main.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

/*
 * startup, main loop, enviroments and error handling
 */

#define	EXTERN				/* define EXTERNs in sh.h */

#include "sh.h"
#include "ksh_stat.h"
#include "ksh_time.h"

extern char **environ;

/*
 * global data
 */

static void	reclaim ARGS((void));
static void	remove_temps ARGS((struct temp *tp));
static int	is_restricted ARGS((char *name));

/*
 * shell initialization
 */

static const char initifs[] = "IFS= \t\n";

static const char initsubs[] = "${PS2=> } ${PS3=#? } ${PS4=+ }";

static const char version_param[] =
#ifdef KSH
	"KSH_VERSION"
#else /* KSH */
	"SH_VERSION"
#endif /* KSH */
	;

static const char *const initcoms [] = {
	"typeset", "-x", "SHELL", "PATH", "HOME", NULL,
	"typeset", "-r", version_param, NULL,
	"typeset", "-i", "PPID", NULL,
	"typeset", "-i", "OPTIND=1", NULL,
#ifdef KSH
	"eval", "typeset -i RANDOM MAILCHECK=\"${MAILCHECK-600}\" SECONDS=\"${SECONDS-0}\" TMOUT=\"${TMOUT-0}\"", NULL,
#endif /* KSH */
	"alias",
	 /* Standard ksh aliases */
	  "hash=alias -t",	/* not "alias -t --": hash -r needs to work */
	  "type=whence -v",
#ifdef JOBS
	  "stop=kill -STOP",
	  "suspend=kill -STOP $$",
#endif
#ifdef KSH
	  "autoload=typeset -fu",
	  "functions=typeset -f",
# ifdef HISTORY
	  "history=fc -l",
# endif /* HISTORY */
	  "integer=typeset -i",
	  "nohup=nohup ",
	  "local=typeset",
	  "r=fc -e -",
#endif /* KSH */
#ifdef KSH
	 /* Aliases that are builtin commands in at&t */
	  "login=exec login",
	  "newgrp=exec newgrp",
#endif /* KSH */
	  NULL,
	/* this is what at&t ksh seems to track, with the addition of emacs */
	"alias", "-tU",
	  "cat", "cc", "chmod", "cp", "date", "ed", "emacs", "grep", "ls",
	  "mail", "make", "mv", "pr", "rm", "sed", "sh", "vi", "who",
	  NULL,
#ifdef EXTRA_INITCOMS
	EXTRA_INITCOMS, NULL,
#endif /* EXTRA_INITCOMS */
	NULL
};

int
main(argc, argv)
	int argc;
	register char **argv;
{
	register int i;
	int argi;
	Source *s;
	struct block *l;
	int restricted, errexit;
	char **wp;
	struct env env;
	pid_t ppid;

#ifdef MEM_DEBUG
	chmem_set_defaults("ct", 1);
	/* chmem_push("+c", 1); */
#endif /* MEM_DEBUG */

#ifdef OS2
	setmode (0, O_BINARY);
	setmode (1, O_TEXT);
#endif

	/* make sure argv[] is sane */
	if (!*argv) {
		static const char	*empty_argv[] = {
					    "pdksh", (char *) 0
					};

		argv = (char **) empty_argv;
		argc = 1;
	}
	kshname = *argv;

	ainit(&aperm);		/* initialize permanent Area */

	/* set up base enviroment */
	memset(&env, 0, sizeof(env));
	env.type = E_NONE;
	ainit(&env.area);
	e = &env;
	newblock();		/* set up global l->vars and l->funs */

	/* Do this first so output routines (eg, errorf, shellf) can work */
	initio();

	initvar();

	initctypes();

	inittraps();

#ifdef KSH
	coproc_init();
#endif /* KSH */

	/* set up variable and command dictionaries */
	tinit(&taliases, APERM, 0);
	tinit(&aliases, APERM, 0);
	tinit(&homedirs, APERM, 0);

	/* define shell keywords */
	initkeywords();

	/* define built-in commands */
	tinit(&builtins, APERM, 64); /* must be 2^n (currently 40 builtins) */
	for (i = 0; shbuiltins[i].name != NULL; i++)
		builtin(shbuiltins[i].name, shbuiltins[i].func);
	for (i = 0; kshbuiltins[i].name != NULL; i++)
		builtin(kshbuiltins[i].name, kshbuiltins[i].func);

	init_histvec();

	def_path = DEFAULT__PATH;
#if defined(HAVE_CONFSTR) && defined(_CS_PATH)
	{
		size_t len = confstr(_CS_PATH, (char *) 0, 0);
		char *new;

		if (len > 0) {
			confstr(_CS_PATH, new = alloc(len + 1, APERM), len + 1);
			def_path = new;
		}
	}
#endif /* HAVE_CONFSTR && _CS_PATH */

	/* Set PATH to def_path (will set the path global variable).
	 * (import of environment below will probably change this setting).
	 */
	{
		struct tbl *vp = global("PATH");
		/* setstr can't fail here */
		setstr(vp, def_path, KSH_RETURN_ERROR);
	}


	/* Turn on nohup by default for how - will change to off
	 * by default once people are aware of its existance
	 * (at&t ksh does not have a nohup option - it always sends
	 * the hup).
	 */
	Flag(FNOHUP) = 1;

	/* Turn on brace expansion by default.  At&t ksh's that have
	 * alternation always have it on.  BUT, posix doesn't have
	 * brace expansion, so set this before setting up FPOSIX
	 * (change_flag() clears FBRACEEXPAND when FPOSIX is set).
	 */
#ifdef BRACE_EXPAND
	Flag(FBRACEEXPAND) = 1;
#endif /* BRACE_EXPAND */

	/* set posix flag just before environment so that it will have
	 * exactly the same effect as the POSIXLY_CORRECT environment
	 * variable.  If this needs to be done sooner to ensure correct posix
	 * operation, an initial scan of the environment will also have
	 * done sooner.
	 */
#ifdef POSIXLY_CORRECT
	change_flag(FPOSIX, OF_SPECIAL, 1);
#endif /* POSIXLY_CORRECT */

	/* import enviroment */
	if (environ != NULL)
		for (wp = environ; *wp != NULL; wp++)
			typeset(*wp, IMPORT|EXPORT, 0, 0, 0);

	kshpid = procpid = getpid();
	typeset(initifs, 0, 0, 0, 0);	/* for security */

	/* assign default shell variable values */
	substitute(initsubs, 0);

	/* Figure out the current working directory and set $PWD */
	{
		struct stat s_pwd, s_dot;
		struct tbl *pwd_v = global("PWD");
		char *pwd = str_val(pwd_v);
		char *pwdx = pwd;

		/* Try to use existing $PWD if it is valid */
		if (!ISABSPATH(pwd)
		    || stat(pwd, &s_pwd) < 0 || stat(".", &s_dot) < 0
		    || s_pwd.st_dev != s_dot.st_dev
		    || s_pwd.st_ino != s_dot.st_ino)
			pwdx = (char *) 0;
		set_current_wd(pwdx);
		if (current_wd[0])
			simplify_path(current_wd);
		/* Only set pwd if we know where we are or if it had a
		 * bogus value
		 */
		if (current_wd[0] || pwd != null)
			/* setstr can't fail here */
			setstr(pwd_v, current_wd, KSH_RETURN_ERROR);
	}
	ppid = getppid();
	setint(global("PPID"), (long) ppid);
#ifdef KSH
	setint(global("RANDOM"), (long) (time((time_t *)0) * kshpid * ppid));
#endif /* KSH */
	/* setstr can't fail here */
	setstr(global(version_param), ksh_version, KSH_RETURN_ERROR);

	/* execute initialization statements */
	for (wp = (char**) initcoms; *wp != NULL; wp++) {
		shcomexec(wp);
		for (; *wp != NULL; wp++)
			;
	}


	ksheuid = geteuid();
	safe_prompt = ksheuid ? "$ " : "# ";
	{
		struct tbl *vp = global("PS1");

		/* Set PS1 if it isn't set, or we are root and prompt doesn't
		 * contain a #.
		 */
		if (!(vp->flag & ISSET)
		    || (!ksheuid && !strchr(str_val(vp), '#')))
			/* setstr can't fail here */
			setstr(vp, safe_prompt, KSH_RETURN_ERROR);
	}

	/* Set this before parsing arguments */
	Flag(FPRIVILEGED) = getuid() != ksheuid || getgid() != getegid();

	/* this to note if monitor is set on command line (see below) */
	Flag(FMONITOR) = 127;
	argi = parse_args(argv, OF_CMDLINE, (int *) 0);
	if (argi < 0)
		exit(1);

	if (Flag(FCOMMAND)) {
		s = pushs(SSTRING, ATEMP);
		if (!(s->start = s->str = argv[argi++]))
			errorf("-c requires an argument");
		if (argv[argi])
			kshname = argv[argi++];
	} else if (argi < argc && !Flag(FSTDIN)) {
		s = pushs(SFILE, ATEMP);
#ifdef OS2
		/* a bug in os2 extproc shell processing doesn't
		 * pass full pathnames so we have to search for it.
		 * This changes the behavior of 'ksh arg' to search
		 * the users search path but it can't be helped.
		 */
		s->file = search(argv[argi++], path, R_OK, (int *) 0);
		if (!s->file || !*s->file)
		        s->file = argv[argi - 1];
#else
		s->file = argv[argi++];
#endif /* OS2 */
		s->u.shf = shf_open(s->file, O_RDONLY, 0, SHF_MAPHI|SHF_CLEXEC);
		if (s->u.shf == NULL) {
			exstat = 127; /* POSIX */
			errorf("%s: %s", s->file, strerror(errno));
		}
		kshname = s->file;
	} else {
		Flag(FSTDIN) = 1;
		s = pushs(SSTDIN, ATEMP);
		s->file = "<stdin>";
		s->u.shf = shf_fdopen(0, SHF_RD | can_seek(0),
				      (struct shf *) 0);
		if (!Flag(FNOTTALKING) && isatty(0) && isatty(2)) {
			Flag(FTALKING) = Flag(FTALKING_I) = 1;
			/* The following only if isatty(0) */
			s->flags |= SF_TTY;
			s->u.shf->flags |= SHF_INTERRUPT;
			s->file = (char *) 0;
		}
	}

	/* This bizarreness is mandated by POSIX */
	{
		struct stat s_stdin;

		if (fstat(0, &s_stdin) >= 0 && S_ISCHR(s_stdin.st_mode))
			reset_nonblock(0);
	}

	/* initialize job control */
	i = Flag(FMONITOR) != 127;
	Flag(FMONITOR) = 0;
	j_init(i);
#ifdef EDIT
	/* Do this after j_init(), as tty_fd is not initialized 'til then */
	if (Flag(FTALKING))
		x_init();
#endif

	l = e->loc;
	l->argv = &argv[argi - 1];
	l->argc = argc - argi;
	l->argv[0] = (char *) kshname;
	getopts_reset(1);

	/* Disable during .profile/ENV reading */
	restricted = Flag(FRESTRICTED);
	Flag(FRESTRICTED) = 0;
	errexit = Flag(FERREXIT);
	Flag(FERREXIT) = 0;

	/* Do this before profile/$ENV so that if it causes problems in them,
	 * user will know why things broke.
	 */
	if (!current_wd[0] && Flag(FTALKING))
		warningf(FALSE, "Cannot determine current working directory");

	if (Flag(FLOGIN)) {
#ifdef OS2
		char *profile;

		/* Try to find a profile - first see if $INIT has a value,
		 * then try /etc/profile.ksh, then c:/usr/etc/profile.ksh.
		 */
		if (!Flag(FPRIVILEGED)
		    && strcmp(profile = substitute("$INIT/profile.ksh", 0),
			      "/profile.ksh"))
			include(profile, 0, (char **) 0, 1);
		else if (include("/etc/profile.ksh", 0, (char **) 0, 1) < 0)
			include("c:/usr/etc/profile.ksh", 0, (char **) 0, 1);
		if (!Flag(FPRIVILEGED))
			include(substitute("$HOME/profile.ksh", 0), 0,
				(char **) 0, 1);
#else /* OS2 */
		include(KSH_SYSTEM_PROFILE, 0, (char **) 0, 1);
		if (!Flag(FPRIVILEGED))
			include(substitute("$HOME/.profile", 0), 0,
				(char **) 0, 1);
#endif /* OS2 */
	}

	if (Flag(FPRIVILEGED))
		include("/etc/suid_profile", 0, (char **) 0, 1);
	else {
		char *env_file;

#ifndef KSH
		if (!Flag(FPOSIX))
			env_file = null;
		else
#endif /* !KSH */
			/* include $ENV */
			env_file = str_val(global("ENV"));

#ifdef DEFAULT_ENV
		/* If env isn't set, include default environment */
		if (env_file == null)
			env_file = DEFAULT_ENV;
#endif /* DEFAULT_ENV */
		env_file = substitute(env_file, DOTILDE);
		if (*env_file != '\0')
			include(env_file, 0, (char **) 0, 1);
#ifdef OS2
		else if (Flag(FTALKING))
			include(substitute("$HOME/kshrc.ksh", 0), 0,
				(char **) 0, 1);
#endif /* OS2 */
	}

	if (is_restricted(argv[0]) || is_restricted(str_val(global("SHELL"))))
		restricted = 1;
	if (restricted) {
		static const char *const restr_com[] = {
						"typeset", "-r", "PATH",
						    "ENV", "SHELL",
						(char *) 0
					    };
		shcomexec((char **) restr_com);
		/* After typeset command... */
		Flag(FRESTRICTED) = 1;
	}
	if (errexit)
		Flag(FERREXIT) = 1;

	if (Flag(FTALKING)) {
		hist_init(s);
#ifdef KSH
		alarm_init();