OS2021_Project1.Shell/yeeshell.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <dirent.h>
#include <signal.h>
#include <errno.h>
#include <fcntl.h>
#include "yeeshell.h"

/* record cmdline history */
char *history[CMDLINE_HISTORY_MAX_QUANTITY];
int cmdline_amount = 0;

int main()
{
	char *cmdline = NULL, *pwd = NULL;
	char *args[ARGS_MAX_QUANTITY];
	int status = 1;
	pwd = (char *)calloc(PATH_MAX_SIZE, sizeof(char));
	for (int i = 0; i < CMDLINE_HISTORY_MAX_QUANTITY; i++)
	{
		history[i] = (char *)calloc(CMDLINE_MAX_SIZE, sizeof(char));
	}

	/* execute the shell's read, parse and execution loop */
	do
	{
		if (!getcwd(pwd, PATH_MAX_SIZE))
		{
			printf("yeeshell: The current path cannot be obtained!\n");
			exit(0);
		}
		printf("[root@yeeshell %s]# ", pwd);
		cmdline = readline();
		strcpy(history[cmdline_amount++], cmdline);
		status = execute(cmdline, args);
		free(cmdline);
	} while (status);
	for (int i = 0; i < CMDLINE_HISTORY_MAX_QUANTITY; i++)
	{
		free(history[i]);
	}
	exit(EXIT_SUCCESS);
}

char *readline()
{
	char *cmdline = NULL;
	ssize_t bufsize = 0;
	getline(&cmdline, &bufsize, stdin);
	return cmdline;
}

int parseline(char *cmdline, char **args)
{
	static char array[CMDLINE_MAX_SIZE]; /* holds local copy of command line */
	char *buf = array;					 /* ptr that traverses command line */
	char *delim;						 /* points to first space delimiter */
	int argc;							 /* number of args */
	int bg;								 /* background job? */

	strcpy(buf, cmdline);
	buf[strlen(buf) - 1] = ' ';	  /* replace trailing '\n' with space */
	while (*buf && (*buf == ' ')) /* ignore leading spaces */
	{
		buf++;
	}

	/* Build the argv list */
	argc = 0;
	if (*buf == '\'')
	{
		buf++;
		delim = strchr(buf, '\'');
	}
	else
	{
		delim = strchr(buf, ' ');
	}

	while (delim)
	{
		args[argc++] = buf;
		*delim = '\0';
		buf = delim + 1;
		while (*buf && (*buf == ' ')) /* ignore spaces */
		{
			buf++;
		}

		if (*buf == '\'')
		{
			buf++;
			delim = strchr(buf, '\'');
		}
		else
		{
			delim = strchr(buf, ' ');
		}
	}
	args[argc] = NULL;

	if (argc == 0) /* ignore blank line */
	{
		return 1;
	}

	/* should the job run in the background? */
	if ((bg = (*args[argc - 1] == '&')) != 0)
	{
		args[--argc] = NULL;
	}
	return bg;
}

int check_redirect(char **args, char *redirect_filename, char **redirect_args)
{
	int i = 0, j = 0, redirect_flag = REDIRECT_NO;
	while (args[i] != NULL)
	{
		if (!strcmp(args[i], ">"))
		{
			redirect_flag = REDIRECT_OUT;
			break;
		}
		else if (!strcmp(args[i], "<"))
		{
			redirect_flag = REDIRECT_IN;
			break;
		}
		i++;
	}

	if ((redirect_flag == 1) || (redirect_flag == 2))
	{
		strcpy(redirect_filename, args[i + 1]);
		for (j = 0; j < i; j++)
		{
			redirect_args[j] = args[j];
		}
	}

	return redirect_flag;
}

int do_redirect(int redirect_flag, char *redirect_filename, char **redirect_args)
{
	pid_t pid;
	int fd = 1;
	if ((pid = fork()) == 0) /* Child process */
	{
		if (redirect_flag == 1) /* in or out? */
		{
			fd = open(redirect_filename, O_CREAT | O_WRONLY | O_TRUNC, S_IRUSR | S_IWUSR | S_IXUSR);
			close(1);
			dup(fd);
		}
		else if (redirect_flag == 2)
		{
			fd = open(redirect_filename, O_RDONLY, S_IRUSR);
			close(0);
			dup(fd);
		}
		if (execvp(redirect_args[0], redirect_args) <= 0)
		{
			printf("%s: Command not found\n", redirect_args[0]);
			exit(0);
		}
		close(fd);
	}
	else /* parent process */
	{
		waitpid(pid, NULL, 0);
	}
	return 1;
}

int check_pipe(char **args, char **pipe_arg_1, char **pipe_arg_2)
{
	int pipe_flag = 0, i = 0, j = 0;

	while (args[i] != NULL)
	{
		if (!strcmp(args[i], "|"))
		{
			pipe_flag = 1;
			break;
		}
		pipe_arg_1[j++] = args[i++];
	}
	pipe_arg_1[j] = NULL;

	j = 0;
	i++;
	while (args[i] != NULL)
	{
		pipe_arg_2[j++] = args[i++];
	}
	pipe_arg_2[j] = NULL;
	return pipe_flag;
}

int do_pipe(char **pipe_arg_1, char **pipe_arg_2)
{
	int fds[2];
	pipe(fds);
	pid_t prog_1, prog_2;

	if ((prog_1 = fork()) == 0) /* Child process 1 */
	{
		close(1);
		dup(fds[1]);
		close(fds[0]);
		close(fds[1]);

		if (execvp(pipe_arg_1[0], pipe_arg_1) <= 0)
		{
			printf("%s: Command not found\n", pipe_arg_1[0]);
			exit(0);
		}
	}

	if ((prog_2 = fork()) == 0) /* Child process 1 */
	{

		dup2(fds[0], 0);
		close(fds[0]);
		close(fds[1]);

		if (execvp(pipe_arg_2[0], pipe_arg_2) <= 0)
		{
			printf("%s: Command not found\n", pipe_arg_2[0]);
			exit(0);
		}
	}

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

	waitpid(prog_1, NULL, 0);
	waitpid(prog_2, NULL, 0);
	return 1;
}

int do_bg_fg(char **args, int bg)
{
	pid_t pid;
	if ((pid = fork()) == 0)
	{
		if (execvp(args[0], args) <= 0)
		{
			printf("%s: Command not found\n", args[0]);
			exit(0);
		}
	}
	else
	{
		if (bg)
		{
			signal(SIGCHLD, SIG_IGN);
		}
		else
		{
			waitpid(pid, NULL, 0);
		}
	}
	return 1;
}

int execute(char *cmdline, char **args)
{
	int bg = 0, i = 0, redirect_flag = 0, pipe_num = 0;
	pid_t pid;
	char *redirect_filename = NULL;
	char *redirect_args[ARGS_MAX_QUANTITY];
	char *pipe_arg_1[ARGS_MAX_QUANTITY];
	char *pipe_arg_2[ARGS_MAX_QUANTITY];

	redirect_filename = (char *)calloc(REDIRECT_FILENAME_MAX_SIZE, sizeof(char));
	memset(redirect_args, NULL, sizeof(redirect_args));

	bg = parseline(cmdline, args);
	redirect_flag = check_redirect(args, redirect_filename, redirect_args);
	pipe_num = check_pipe(args, pipe_arg_1, pipe_arg_2);

	if (args[0] == NULL)
	{
		return 1;
	}
	if (pipe_num == 0) /* no pipe */
	{
		if (!built_in(args)) /* built-in cmd? */
		{
			if (redirect_flag != 0) /* redirection? */
			{
				return do_redirect(redirect_flag, redirect_filename, redirect_args);
			}
			else
			{
				return do_bg_fg(args, bg);
			}
		}
		else
		{
			return 1;
		}
	}
	else
	{
		return do_pipe(pipe_arg_1, pipe_arg_2);
	}
}

int built_in(char **args)
{
	if (!strcmp(args[0], "exit"))
	{
		exit(0);
	}
	else if (!strcmp(args[0], "cd"))
	{
		return builtin_cd(args);
	}
	else if (!strcmp(args[0], "history"))
	{
		return builtin_history(args);
	}
	else if (!strcmp(args[0], "mytop"))
	{
		int flag = builtin_mytop();
		if (flag == -1)
		{
			printf("yeeshell: unable to get memory info.\n");
		}
		else if (flag == -2)
		{
			printf("yeeshell: unable to get CPU info.\n");
		}
		return flag;
	}
	else
	{
		return 0;
	}
}

int builtin_cd(char **args)
{
	if (args[1] == NULL)
	{
		return 1;
	}
	else
	{
		if (chdir(args[1]) != 0)
		{
			perror("yeeshell");
		}
		return 1;
	}
}

int builtin_history(char **args)
{
	int n = 0;
	if (args[1] == NULL)
	{
		n = cmdline_amount;
	}
	else
	{
		n = atoi(args[1]) < cmdline_amount ? atoi(args[1]) : cmdline_amount;
	}
	printf("ID\tCommandline\n");
	for (int i = 0; i < n; i++)
	{
		printf("%d\t%s\n", i + 1, history[i]);
	}
	return 1;
}

int builtin_mytop()
{
	int memory_flag = 0, CPU_flag = 0;
	memory_flag = mytop_memory();
	CPU_flag = mytop_CPU();
	if (!memory_flag)
	{
		return -1;
	}
	else if (!CPU_flag)
	{
		return -2;
	}
	else
	{
		return 1;
	}
}

int mytop_memory()
{
	FILE *fp = NULL;
	int pagesize;
	long total = 0, free = 0, cached = 0;

	if ((fp = fopen("/proc/meminfo", "r")) == NULL)
	{
		return 0;
	}

	fscanf(fp, "%u %lu %lu %lu", &pagesize, &total, &free, &cached);
	fclose(fp);

	printf("memmory(KBytes):\t%ld total\t%ld free\t%ld cached\n", (pagesize * total) / 1024, (pagesize * free) / 1024, (pagesize * cached) / 1024);

	return 1;
}

int mytop_CPU()
{
}