Is a successful call to write(2) atomic?
johnl at iecc.com
Wed Jun 16 01:26:09 UTC 2021
It appears that Ronald F. Guilmette <rfg at tristatelogic.com> said:
>More to the point, if indeed each call to write() *is* "atomic"... at least
>in the sense that the given buffer will be treated like an indivisable whole,
>all of the way along its journey to some physical device... then why are
>users nontheless being encouraged, still, to "use some form of concurrency
>control"? I mean what would be the point of that if in fact write() never
>busts up the hunks of data given to it into separate sub-hunks?
I think it depends on the device. If I just want to write stuff to a log
file and not get it scrambled, this should do the trick:
fd = open("somefile", O_CREAT|O_WRONLY|O_APPEND);
/* put some stuff in buf */
write(fd, buf, strlen(buf)): /* O_APPEND ensures it's added at the end */
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