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From: boyd@necisa.ho.necisa.oz (Boyd Roberts)
Newsgroups: comp.unix.admin
Subject: Re: What action updates a file's ACCESS time?
Keywords: file access time
Message-ID: <1958@necisa.ho.necisa.oz>
Date: 10 Dec 90 03:05:28 GMT
References: <331@twg.bc.ca> <1990Nov23.102257.10747@cnix.uucp> <893@jonlab.UUCP>
Organization: NEC Information Systems Australia Pty. Ltd.
Lines: 26

In article <893@jonlab.UUCP> jon@jonlab.UUCP (Jon H. LaBadie) writes:
>In article <331@twg.bc.ca> bill@twg.bc.ca (Bill Irwin) writes:
>>I would like to know ALL the possible activities that could result in a file's
>>access  time (ls -lu) being updated.
>

Reading the data in the file update its access time.

>Note also that write's to a file require a read first.  You may want to
>write one character.  But disks transfer data in blocks.  Thus, to
>write your one character, the block it will be written in must be read
>into memory.  You will "write" your one character into that memory
>buffer and the entire block will be written to disk.
>
>Thus writes also update access times.
>

No, that read is not always neccessary.  If the write spans the block no read
is neccessary.  Should a read be necessary, the read happens invisibly in that
the access time is not changed.  That read is not a true access of the file.
It's a side affect of the file-system implementation.


Boyd Roberts			boyd@necisa.ho.necisa.oz.au

``When the going gets wierd, the weird turn pro...''