strange problem with /dev/isdninfo

strange problem with /dev/isdninfo

[Joern Heissler]

[-- Attachment #1: Type: text/plain, Size: 918 bytes --]

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!


[-- Attachment #2: Type: application/pgp-signature, Size: 240 bytes --]

Re: strange problem with /dev/isdninfo

[Kai Germaschewski]

On Wed, 21 Mar 2001, Joern Heissler wrote:

> I've got a strange problem with /dev/isdninfo:
> 
> joern:~# cat /dev/isdninfo
> idmap:  Hisax...
> chmap: 0 1 ...
>
> --> cat /dev/isdninfo works :-)
> 
> Here's the problem:
> 
> open("/dev/isdninfo", O_RDONLY) = 3
> read(3, "", 200) = 0
>
> Could someone please tell me what's wrong? I (and some other people) do not understand this.

Well, /dev/isdninfo will only return the info to you if it entirely fits
into the supplied buffer. So, you should try a read with 2048 bytes or so,
and it'll work just fine.

Not that I think that the current behavior is particularly smart, but
that's how things are.

--Kai