can some elaborate the difference between sysread/read sysseek/seek

[lightoverhead]

Dear Monks

I am sort of confused about sysread/read, sysseek/seek.

It seems there is no practical difference between these functions.

Could someone enlighten me a bit? Thanks

[davido]

See also read and sysread.

[wjw]

Have never used either, but the way I read the docs

sysseek

and

sysread

implies that one
(seek) gets you to a place in the file measured in position units(unicode or bytes) and returns success or not,
and the other (read)
reads from that place for some length in position units(unicode or bytes).


So one gets you to where you want to start, and the other returns scalar data from the start position up to the length you ask for... Hope that is helpful...

[Marshall]

sysread() is normally used for very low level I/O.
Normally in Perl, you shouldn't be doing that.
This is possible, but there are buffering complications.

read() and seek() are much more normal.
Do not mix read, seek or sysread and sysseek together.

[ikegami]

sysread doesn't buffer. read buffers. On the rare occasions you need unbuffered IO (e.g. you want to use select), you need to use sysread and sysseek. (As such, sysread will always return as soon as data is available, if is there is data available than requested.) The rest of the time, you want to use read and seek.

[vsespb]

sysread could also returns errors like EINTR.