I'm trying to implement a multiple pipe for my shell in C.
All I have is a pipe function that pipe a | b but not a | b | c.
int c[2];
int returnv;
pid_t id;
pipe(c);
pid = fork()) == 0
if (pid)
{
dup2(c[1], 0);
close(p[1]);
close(p[1]);
execvp(array(0), array);
}
if ((pid = fork()) == 0)
{
dup2(p[0], 1);
close(p(0));
close(p[0]);
returnv = execvp(array[0], array);
}
close(p[1]);
wait(NULL);
wait(NULL);
wait(NULL);
return returnv;
And this is a second version:
int i = 0;
while (i < x)
{
pipe(c);
if ((pid = fork()) == 0)
{
dup2(t[i], 1);
if (i < 2)
dup2(p[0], 1);
close(p[1]);
r= execvp(cmd[i][0], cmd[i]);
}
wait(NULL);
close(p[0]);
i += 1;
t[i] = p[1];
How can I add the little something that will make this code manage multiple pipe please ? Thanks a lot in advance !
Edit: according to your comment
To perform multiples pipes you need to store all your commands somewhere. That's why I used a tab of structure.
Check this new version maybe easier to understand
So first you need a tab or something to store all your commands:
int main()
{
char *ls[] = {"ls", NULL};
char *grep[] = {"grep", "pipe", NULL};
char *wc[] = {"wc", NULL};
char **cmd[] = {ls, grep, wc, NULL};
loop_pipe(cmd);
return (0);
}
Then the function who will run through the tab and launch everything
void loop_pipe(char ***cmd)
{
int p[2];
pid_t pid;
int fd_in = 0;
while (*cmd != NULL)
{
pipe(p);
if ((pid = fork()) == -1)
{
exit(EXIT_FAILURE);
}
else if (pid == 0)
{
dup2(fd_in, 0); //change the input according to the old one
if (*(cmd + 1) != NULL)
dup2(p[1], 1);
close(p[0]);
execvp((*cmd)[0], *cmd);
exit(EXIT_FAILURE);
}
else
{
wait(NULL);
close(p[1]);
fd_in = p[0]; //save the input for the next command
cmd++;
}
}
}
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