On Wed, Mar 08, 2000 at 08:07:23PM +0400, bear wrote:
> Hello Everybody.
> Can you tell me please, how I can create a two sided pipes in C++.
> I want to say can I run a program and get its output to stdout as
> input stream to my program & vice-versa?
>
> --
> Best regards,
> Areg mailto:[EMAIL PROTECTED]
kinda... I don't know how to in C++. but here's a C program
that does set up the pipes correctly. There's some kind of bug in the
reading/writing, but I believe the pipes are setup up correctly.
umm. you could probably also poke around in $CPLUSPLUSAPPLICATION source
code for an example.. KDE comes to mind(It's one of the few Linux things
I know is written in C++, and it probably uses pipes).
also to help you are
man 2 pipe
man 2 dup
you can make an fstream in c++ from a filedescriptor
by declaring
fstream suchandso(filedescriptor);
I think. Haven't been forced to write c++ for 6 months, so I'm pretty rusty
at it.
------------begin pipetest.c-----------
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <errno.h>
extern int errno;
int main ( void )
{
char buffer[8192];
int fd[2];
ssize_t test;
int childdone=0;
if (pipe(fd) == -1){
perror("Couldn't open pipe");
exit(EXIT_FAILURE);
}
switch (fork()){
case -1:
perror("Couldn't fork:");
close(fd[0]);
close(fd[1]);
exit(EXIT_FAILURE);
case 0: /* child */
close(STDIN_FILENO);
if (dup(fd[0])==-1){ /*new standard in*/
perror("[child]:Couldn't dup for stdin:");
close(fd[0]);
close(fd[1]);
exit(EXIT_FAILURE);
}
close(STDOUT_FILENO);
if (dup(fd[1])==-1){ /*new stdout*/
perror("[child]:Couldn't dup for stdout:");
close(fd[0]);
close(fd[1]);
exit(EXIT_FAILURE);
}
if(execl("/usr/bin/w","")==-1){
perror("[child]:couldn't execl");
close(fd[0]);
close(fd[1]);
exit(EXIT_FAILURE);
}else{
close(fd[0]);
close(fd[1]);
exit(EXIT_SUCCESS);
}
break;
default: /*parent*/
close(STDIN_FILENO);
if (dup(fd[0])==-1){
perror("[parent]:couldn't dup for stdout:");
close(fd[0]);
close(fd[1]);
exit(EXIT_FAILURE);
}
fcntl(STDIN_FILENO,F_SETFL,O_NONBLOCK);
close(STDOUT_FILENO);
if (dup(fd[1])==-1){
perror("[parent]:couldn't dup for stdin:");
close(fd[0]);
close(fd[1]);
exit(EXIT_FAILURE);
}
/* okay at this point a doubly ended pipe should be set up
* your programs stdout is the childs stdin and the childs stdout
* is your stdin
* enjoy
*/
/* the stuff after this doesn't work quite right,
* but that's okay... its just an example. doesn't
* have to be perfect :-)
*/
while ((test=read(fd[0],buffer,8191))){
if (test==-1){
if(errno==EAGAIN){
if (!childdone)
continue;
test=0;
break;
}
else
break;
}
buffer[test]='\0';
if(waitpid(0,0,WNOHANG)!=0)
childdone=1;
write(STDERR_FILENO,buffer,test);
}
if (test)
perror("read error:");
close(fd[0]);
close(fd[1]);
if (!test)
exit(EXIT_SUCCESS);
else
exit(EXIT_FAILURE);
}
return(-1);/*shouldn't be reached*/
}
--------------end pipetest------------------
have fun,
greg
--
dronf!
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