Re: fseek under IBM MVS glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-16 01:09 +0000
Re: (OT) fseek under IBM MVS Vincenzo Mercuri <nomail@yahoo.it> - 2014-12-16 09:11 +0100
Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-17 10:06 +0000
Re: fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-17 11:33 +0100
Re: fseek under IBM MVS John Bode <jfbode1029@gmail.com> - 2014-12-17 08:48 -0800
Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-17 17:26 +0000
Re: fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-17 19:46 +0100
Re: fseek under IBM MVS Richard Heathfield <invalid@see.sig.invalid> - 2014-12-17 19:28 +0000
Re: fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-17 21:38 +0100
Re: fseek under IBM MVS Richard Heathfield <invalid@see.sig.invalid> - 2014-12-17 21:05 +0000
Re: fseek under IBM MVS Ian Collins <ian-news@hotmail.com> - 2014-12-18 11:37 +1300
Re: fseek under IBM MVS John Bode <jfbode1029@gmail.com> - 2014-12-17 12:43 -0800
Re: fseek under IBM MVS fir <profesor.fir@gmail.com> - 2014-12-19 08:35 -0800
Re: fseek under IBM MVS BartC <bc@freeuk.com> - 2014-12-19 16:51 +0000
Re: fseek under IBM MVS Robert Wessel <robertwessel2@yahoo.com> - 2014-12-19 16:36 -0600
Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-17 10:05 +0000
Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-17 09:05 -0800
Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-17 17:29 +0000
Re: fseek under IBM MVS John Bode <jfbode1029@gmail.com> - 2014-12-17 12:55 -0800
Re: fseek under IBM MVS John Bode <jfbode1029@gmail.com> - 2014-12-17 15:02 -0800
Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-17 23:37 +0000
Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-17 16:11 -0800
Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-18 12:06 +0000
Re: fseek under IBM MVS James Kuyper <jameskuyper@verizon.net> - 2014-12-18 11:44 -0500
Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-18 11:03 -0800
Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-19 11:31 +0000
Re: fseek under IBM MVS James Kuyper <jameskuyper@verizon.net> - 2014-12-19 08:03 -0500
Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-19 08:08 -0800
Re: fseek under IBM MVS James Kuyper <jameskuyper@verizon.net> - 2014-12-19 11:30 -0500
Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-17 15:56 -0800
Re: fseek under IBM MVS Ian Collins <ian-news@hotmail.com> - 2014-12-21 21:37 +1300
Re: fseek under IBM MVS glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-17 21:59 +0000
Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-17 14:33 -0800
Re: fseek under IBM MVS "Charles Richmond" <numerist@aquaporin4.com> - 2014-12-18 16:06 -0600
Re: fseek under IBM MVS Siri Crews <chine.bleu@yahoo.com> - 2014-12-17 04:20 -0800
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