Trying to get a basic C shell to do a simple pipe() - c

Question

I am trying to create a simple c shell. The only thing I can't get to work is the piping. I just need one pipe (i.e. "ls | wc -l"). I can't find anything where someone does this by reading the arguments from command line, any help would be greatly appreciated. I need help getting a second set of arguments that is after the "|" right now if I had the argument "ls | wc -l" I would get "ls" stored in args2 but I need "wc -l" to be in args3 so I can execvp() them separately.
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <signal.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/wait.h>
#define HISTORY_COUNT 20
char *prompt = "% ";
int
main()
{
int pid;
//int child_pid;
char line[81];
char *token;
char *separator = " \t\n";
char **args;
char **args2;
char **args3;
char cmd[100];
char *hp;
char *cp;
char *ifile;
char *ofile;
int check;
int pfds[2];
int i;
int j;
int current = 0;
int p = 0;
//int check;
char *hist[HISTORY_COUNT];
//char history[90];
//typedef void (*sighandler_t) (int);
args = malloc(80 * sizeof(char *));
args2 = malloc(80 * sizeof(char *));
while (1) {
fprintf(stderr, "%s", prompt);
fflush(stderr);
if (fgets(line, 80, stdin) == NULL)
break;
// split up the line
i = 0;
while (1) {
token = strtok((i == 0) ? line : NULL, separator);
if (token == NULL)
break;
args[i++] = token;
/* build command array */
}
args[i] = NULL;
// assume no redirections
ofile = NULL;
ifile = NULL;
// split off the redirections
j = 0;
i = 0;
while (1) { //stackoverflow.com/questions/35569673
cp = args[i++];
if (cp == NULL)
break;
switch (*cp) {
case '<':
if (cp[1] == 0)
cp = args[i++];
else
++cp;
ifile = cp;
break;
case '>':
if (cp[1] == 0)
cp = args[i++];
else
++cp;
ofile = cp;
break;
case '|': //I need this case to put the commands following
the pipe into a variable
if(cp[1] ==0){
cp = args[i++];
printf("%s\n", cp);
if(pipe(pfds) == -1){
perror("Broken Pipe");
exit(1);
}
//args3[j++] = cp;
p = 1;
}
else{
++cp;
printf("DOES THIS HAPPEN\n");
//
}
break;
default:
args2[j++] = cp;
args3[cp++] = cp
break;
}
}
args2[j] = NULL;
if (j == 0)
continue;
switch (pid = fork()) {
case 0:
// open stdin
if (ifile != NULL) {
int fd = open(ifile, O_RDONLY);
if (dup2(fd, STDIN_FILENO) == -1) {
fprintf(stderr, "dup2 failed");
}
close(fd);
}
// open stdout
if (ofile != NULL) {
// args[1] = NULL;
int fd2;
if ((fd2 = open(ofile, O_WRONLY | O_CREAT, 0644)) < 0) {
perror("couldn't open output file.");
exit(0);
}
// args+=2;
printf("okay");
dup2(fd2, STDOUT_FILENO);
close(fd2);
}
if(p == 1){ //from stackoverflow.com/questions/2784500
printf("Welcome to the party\n");
close(1);
dup(pfds[1]);
close(pfds[0]);
execvp(args2[0], args2);
break;
}
if(strcmp(args2[0], "cd") == 0){ //cd command
if(args2[1] == NULL){
fprintf(stderr, "Expected argument");
}
else{
//printf("Is this happening");
check = chdir(args2[1]);
//printf("What abuot this");
if(check != 0){
fprintf(stderr,"%s",prompt);
}
}
break;
}
if (strcmp(args2[0], "history") == 0){
int i = 0;
int hist_num = 1;
//printf("%d\n", current);
do {
if (hist[i]) {
printf("%4d %s\n", hist_num, hist[i]);
hist_num++;
}
i = (i + 1) % HISTORY_COUNT;
} while (i != current);
break;
}
execvp(args2[0], args2); /* child */
signal(SIGINT, SIG_DFL);
fprintf(stderr, "ERROR %s no such program\n", line);
exit(1);
break;
case -1:
/* unlikely but possible if hit a limit */
fprintf(stderr, "ERROR can't create child process!\n");
break;
default:
//printf("am I here");
if(p==1){
close(0);
dup(pfds[0]);
close(pfds[1]);
//execvp();
}
wait(NULL);
//waitpid(pid, 0, 0);
}
}
exit(0);
}