Re: How to do a blocking read() ?

Michael Kerrisk <michael.kerrisk.nospam@xxxxxxx> writes:
On Mon, 28 May 2007 17:01:51 -0700, Paul Pluzhnikov
<ppluzhnikov-nsp@xxxxxxxxxxx> wrote:
Charles Sullivan <cwsulliv@xxxxxxxxxxxx> writes:
The situation is that I have a background process which sporadically
writes short bursts of data to a spool file. The intention is that
another process have a routine which will sit and wait for new data
to become available, then read it.

I thought a blocking read() could do this - am I mistaken?

Yes, you are.

If you use a pipe (perhaps a named pipe), then read will block
until the data is available.

But if you insist on an on-disk file, then read will never block;
and you'll have to loop doing sleep and fstat, until file size
changes.

There is also a Linux-specific solution using dnotify.
See "man fcntl", search for F_NOTIFY.

But, if Linux specific, then since Linux 2.6.13, better is inotify --
see the inotify(7) man page.

One would assume that 'Linux application development' is quite
linux-specific. Apart from that, if inotify is any 'better' depends
mostly on portabilty requirements.
.

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