t-h2o/microshell

Examen 4

Examen 04

Table of Contents

• 1. Usage
• 2. main
• 3. microshell
• 4. find the command
• 5. Init pipe
• 6. Execution

The repository: t-h2o/microshell

Microshell

1. Usage

• You have to use the absolute path

• You can only use ; (command separtor) or | (pipe)

./micro /bin/ls ";" /bin/ls -la

2. main

int	main(int argc, char **argv, char **envp)
{
	if (argc == 1)
		return 0;

	++argv;

	return microshell(argv, envp);
}

3. microshell

static int	microshell(char **arguments, char **envp)
{
	t_command	cmd;

	while (*arguments)
	{
		cmd.isPipe = 0;
		cmd.bin = *arguments;
		cmd.args = arguments;
		find_command(&arguments, &cmd);
		init_pipe(&cmd);
		if (cd_command(&cmd))
			execute_command(&cmd, envp);
	}

	return 0;
}

4. find the command

static void	find_command(char ***arguments, t_command *cmd)
{
	int	index;

	index = 0;
	while ((*arguments)[index]
		&& strcmp((*arguments)[index], ";")
		&& strcmp((*arguments)[index], "|"))
		++index;
	if ((*arguments)[index] == 0)
	{
		*arguments = &((*arguments)[index]);
		return ;
	}
	if (!strcmp((*arguments)[index], "|"))
		cmd->isPipe = 1;
	(*arguments)[index] = 0;
	*arguments = &((*arguments)[index + 1]);
}

5. Init pipe

static void	init_pipe(t_command *cmd)
{
	if (!(cmd->isPipe))
		return ;
	if (pipe(cmd->fd) == -1)
	{
		print_error("microshell: error: pipe\n");
		exit(1);
	}
}

6. Execution

static void	execute_command(t_command *cmd, char **envp)
{
	int	pid;

	pid = fork();

	if (pid == 0)
	{
		if (cmd->isPipe)
		{
			dup2(cmd->fd[1], 1);
			close(cmd->fd[1]);
			close(cmd->fd[0]);
		}
		if (execve(cmd->bin, cmd->args, envp) == -1)
		{
			print_error("microshell: Error execve\n");
			exit(1);
		}
	}
	else
	{
		if (cmd->isPipe)
		{
			dup2(cmd->fd[0], 0);
			close(cmd->fd[0]);
			close(cmd->fd[1]);
		}
		waitpid(pid, 0, 0);
	}
}