ref: 75d6267a5f788162d92e7a5ae126cd8b0770aa8a
dir: /sys/src/libc/9sys/iounit.c/
#include <u.h>
#include <libc.h>
/*
* Format:
3 r M 4 (0000000000457def 11 00) 8192 512 /rc/lib/rcmain
*/
int
iounit(int fd)
{
int i, cfd;
char buf[128], *args[10];
snprint(buf, sizeof buf, "/fd/%dctl", fd);
cfd = open(buf, OREAD|OCEXEC);
if(cfd < 0)
return 0;
i = read(cfd, buf, sizeof buf-1);
close(cfd);
if(i <= 0)
return 0;
buf[i] = '\0';
if(tokenize(buf, args, nelem(args)) != nelem(args))
return 0;
return atoi(args[7]);
}