Simple-Multiprocessing-Shell/command.cpp at main · garyhtou/Simple-Multiprocessing-Shell · GitHub

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#include"command.h"
#include"helper.h"

#include<iostream>
#include<unistd.h>
#include<vector>
#include<string>
#include<cstring>

usingnamespacestd;

string rawCommand;
int *inPipe;
int *outPipe;

Command::Command(string rawCommand)
{
this->rawCommand = rawCommand;

// Default to no pipes (for single commands)
this->inPipe = NULL;
this->outPipe = NULL;
}
Command::Command(string rawCommand, int *inPipe, int *outPipe)
{
this->rawCommand = rawCommand;
this->inPipe = inPipe;
this->outPipe = outPipe;
}
voidCommand::run()
{
// Get the command's arguments by lexing the raw command with the delimiter
	vector<string> args = Helper::lex(this->rawCommand, DELIMITER);

try
	{
// Execute the command!!
execute(args);
	}
catch (...)
	{
 cout << "Error: Command failed to run" << endl;
	}
}

voidCommand::execute(vector<string> args)
{
// Fork the current process
pid_t pid = fork();

if (pid == 0) // CHILD PROCESS
	{
this->childExecute(args);
// The child will exit in the function. It will never return here.
	}

// PARENT PROCESS
// Handle failed fork
if (pid < 0)
	{
 cout << "Error: Fork failed" << endl;

// Critical error. Exit program on fork failure
exit(1);
	}

// Close pipes
if (this->inPipe != NULL)
	{
close(this->inPipe[0]);
close(this->inPipe[1]);
	}

// Don't wait for child process to exit here. Only wait for child processes
// after ALL commands have been ran (forked and executed).
}

voidCommand::childExecute(vector<string> args)
{
// Convert the C++ vector of strings to C array
char *const *argv = Command::stringVectorToCharArray(args);

// If this command requires an input pipe, then set it up
if (this->inPipe)
	{
setInPipe(this->inPipe);
	}

// If this command requires an output pipe, then set it up
if (this->outPipe)
	{
setOutPipe(this->outPipe);
	}

// Execute the command!
execvp(argv[0], argv);

// A successful execvp call will NOT return. This following code will only run
// if an error with execvp occurs.
// Errors from the command executed are handled after waitpid.

// Deallocate argv (necessary if execvp fails)
for (size_t i = 0; i < args.size(); i++)
	{
delete[] argv[i];
	}
delete[] argv;

perror("Command failed to run");
exit(1);
}

voidCommand::setInPipe(int *input)
{
// Duplicate the file descriptor and close the previous file descriptor
if (int(dup2(input[0], STDIN_FILENO)) == -1)
	{
 cout << "Error: dup2 failed" << endl;
	};
if (int(close(input[0])) == -1)
	{
 cout << "Error: close system call failed" << endl;
	};
if (int(close(input[1])) == -1)
	{
 cout << "Error: close system call failed" << endl;
	};
}

voidCommand::setOutPipe(int *output)
{
// Duplicate the file descriptor and close the previous file descriptor
if (int(dup2(output[1], STDOUT_FILENO)) == -1)
	{
 cout << "Error: dup2 failed" << endl;
	};
if (int(close(output[0])) == -1)
	{
 cout << "Error: close system call failed" << endl;
	};
if (int(close(output[1])) == -1)
	{
 cout << "Error: close system call failed" << endl;
	};
}

char *const *Command::stringVectorToCharArray(vector<string> toConvert)
{
// Create an array of C strings
// Alot one extra element for the null terminator
char **charArr = newchar *[toConvert.size() + 1];

// Convert each C++ String to a C string and store in the array
for (size_t i = 0; i < toConvert.size(); i++)
	{
 charArr[i] = newchar[toConvert[i].size() + 1]; // make it fit
strcpy(charArr[i], toConvert[i].c_str()); // copy string
	}

// NULL terminate the array
	charArr[toConvert.size()] = (char *)NULL;

return charArr;
}