Shell Programming and Scripting

/* cisshPipe.c
 */

/* External functions --
 */
extern void error(char* message);
//extern wait(int*status);



/* cisshPipe(char* command1[], char* command2[])
 * handles command lines with pipes.
 */

#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

void
cisshPipe(char* command1[], char* command2[])
{
	pid_t pid;
	pid_t pid1;
	int status;
	int	commpipe[2];	/* This holds the input and output of the pipe */
	
	if(pipe(commpipe)){	/* Setup communication pipeline */ 
			fprintf(stderr,"Pipe error\n");
			exit(1);
	}
	
	if ( (pid = fork()) == -1 ){
		fprintf(stderr,"Fork error. Exiting.\n");	/* something went wrong with forking */
        }

		
	

	if (pid ==0) {
		// first child process
	
		

		close(commpipe[1]);
		dup2(commpipe[0],1);	/* Replace in side of pipe with stdout */
		close(commpipe[0]);
		execv(command1[0], command1);
		
		

		if ( (pid1 = fork()) == -1 ){
			fprintf(stderr,"Fork error. Exiting.\n");	/* something went wrong with forking */
		}

		if(pid1 == 0){
			/* second child process */

			close(commpipe[0]);
			dup2(commpipe[1],0);	/* Replace out side of pipe with stdin */
			close(commpipe[1]);
			execv(command2[0], command2);
					
		}
		
		else {
			
			close(commpipe[1]);
			close(commpipe[0]);
			

			if(wait(&status) < 0)
			{
	 			 error("cissh: error waiting for child.");
	 			 perror("wait");
			}	
			
		}	
	}


	else {

		


		close(commpipe[1]);
		close(commpipe[0]);
		

		if(wait(&status) < 0)
			{
	 			 error("cissh: error waiting for child.");
	 			 perror("wait");
			}			
	}
	
	
		
}

if ((pid0 = fork()) < 0) {
    error
}
if (pid0 == 0) {
    first child
} /* close brace here! */
if ((pid1 = fork()) < 0) {
    error
}
if (pid1 == 0) {
    second child
}
wait for children