strange problem with /dev/isdninfo

[Joern Heissler]

Hello!
I'm new to the Mailinglist.

I've got a strange problem with /dev/isdninfo:

joern:~# cat /dev/isdninfo
idmap:  Hisax...
chmap: 0 1 ...
foo
bar
phone:  ??? ??? ...

--> cat /dev/isdninfo works :-)

Here's the problem:

joern:~# cat <<EOF >cat2.c
#include <unistd.h>
#include <fcntl.h>

int main(int argc, char **argv)
{
        char buf[500];
        int fd;

        if(argc!=2) {
                return(1);
        }
        fd=open(argv[1],O_RDONLY);
        write(1,buf,read(fd,buf,200));
        return(0);
}
EOF
joern:~# gcc -o cat2 -Wall -ansi cat2.c
joern:~# ./cat2 /dev/urandom ---> 200 bytes of random characters. works :-)
joern:~# ./cat2 /dev/isdninfo ---> nothing. 

joern:~# strace ./cat2 /dev/isdninfo
...
open("/dev/isdninfo", O_RDONLY) = 3
read(3, "", 200) = 0
write(1, "", 0) = 0
_exit(0) = ?


Could someone please tell me what's wrong? I (and some other people) do not understand 
this.
Thanks in advance!

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