On 30/06/11 00:42, Bruno Haible wrote:
> Pádraig Brady wrote:
>> The following shows I think that iconv is bypassing stdio and buffering
>> internally?
>>
>> (echo; sleep 3; echo) | ltrace iconv -f ASCII
>
> This is true for the glibc 'iconv' program. But stdbuf also does not work with
> 'iconv' from GNU libiconv, and this program uses stdio in a very simple form:
> It reads from stdin using fread(). It does *not* call setvbuf explicitly.
>
> $ (echo; sleep 3; echo) | ltrace iconv -f ASCII
> fread(0xffe1f110, 1, 4096, 0xf7df5420)
> = 2
> $ (echo Hello; sleep 3; echo World) | stdbuf iconv -f ASCII
> Hello
> World
>From stdbuf.c /* FIXME: Should we mandate at least one option? */
Anway I don't think that this works even if you specify -i0
because fread() only seems to return after feof() or ferror()
as demonstrated by interacting with the following run with ltrace.
#include <stdio.h>
int main(void)
{
setvbuf (stdin, NULL, _IONBF, 0);
setvbuf (stdout, NULL, _IONBF, 0);
char buf[BUFSIZ];
for (;;) {
size_t count = fread (buf,1,BUFSIZ,stdin);
fwrite (buf,1,count,stdin);
if (feof (stdin))
break;
}
return 0;
}
I guess glibc could return early if there were no partial records
(which there never will be with a size of 1).
It's a bit surprising it doesn't even given the
wording of the man page.
cheers,
Pádraig.
