Paul Eggert wrote:
>If this is merely for debugging, can't you write a wrapper that forces
>line buffering for a program? The wrapper could substitute your own C
>library functions via LD_PRELOAD, or could run the program inside a
>pseudotty a la 'expect'.
>
>
No I was thinking of a more simple general solution,
rather than a once off complicated hack.
>If it's for production use then I'm not sure it's a good idea to slow
>down and complicate standard libraries and/or apps for a
>fairly-specialized need.
>
>
I thought it would be quite a common requirement to control stdio buffering.
why does grep have the --line-buffered option for example?
Usually where I notice the lack of control is in commands of the format:
`intermittend_output | blah1 | blah2` where blah1 buffers things up when
I don't want.
The following pseudo code is what I was thinking of,
to be run at the start of the appropriate applications (or ideally in
glibc):
for (fd=0; fd<3; fd++) { //getdtablesize maybe
if ((val = getenv("BUF_%d_" % fd))) {
if (fstat(fd) != 0) continue;
val = atoi(val);
if (val == 0) {
setvbuf(fd, (char*) NULL, _IONBF, 0);
} else if (val == 1) {
setvbuf(fd, (char*) NULL, _IOLBF, 0);
} else if (val > 1) {
char* buf = malloc(val);
setvbuf(fd, buf, _IOFBF, val);
}
}
}
thanks,
Pádraig.
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