Shell script for input output redirection - c

Question

Hi I am writing a shell script for input output redirection. The code is as follows
int parse(void)
{
char *p; /* pointer to current word */
char *msg; /* error message */
nwds = 0;
p = strtok(line," \t");
while (p != NULL) {
if (nwds == NWORDS) {
msg = "Error: too many words.\n";
write(2 ,msg, strlen(msg));
return 0;
}
if (strlen(p) >= MAXWORDLEN) {
msg = "Error: Word too long.\n";
write(2, msg ,strlen(msg));
return 0;
}
if(*p == '<') /* check if input symbol is present*/
isInput = true;
if(*p == '>') /* check if Output symbol is present*/
isOutput = true;
if(isInput) {
p = strtok(NULL," \t"); /* get pointer to next word, if any */
input = p;
}
if(isOutput) {
p = strtok(NULL," \t"); /* get pointer to next word, if any */
output = p;
}
words[nwds] = p; /* save pointer to the word */
nwds++; /* increase the word count */
p = strtok(NULL," \t"); /* get pointer to next word, if any */
}
return 1;
}
The above code takes commands from inputs and validates the number of commands and word length. It also validates the input and output redirection characters and stores the files names in input and output character pointers
int execute(void)
{
int i, j;
int status;
char *msg;
pid_t child_pid;
int in;
int out;
if (execok() == 0) { /* is it executable? */
status = fork(); /* yes; create a new process */
if (status == -1) { /* verify fork succeeded */
perror("fork");
exit(1);
}
if (status == 0) { /* in the child process... */
words[nwds] = NULL; /* mark end of argument array */
if(input != NULL && output != NULL)
{
in = open (input, O_RDONLY);
out = open (output, O_TRUNC | O_CREAT | O_WRONLY, 0666);
if ((in <= 0) || (out <= 0))
{
fprintf (stderr, "Couldn't open a file\n");
exit (errno);
}
dup2(in, 0);
dup2(out, 1);
close(in);
close out);
}
status = execve(path,words,environ); /* try to execute it */
perror("execve"); /* we only get here if */
_exit(0); /* execve failed... */
}
/*------------------------------------------------*/
/* The parent process (the shell) continues here. */
/*------------------------------------------------*/
child_pid = wait(&status); /* wait for process to end */
if (v_opt) { /* display status? */
char emsg[100];
if (WIFEXITED(status))
sprintf(emsg,"Child process %u exited with status %d.\n",
child_pid, WEXITSTATUS(status));
else
sprintf(emsg,"Child process %u did not exit normally.\n",
child_pid);
write(1,emsg,strlen(emsg));
}
} else {
/*----------------------------------------------------------*/
/* Command cannot be executed. Display appropriate message. */
/*----------------------------------------------------------*/
msg = "Error: '";
write(2,msg,strlen(msg));
write(2,words[0],strlen(words[0]));
msg = "' cannot be executed.\n";
write(2,msg,strlen(msg));
}
}
This is the execute function which performs redirection.
I am new to shell scripting, I gained some knowledge by going through the web and coded this program. This program is not redirecting the input and output. Could you please help me with this