Multi-Process Shell in C, using Pipes [Linux] - c

Question

I'm trying to code a shell in C that supports multi-pipe process handling, depending on the amount of separate processes given by the user, and each separated by a "|" symbol. The shell forks the amount of processes into a child for each process.
Here's an example:
texto1.txt = "Isto é o Texto 1"
$ cat texto1.txt | grep -c Isto
result: 1
But I'm having trouble with communicating between children and finally to the parent process.
Here's my current code for the execpipe function, which executes the pipe process, being argv1 and argv2 the 2 separate processes given by user input: (Example: ls -l | wc -l)
int execpipe(char ** argv1, char ** argv2)
{
int fds[2];
pipe(fds);
int i;
pid_t p1, p2;
p1 = fork();
if (p1 == -1)
{ // error
char * error = strerror(errno);
printf("error fork!!\n");
return 1;
}
if (p1 == 0)
{ // child process
close(fds[0]);
dup2(fds[1], STDOUT_FILENO);
close(fds[1]);
if(execvp(argv1[0], argv1)<0){ // run command AFTER pipe character in userinput
char * error = strerror(errno);
printf("unknown command\n");
return 0;
}
}
else
{ // parent process
p2 = fork();
if(p2==0){
close(fds[1]);
dup2(fds[0], STDIN_FILENO);
close(fds[0]);
if(execvp(argv2[0], argv2)<0){ // run command AFTER pipe character in userinput
char * error = strerror(errno);
printf("unknown command\n");
return 0;
}
}else{ //Parent waits for both of it's children
wait(NULL);
wait(NULL);
}
}
}

Answer 1

The parent must close the pipe's write end to indicate the second process that no more data will come:
}
}else{ //Parent waits for both of it's children
close(fds[1]); // ++ add this line
wait(NULL);
wait(NULL);
}
Little note: instead of
char * error = strerror(errno);
printf("error fork!!\n");
why not
perror("fork");