Re: popen2 popen call

[F. Heitkamp]

Ulrich Drepper wrote:
> On Thu, Aug 27, 2009 at 11:39,<heitkamp@xxxxxxxxxxxxx>  wrote:
>    
> > OK.  I read in one of the messages, that glibc, passes the popen call to a ABI in the kernel. I have not
> > looked at the code in glibc yet.
> >      
>
> popen uses pipe2.  There is fallback code to use pipe if necessary.
> It's compiled out only of the libc assumes the kernel support is
> available.
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
>
>    
OK.  I think I found the problem but how do I fix it?
Did I miss a kernel config option?
I got the code from the man page:
http://linux.die.net/man/2/pipe
http://manpages.courier-mta.org/htmlman2/pipe.2.html

bash-4.0$ gcc -o linux-pipe linux-pipe.c
/tmp/ccHHOYkD.o: In function `main':
linux-pipe.c:(.text+0x3b): warning: warning: pipe2 is not implemented 
and will always fail
bash-4.0$ ./linux-pipe ls
pipe: Function not implemented
bash-4.0$


#include <sys/wait.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
int
main(int argc, char *argv[])
{
    int pfd[2];
    pid_t cpid;
    char buf;
    assert(argc == 2);
    if (pipe2(pfd) == -1) { perror("pipe"); exit(EXIT_FAILURE); }
    cpid = fork();
    if (cpid == -1) { perror("fork"); exit(EXIT_FAILURE); }
    if (cpid == 0) {    /* Child reads from pipe */
        close(pfd[1]);          /* Close unused write end */
        while (read(pfd[0], &buf, 1) > 0)
            write(STDOUT_FILENO, &buf, 1);
        write(STDOUT_FILENO, "\n", 1);
        close(pfd[0]);
        _exit(EXIT_SUCCESS);
    } else {            /* Parent writes argv[1] to pipe */
        close(pfd[0]);          /* Close unused read end */
        write(pfd[1], argv[1], strlen(argv[1]));
        close(pfd[1]);          /* Reader will see EOF */
        wait(NULL);             /* Wait for child */
        exit(EXIT_SUCCESS);
    }
}

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/