truncating a file opened via open()

[Ken Turkowski]

In article <340 at cmu-cs-edu1.ARPA> hua at cmu-cs-edu1.ARPA (Ernest Hua) writes:
>Does anyone have any idea how to truncate a file at the current point in
>writing if it is opened by open()?  I cannot use creat() because the file
>is being used by another process, and I cannot use unlink() it is likely
>that it is linked.  If the updated contents is longer than the original,
>it is not a problem because the file length is just extended.  But if the
>updated contents is shorter, the file does not shrink.  We have 4.1BSD on
>several 780's and 750's.

try

size = lseek(fd, 0L, 1);	/* tell(fd) */
ftruncate(fd, size);		/* int fd, size; */

It's yet another undocumented feature on 4.2.
-- 

Ken Turkowski @ CADLINC, Menlo Park, CA
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