CSCI 480 assignment 3

//Terina Burr
//
#include <iostream>
#include <algorithm>
#include <string>
#include <cstring>
#include <sstream>
#include <vector>
#include <utility>
#include <iterator>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <cstdlib>
#include <cstdio>
using namespace std;
/********************************************************************************
FUNCTION: get_cmds

ARGUMENTS: const string& s - string to split
const string& delim - delimiter

RETURNS: vector<char*> - container of the new strings

NOTES: parses string of commands, spliting string by delimiter
********************************************************************************/
vector<string> get_cmds(const string& s, const string& delim)
{
stringstream ss(s);
vector<string> commands;
string t;
while(getline(ss >> ws, t, delim[0]))
{
commands.push_back(t);
ss >> t;//skip delimiter
}
return commands;
}

/********************************************************************************
FUNCTION: split_to_cstr

ARGUMENTS: const string& - string to split

RETURNS: vector<char*> - container of the new strings

NOTES: splits string by whitespace
********************************************************************************/
vector<char*> split_to_cstr(const string& s)
{
stringstream ss(s);

string t;
vector<char*> args_cmd;

while(ss >> t)//split by whitespace
{
args_cmd.push_back(new char[t.length() + 1]);//allocate
strcpy(args_cmd.back(), t.c_str());//copy
}
return args_cmd;
}

/********************************************************************************
FUNCTION: execute_cmds

ARGUMENTS: int fd[2] - array of file descriptors
vector<string>& - vector of commands

RETURNS: none

NOTES: fork new process for each command in vector and execute it
********************************************************************************/
void execute_cmds(int fd[2], const vector<string>& commands)
{
for(size_t i = 0; i < commands.size(); ++i)
{
int pid = fork();

vector<char*> cmd_args;
cmd_args = split_to_cstr(commands[i]);

if(pid == 0)
{
if(i == 0)//first command
{
if(commands.size() > 1)
{
close(fd[0]);
dup2(fd[1], 1);
//close(fd[1]);
}
}
else if(i == commands.size() - 1)//last command
{
close(fd[1]);
dup2(fd[0], 0);
//close(fd[0]);
}
else//inner commands
{
dup2(fd[0], 0);
//close(fd[0]);
dup2(fd[1], 1);
//close(fd[1]);
}
if(commands[i] == "q" || commands[i] == "quit")
{
//exit(-1);
kill(pid, SIGTERM);//kill process and send sig
}
if(execvp(cmd_args[0], &cmd_args[0]) < 0)
{
perror("could'nt execute"); //print error
exit(127);
}
}
else if(pid < 0)
{
perror("fork");
exit(EXIT_FAILURE);
}
}
}

int main()
{
string prompt("microshell>"),
input;
int fd[2];

while(cout << prompt && getline(cin, input))
{
if(pipe(fd) < 0)
{
perror("pipe");
exit(EXIT_FAILURE);
}

vector<string> commands(get_cmds(input, "||"));

execute_cmds(fd, commands);

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

//wait for children to finish
int pid, status;
while ((pid = wait(&status)) != -1) ;
}
}