On Fri, 22 May 2015 14:57:59 +0100, Jim Lesurf wrote:

In article
wwvlhggrcx4.fsf@l1AntVDjLrnP7Td3DQJ8ynzIq3lJMueXf 87AxnpFoA.invalid,
Richard Kettlewell wrote:

1. If the environment variable TMPDIR is set, use that instead of /tmp.

2. Don't use predictable filenames; /tmp is shared between multiple
users. (Get this wrong and you will introduce security problems.)

If you don't care about the filename, the easiest policy is to use
tmpfile(). That'll given you an anonymous file somewhere sensible.

I'm not clear how that would work for my requirement. I'm using system()
to launch flac and have it put its output into a file which I specify by
its name. Then my main program uses that name to fopen() the file and
read from it.

AIUI tmpfile() will give me a file 'handle' (FILE*) but no name. How
would I use that as part of the command string for flac?

I did find a man page for tmpname() but having given the details it says
to "Never use it!".

There are a couple of other ways to do this:

1) use a script to run flac and pipe its output directly into
your program like this:

flac inputfile | yourprogram


Your program will use a loop to copy bytes from flac's stdout stream
into a temporary file created using something like:

#include stdio.h
...
FILE flacfile = tmpfile();

This is a nameless file which will vanish when you close it or exit
from the program. You'd fill it by reading stdin and after that you
can reposition to its start by calling rewind() and read through the
file as many times as you want.

2) you can do more or less the same as above by using the fork/exec/wait
sequence instead of system() and read flac's stdout into a nameless
file created with tmpfile().

Sources like the aforementioned 'Lion book' give good guidance on
using fork/exec/wait


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
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