sh.c

/* vi: set sw=4 ts=4: */
/*
 * lash -- the BusyBox Lame-Ass SHell
 *
 * Copyright (C) 2000 by Lineo, inc.
 * Written by Erik Andersen <andersen@lineo.com>, <andersee@debian.org>
 *
 * Based in part on ladsh.c by Michael K. Johnson and Erik W. Troan, which is
 * under the following liberal license: "We have placed this source code in the
 * public domain. Use it in any project, free or commercial."
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */

#include "internal.h"
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <glob.h>
#include <signal.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
#include <unistd.h>
#ifdef BB_FEATURE_SH_COMMAND_EDITING
#include "cmdedit.h"
#endif


#define JOB_STATUS_FORMAT "[%d] %-22s %.40s\n"


enum redirectionType { REDIRECT_INPUT, REDIRECT_OVERWRITE,
	REDIRECT_APPEND
};

struct jobSet {
	struct job *head;			/* head of list of running jobs */
	struct job *fg;				/* current foreground job */
};

struct redirectionSpecifier {
	enum redirectionType type;	/* type of redirection */
	int fd;						/* file descriptor being redirected */
	char *filename;				/* file to redirect fd to */
};

struct childProgram {
	pid_t pid;					/* 0 if exited */
	char **argv;				/* program name and arguments */
	int numRedirections;		/* elements in redirection array */
	struct redirectionSpecifier *redirections;	/* I/O redirections */
	glob_t globResult;			/* result of parameter globbing */
	int freeGlob;				/* should we globfree(&globResult)? */
	int isStopped;				/* is the program currently running? */
};

struct job {
	int jobId;					/* job number */
	int numProgs;				/* total number of programs in job */
	int runningProgs;			/* number of programs running */
	char *text;					/* name of job */
	char *cmdBuf;				/* buffer various argv's point into */
	pid_t pgrp;					/* process group ID for the job */
	struct childProgram *progs;	/* array of programs in job */
	struct job *next;			/* to track background commands */
	int stoppedProgs;			/* number of programs alive, but stopped */
};

struct builtInCommand {
	char *cmd;					/* name */
	char *descr;				/* description */
	char *usage;				/* usage */
	int (*function) (struct job *, struct jobSet * jobList);	/* function ptr */
};

/* Some function prototypes */
static int shell_cd(struct job *cmd, struct jobSet *junk);
static int shell_env(struct job *dummy, struct jobSet *junk);
static int shell_exit(struct job *cmd, struct jobSet *junk);
static int shell_fg_bg(struct job *cmd, struct jobSet *jobList);
static int shell_help(struct job *cmd, struct jobSet *junk);
static int shell_jobs(struct job *dummy, struct jobSet *jobList);
static int shell_pwd(struct job *dummy, struct jobSet *junk);
static int shell_export(struct job *cmd, struct jobSet *junk);
static int shell_source(struct job *cmd, struct jobSet *jobList);
static int shell_unset(struct job *cmd, struct jobSet *junk);

static void checkJobs(struct jobSet *jobList);
static int getCommand(FILE * source, char *command);
static int parseCommand(char **commandPtr, struct job *job, int *isBg);
static int setupRedirections(struct childProgram *prog);
static int runCommand(struct job newJob, struct jobSet *jobList, int inBg);
static int busy_loop(FILE * input);


/* Table of built-in functions */
static struct builtInCommand bltins[] = {
	{"bg", "Resume a job in the background", "bg [%%job]", shell_fg_bg},
	{"cd", "Change working directory", "cd [dir]", shell_cd},
	{"env", "Print all environment variables", "env", shell_env},
	{"exit", "Exit from shell()", "exit", shell_exit},
	{"fg", "Bring job into the foreground", "fg [%%job]", shell_fg_bg},
	{"jobs", "Lists the active jobs", "jobs", shell_jobs},
	{"pwd", "Print current directory", "pwd", shell_pwd},
	{"export", "Set environment variable", "export [VAR=value]", shell_export},
	{"unset", "Unset environment variable", "unset VAR", shell_unset},
	{".", "Source-in and run commands in a file", ". filename", shell_source},
	{"help", "List shell built-in commands", "help", shell_help},
	{NULL, NULL, NULL, NULL}
};

static const char shell_usage[] =

	"sh [FILE]...\n\n" "The BusyBox command interpreter (shell).\n\n";


static char cwd[1024];
static char *prompt = "# ";

#ifdef BB_FEATURE_SH_COMMAND_EDITING
void win_changed(int sig)
{
	struct winsize win = { 0, 0 };
	ioctl(0, TIOCGWINSZ, &win);
	if (win.ws_col > 0) {
		cmdedit_setwidth( win.ws_col - 1);
	}
}
#endif


/* built-in 'cd <path>' handler */
static int shell_cd(struct job *cmd, struct jobSet *junk)
{
	char *newdir;

	if (!cmd->progs[0].argv[1] == 1)
		newdir = getenv("HOME");
	else
		newdir = cmd->progs[0].argv[1];
	if (chdir(newdir)) {
		printf("cd: %s: %s\n", newdir, strerror(errno));
		return FALSE;
	}
	getcwd(cwd, sizeof(cwd));

	return TRUE;
}

/* built-in 'env' handler */
static int shell_env(struct job *dummy, struct jobSet *junk)
{
	char **e;

	for (e = environ; *e; e++) {
		fprintf(stdout, "%s\n", *e);
	}
	return (0);
}

/* built-in 'exit' handler */
static int shell_exit(struct job *cmd, struct jobSet *junk)
{
	if (!cmd->progs[0].argv[1] == 1)
		exit TRUE;

	else
		exit(atoi(cmd->progs[0].argv[1]));
}

/* built-in 'fg' and 'bg' handler */
static int shell_fg_bg(struct job *cmd, struct jobSet *jobList)
{
	int i, jobNum;
	struct job *job=NULL;

	if (!jobList->head) {
		if (!cmd->progs[0].argv[1] || cmd->progs[0].argv[2]) {
			fprintf(stderr, "%s: exactly one argument is expected\n",
					cmd->progs[0].argv[0]);
			return FALSE;
		}
		if (sscanf(cmd->progs[0].argv[1], "%%%d", &jobNum) != 1) {
			fprintf(stderr, "%s: bad argument '%s'\n",
					cmd->progs[0].argv[0], cmd->progs[0].argv[1]);
			return FALSE;
			for (job = jobList->head; job; job = job->next) {
				if (job->jobId == jobNum) {
					break;
				}
			}
		}
	} else {
		job = jobList->head;
	}

	if (!job) {
		fprintf(stderr, "%s: unknown job %d\n",
				cmd->progs[0].argv[0], jobNum);
		return FALSE;
	}

	if (*cmd->progs[0].argv[0] == 'f') {
		/* Make this job the foreground job */
		if (tcsetpgrp(0, job->pgrp))
			perror("tcsetpgrp");
		jobList->fg = job;
	}

	/* Restart the processes in the job */
	for (i = 0; i < job->numProgs; i++)
		job->progs[i].isStopped = 0;

	kill(-job->pgrp, SIGCONT);

	job->stoppedProgs = 0;

	return TRUE;
}

/* built-in 'help' handler */
static int shell_help(struct job *cmd, struct jobSet *junk)
{
	struct builtInCommand *x;

	fprintf(stdout, "\nBuilt-in commands:\n");
	fprintf(stdout, "-------------------\n");
	for (x = bltins; x->cmd; x++) {
		fprintf(stdout, "%s\t%s\n", x->cmd, x->descr);
	}
	fprintf(stdout, "\n\n");
	return TRUE;
}

/* built-in 'jobs' handler */
static int shell_jobs(struct job *dummy, struct jobSet *jobList)
{
	struct job *job;
	char *statusString;

	for (job = jobList->head; job; job = job->next) {
		if (job->runningProgs == job->stoppedProgs)
			statusString = "Stopped";
		else
			statusString = "Running";

		printf(JOB_STATUS_FORMAT, job->jobId, statusString, job->text);
	}
	return TRUE;
}


/* built-in 'pwd' handler */
static int shell_pwd(struct job *dummy, struct jobSet *junk)
{
	getcwd(cwd, sizeof(cwd));
	fprintf(stdout, "%s\n", cwd);
	return TRUE;
}

/* built-in 'export VAR=value' handler */
static int shell_export(struct job *cmd, struct jobSet *junk)
{
	int res;

	if (!cmd->progs[0].argv[1] == 1) {
		return (shell_env(cmd, junk));
	}
	res = putenv(cmd->progs[0].argv[1]);
	if (res)
		fprintf(stdout, "export: %s\n", strerror(errno));
	return (res);
}

/* Built-in '.' handler (read-in and execute commands from file) */
static int shell_source(struct job *cmd, struct jobSet *junk)
{
	FILE *input;
	int status;

	if (!cmd->progs[0].argv[1] == 1)
		return FALSE;

	input = fopen(cmd->progs[0].argv[1], "r");
	if (!input) {
		fprintf(stdout, "Couldn't open file '%s'\n",
				cmd->progs[0].argv[1]);
		return FALSE;
	}

	/* Now run the file */
	status = busy_loop(input);
	return (status);
}

/* built-in 'unset VAR' handler */
static int shell_unset(struct job *cmd, struct jobSet *junk)
{
	if (!cmd->progs[0].argv[1] == 1) {
		fprintf(stdout, "unset: parameter required.\n");
		return FALSE;
	}
	unsetenv(cmd->progs[0].argv[1]);
	return TRUE;
}

/* free up all memory from a job */
static void freeJob(struct job *cmd)
{
	int i;

	for (i = 0; i < cmd->numProgs; i++) {
		free(cmd->progs[i].argv);
		if (cmd->progs[i].redirections)
			free(cmd->progs[i].redirections);
		if (cmd->progs[i].freeGlob)
			globfree(&cmd->progs[i].globResult);
	}
	free(cmd->progs);
	if (cmd->text)
		free(cmd->text);
	free(cmd->cmdBuf);
}

/* remove a job from the jobList */
static void removeJob(struct jobSet *jobList, struct job *job)
{
	struct job *prevJob;

	freeJob(job);
	if (job == jobList->head) {
		jobList->head = job->next;
	} else {
		prevJob = jobList->head;
		while (prevJob->next != job)
			prevJob = prevJob->next;
		prevJob->next = job->next;
	}

	free(job);
}

/* Checks to see if any background processes have exited -- if they 
   have, figure out why and see if a job has completed */
static void checkJobs(struct jobSet *jobList)
{
	struct job *job;
	pid_t childpid;
	int status;
	int progNum = 0;

	while ((childpid = waitpid(-1, &status, WNOHANG | WUNTRACED)) > 0) {
		for (job = jobList->head; job; job = job->next) {
			progNum = 0;
			while (progNum < job->numProgs &&
				   job->progs[progNum].pid != childpid) progNum++;
			if (progNum < job->numProgs)
				break;
		}

		if (WIFEXITED(status) || WIFSIGNALED(status)) {
			/* child exited */
			job->runningProgs--;
			job->progs[progNum].pid = 0;

			if (!job->runningProgs) {
				printf(JOB_STATUS_FORMAT, job->jobId, "Done", job->text);
				removeJob(jobList, job);
			}
		} else {
			/* child stopped */
			job->stoppedProgs++;
			job->progs[progNum].isStopped = 1;

			if (job->stoppedProgs == job->numProgs) {
				printf(JOB_STATUS_FORMAT, job->jobId, "Stopped",
					   job->text);
			}
		}
	}

	if (childpid == -1 && errno != ECHILD)
		perror("waitpid");
}

static int getCommand(FILE * source, char *command)
{
	if (source == stdin) {
#ifdef BB_FEATURE_SH_COMMAND_EDITING
		int len;
		char *promptStr;
		len=fprintf(stdout, "%s %s", cwd, prompt);
		fflush(stdout);
		promptStr=(char*)malloc(sizeof(char)*(len+1));
		sprintf(promptStr, "%s %s", cwd, prompt);
		cmdedit_read_input(promptStr, command);
		free( promptStr);
		return 0;
#else
		fprintf(stdout, "%s %s", cwd, prompt);
		fflush(stdout);
#endif
	}

	if (!fgets(command, BUFSIZ - 2, source)) {
		if (source == stdin)
			printf("\n");
		return 1;
	}

	/* remove trailing newline */
	command[strlen(command) - 1] = '\0';

	return 0;
}

static void globLastArgument(struct childProgram *prog, int *argcPtr,
							 int *argcAllocedPtr)
{
	int argc = *argcPtr;
	int argcAlloced = *argcAllocedPtr;
	int rc;
	int flags;
	int i;
	char *src, *dst;

	if (argc > 1) {				/* cmd->globResult is already initialized */
		flags = GLOB_APPEND;
		i = prog->globResult.gl_pathc;
	} else {
		prog->freeGlob = 1;
		flags = 0;
		i = 0;
	}

	rc = glob(prog->argv[argc - 1], flags, NULL, &prog->globResult);
	if (rc == GLOB_NOSPACE) {
		fprintf(stderr, "out of space during glob operation\n");
		return;
	} else if (rc == GLOB_NOMATCH ||
			   (!rc && (prog->globResult.gl_pathc - i) == 1 &&
				!strcmp(prog->argv[argc - 1],
						prog->globResult.gl_pathv[i]))) {
		/* we need to remove whatever \ quoting is still present */
		src = dst = prog->argv[argc - 1];
		while (*src) {
			if (*src != '\\')
				*dst++ = *src;
			src++;
		}
		*dst = '\0';
	} else if (!rc) {
		argcAlloced += (prog->globResult.gl_pathc - i);
		prog->argv =
			realloc(prog->argv, argcAlloced * sizeof(*prog->argv));
		memcpy(prog->argv + (argc - 1), prog->globResult.gl_pathv + i,
			   sizeof(*(prog->argv)) * (prog->globResult.gl_pathc - i));
		argc += (prog->globResult.gl_pathc - i - 1);
	}

	*argcAllocedPtr = argcAlloced;
	*argcPtr = argc;
}

/* Return cmd->numProgs as 0 if no command is present (e.g. an empty
   line). If a valid command is found, commandPtr is set to point to
   the beginning of the next command (if the original command had more 
   then one job associated with it) or NULL if no more commands are 
   present. */
static int parseCommand(char **commandPtr, struct job *job, int *isBg)
{
	char *command;
	char *returnCommand = NULL;
	char *src, *buf, *chptr;
	int argc = 0;
	int done = 0;
	int argvAlloced;
	int i;
	char quote = '\0';
	int count;
	struct childProgram *prog;

	/* skip leading white space */
	while (**commandPtr && isspace(**commandPtr))
		(*commandPtr)++;

	/* this handles empty lines or leading '#' characters */
	if (!**commandPtr || (**commandPtr == '#')) {
		job->numProgs = 0;
		*commandPtr = NULL;
		return 0;
	}

	*isBg = 0;
	job->numProgs = 1;
	job->progs = malloc(sizeof(*job->progs));

	/* We set the argv elements to point inside of this string. The 
	   memory is freed by freeJob(). 

	   Getting clean memory relieves us of the task of NULL 
	   terminating things and makes the rest of this look a bit 
	   cleaner (though it is, admittedly, a tad less efficient) */
	job->cmdBuf = command = calloc(1, strlen(*commandPtr) + 1);
	job->text = NULL;

	prog = job->progs;
	prog->numRedirections = 0;
	prog->redirections = NULL;
	prog->freeGlob = 0;
	prog->isStopped = 0;

	argvAlloced = 5;
	prog->argv = malloc(sizeof(*prog->argv) * argvAlloced);
	prog->argv[0] = job->cmdBuf;

	buf = command;
	src = *commandPtr;
	while (*src && !done) {
		if (quote == *src) {
			quote = '\0';
		} else if (quote) {
			if (*src == '\\') {
				src++;
				if (!*src) {
					fprintf(stderr, "character expected after \\\n");
					freeJob(job);
					return 1;
				}

				/* in shell, "\'" should yield \' */
				if (*src != quote)
					*buf++ = '\\';
			} else if (*src == '*' || *src == '?' || *src == '[' ||
					   *src == ']') *buf++ = '\\';
			*buf++ = *src;
		} else if (isspace(*src)) {
			if (*prog->argv[argc]) {
				buf++, argc++;
				/* +1 here leaves room for the NULL which ends argv */
				if ((argc + 1) == argvAlloced) {
					argvAlloced += 5;
					prog->argv = realloc(prog->argv,
										 sizeof(*prog->argv) *
										 argvAlloced);
				}
				prog->argv[argc] = buf;

				globLastArgument(prog, &argc, &argvAlloced);
			}
		} else
			switch (*src) {
			case '"':
			case '\'':
				quote = *src;
				break;

			case '#':			/* comment */
				done = 1;
				break;

			case '>':			/* redirections */
			case '<':
				i = prog->numRedirections++;
				prog->redirections = realloc(prog->redirections,
											 sizeof(*prog->redirections) *
											 (i + 1));

				prog->redirections[i].fd = -1;
				if (buf != prog->argv[argc]) {
					/* the stuff before this character may be the file number 
					   being redirected */
					prog->redirections[i].fd =
						strtol(prog->argv[argc], &chptr, 10);

					if (*chptr && *prog->argv[argc]) {
						buf++, argc++;
						globLastArgument(prog, &argc, &argvAlloced);
					}
				}

				if (prog->redirections[i].fd == -1) {
					if (*src == '>')
						prog->redirections[i].fd = 1;
					else
						prog->redirections[i].fd = 0;
				}

				if (*src++ == '>') {
					if (*src == '>')
						prog->redirections[i].type =
							REDIRECT_APPEND, src++;
					else
						prog->redirections[i].type = REDIRECT_OVERWRITE;
				} else {
					prog->redirections[i].type = REDIRECT_INPUT;
				}

				/* This isn't POSIX sh compliant. Oh well. */
				chptr = src;
				while (isspace(*chptr))
					chptr++;

				if (!*chptr) {
					fprintf(stderr, "file name expected after %c\n", *src);
					freeJob(job);
					return 1;
				}

				prog->redirections[i].filename = buf;
				while (*chptr && !isspace(*chptr))
					*buf++ = *chptr++;

				src = chptr - 1;	/* we src++ later */
				prog->argv[argc] = ++buf;
				break;

			case '|':			/* pipe */
				/* finish this command */
				if (*prog->argv[argc])
					argc++;
				if (!argc) {
					fprintf(stderr, "empty command in pipe\n");
					freeJob(job);
					return 1;
				}
				prog->argv[argc] = NULL;

				/* and start the next */
				job->numProgs++;
				job->progs = realloc(job->progs,
									 sizeof(*job->progs) * job->numProgs);
				prog = job->progs + (job->numProgs - 1);
				prog->numRedirections = 0;
				prog->redirections = NULL;
				prog->freeGlob = 0;
				argc = 0;

				argvAlloced = 5;
				prog->argv = malloc(sizeof(*prog->argv) * argvAlloced);
				prog->argv[0] = ++buf;

				src++;
				while (*src && isspace(*src))
					src++;

				if (!*src) {
					fprintf(stderr, "empty command in pipe\n");
					return 1;
				}
				src--;			/* we'll ++ it at the end of the loop */

				break;

			case '&':			/* background */
				*isBg = 1;
			case ';':			/* multiple commands */
				done = 1;
				returnCommand = *commandPtr + (src - *commandPtr) + 1;
				break;

			case '\\':
				src++;
				if (!*src) {
					freeJob(job);
					fprintf(stderr, "character expected after \\\n");
					return 1;
				}
				if (*src == '*' || *src == '[' || *src == ']'
					|| *src == '?') *buf++ = '\\';
				/* fallthrough */
			default:
				*buf++ = *src;
			}

		src++;
	}

	if (*prog->argv[argc]) {
		argc++;
		globLastArgument(prog, &argc, &argvAlloced);
	}
	if (!argc) {
		freeJob(job);
		return 0;
	}
	prog->argv[argc] = NULL;

	if (!returnCommand) {
		job->text = malloc(strlen(*commandPtr) + 1);
		strcpy(job->text, *commandPtr);
	} else {
		/* This leaves any trailing spaces, which is a bit sloppy */
		count = returnCommand - *commandPtr;
		job->text = malloc(count + 1);
		strncpy(job->text, *commandPtr, count);
		job->text[count] = '\0';
	}

	*commandPtr = returnCommand;

	return 0;
}

static int runCommand(struct job newJob, struct jobSet *jobList, int inBg)
{
	struct job *job;
	int i;
	int nextin, nextout;
	int pipefds[2];				/* pipefd[0] is for reading */
	struct builtInCommand *x;

	/* handle built-ins here -- we don't fork() so we can't background
	   these very easily */
	for (x = bltins; x->cmd; x++) {
		if (!strcmp(newJob.progs[0].argv[0], x->cmd)) {
			return (x->function(&newJob, jobList));
		}
	}

	nextin = 0, nextout = 1;
	for (i = 0; i < newJob.numProgs; i++) {
		if ((i + 1) < newJob.numProgs) {
			pipe(pipefds);
			nextout = pipefds[1];
		} else {
			nextout = 1;
		}

		if (!(newJob.progs[i].pid = fork())) {
			signal(SIGTTOU, SIG_DFL);

			if (nextin != 0) {
				dup2(nextin, 0);
				close(nextin);
			}

			if (nextout != 1) {
				dup2(nextout, 1);
				close(nextout);
			}

			/* explicit redirections override pipes */
			setupRedirections(newJob.progs + i);

			execvp(newJob.progs[i].argv[0], newJob.progs[i].argv);
			fatalError("sh: %s: %s\n", newJob.progs[i].argv[0],
					   strerror(errno));
		}

		/* put our child in the process group whose leader is the
		   first process in this pipe */
		setpgid(newJob.progs[i].pid, newJob.progs[0].pid);

		if (nextin != 0)
			close(nextin);
		if (nextout != 1)
			close(nextout);

		/* If there isn't another process, nextin is garbage 
		   but it doesn't matter */
		nextin = pipefds[0];
	}

	newJob.pgrp = newJob.progs[0].pid;

	/* find the ID for the job to use */
	newJob.jobId = 1;
	for (job = jobList->head; job; job = job->next)
		if (job->jobId >= newJob.jobId)
			newJob.jobId = job->jobId + 1;

	/* add the job to the list of running jobs */
	if (!jobList->head) {
		job = jobList->head = malloc(sizeof(*job));
	} else {
		for (job = jobList->head; job->next; job = job->next);
		job->next = malloc(sizeof(*job));
		job = job->next;
	}

	*job = newJob;
	job->next = NULL;
	job->runningProgs = job->numProgs;
	job->stoppedProgs = 0;

	if (inBg) {
		/* we don't wait for background jobs to return -- append it 
		   to the list of backgrounded jobs and leave it alone */
		printf("[%d] %d\n", job->jobId,
			   newJob.progs[newJob.numProgs - 1].pid);
	} else {
		jobList->fg = job;

		/* move the new process group into the foreground */
		if (tcsetpgrp(0, newJob.pgrp))
			perror("tcsetpgrp");
	}

	return 0;
}

static int setupRedirections(struct childProgram *prog)
{
	int i;
	int openfd;
	int mode = O_RDONLY;
	struct redirectionSpecifier *redir = prog->redirections;

	for (i = 0; i < prog->numRedirections; i++, redir++) {
		switch (redir->type) {
		case REDIRECT_INPUT:
			mode = O_RDONLY;
			break;
		case REDIRECT_OVERWRITE:
			mode = O_RDWR | O_CREAT | O_TRUNC;
			break;
		case REDIRECT_APPEND:
			mode = O_RDWR | O_CREAT | O_APPEND;
			break;
		}

		openfd = open(redir->filename, mode, 0666);
		if (openfd < 0) {
			/* this could get lost if stderr has been redirected, but
			   bash and ash both lose it as well (though zsh doesn't!) */
			fprintf(stderr, "error opening %s: %s\n", redir->filename,
					strerror(errno));
			return 1;
		}

		if (openfd != redir->fd) {
			dup2(openfd, redir->fd);
			close(openfd);
		}
	}

	return 0;
}


static int busy_loop(FILE * input)
{
	char *command;
	char *nextCommand = NULL;
	struct jobSet jobList = { NULL, NULL };
	struct job newJob;
	int i;
	int status;
	int inBg;

	command = (char *) calloc(BUFSIZ, sizeof(char));

	/* don't pay any attention to this signal; it just confuses 
	   things and isn't really meant for shells anyway */
	signal(SIGTTOU, SIG_IGN);

	while (1) {
		if (!jobList.fg) {
			/* no job is in the foreground */

			/* see if any background processes have exited */
			checkJobs(&jobList);

			if (!nextCommand) {
				if (getCommand(input, command))
					break;
				nextCommand = command;
			}

			if (!parseCommand(&nextCommand, &newJob, &inBg) &&
				newJob.numProgs) {
				runCommand(newJob, &jobList, inBg);
			}
		} else {
			/* a job is running in the foreground; wait for it */
			i = 0;
			while (!jobList.fg->progs[i].pid ||
				   jobList.fg->progs[i].isStopped) i++;

			waitpid(jobList.fg->progs[i].pid, &status, WUNTRACED);

			if (WIFEXITED(status) || WIFSIGNALED(status)) {
				/* the child exited */
				jobList.fg->runningProgs--;
				jobList.fg->progs[i].pid = 0;

				if (!jobList.fg->runningProgs) {
					/* child exited */

					removeJob(&jobList, jobList.fg);
					jobList.fg = NULL;

					/* move the shell to the foreground */
					if (tcsetpgrp(0, getpid()))
						perror("tcsetpgrp");
				}
			} else {
				/* the child was stopped */
				jobList.fg->stoppedProgs++;
				jobList.fg->progs[i].isStopped = 1;

				if (jobList.fg->stoppedProgs == jobList.fg->runningProgs) {
					printf("\n" JOB_STATUS_FORMAT, jobList.fg->jobId,
						   "Stopped", jobList.fg->text);
					jobList.fg = NULL;
				}
			}

			if (!jobList.fg) {
				/* move the shell to the foreground */
				if (tcsetpgrp(0, getpid()))
					perror("tcsetpgrp");
			}
		}
	}
	free(command);

	return 0;
}


int shell_main(int argc, char **argv)
{
	FILE *input = stdin;

	if (argc > 2) {
		usage(shell_usage);
	}
	/* initialize the cwd */
	getcwd(cwd, sizeof(cwd));

#ifdef BB_FEATURE_SH_COMMAND_EDITING
	cmdedit_init();
	signal(SIGWINCH, win_changed);
	win_changed(0);
#endif

	//if (argv[0] && argv[0][0] == '-') {
	//      shell_source("/etc/profile");
	//}

	if (argc < 2) {
		fprintf(stdout, "\n\nBusyBox v%s (%s) Built-in shell\n", BB_VER, BB_BT);
		fprintf(stdout, "Enter 'help' for a list of built-in commands.\n\n");
	} else {
		if (*argv[1]=='-') {
			usage("sh\n\nlash -- the BusyBox LAme SHell (command interpreter)\n");
		}
		input = fopen(argv[1], "r");
		if (!input) {
			fatalError("sh: Couldn't open file '%s': %s\n", argv[1],
					   strerror(errno));
		}
	}

	return (busy_loop(input));
}