parser.c

操作系统源代码

/*-
 * Copyright (c) 1991 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kenneth Almquist.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static char sccsid[] = "@(#)parser.c	5.3 (Berkeley) 4/12/91";
#endif /* not lint */

#include "shell.h"
#include "parser.h"
#include "nodes.h"
#include "expand.h"	/* defines rmescapes() */
#include "redir.h"	/* defines copyfd() */
#include "syntax.h"
#include "options.h"
#include "input.h"
#include "output.h"
#include "var.h"
#include "error.h"
#include "memalloc.h"
#include "mystring.h"


/*
 * Shell command parser.
 */

#define EOFMARKLEN 79

/* values returned by readtoken */
#include "token.def"



struct heredoc {
	struct heredoc *next;	/* next here document in list */
	union node *here;		/* redirection node */
	char *eofmark;		/* string indicating end of input */
	int striptabs;		/* if set, strip leading tabs */
};



struct heredoc *heredoclist;	/* list of here documents to read */
int parsebackquote;		/* nonzero if we are inside backquotes */
int doprompt;			/* if set, prompt the user */
int needprompt;			/* true if interactive and at start of line */
int lasttoken;			/* last token read */
MKINIT int tokpushback;		/* last token pushed back */
char *wordtext;			/* text of last word returned by readtoken */
int checkkwd;               /* 1 == check for kwds, 2 == also eat newlines */
struct nodelist *backquotelist;
union node *redirnode;
struct heredoc *heredoc;
int quoteflag;			/* set if (part of) last token was quoted */
int startlinno;			/* line # where last token started */


#define GDB_HACK 1 /* avoid local declarations which gdb can't handle */
#ifdef GDB_HACK
static const char argvars[5] = {CTLVAR, VSNORMAL|VSQUOTE, '@', '=', '\0'};
static const char types[] = "}-+?=";
#endif


STATIC union node *list __P((int));
STATIC union node *andor __P((void));
STATIC union node *pipeline __P((void));
STATIC union node *command __P((void));
STATIC union node *simplecmd __P((union node **, union node *));
STATIC void parsefname __P((void));
STATIC void parseheredoc __P((void));
STATIC int readtoken __P((void));
STATIC int readtoken1 __P((int, char const *, char *, int));
STATIC void attyline __P((void));
STATIC int noexpand __P((char *));
STATIC void synexpect __P((int));
STATIC void synerror __P((char *));

#if ATTY || READLINE
STATIC void putprompt __P((char *));
#else /* not ATTY */
#define putprompt(s)	out2str(s)
#endif




/*
 * Read and parse a command.  Returns NEOF on end of file.  (NULL is a
 * valid parse tree indicating a blank line.)
 */

union node *
parsecmd(interact) {
	int t;
	extern int exitstatus;

	doprompt = interact;
	if (doprompt)
		putprompt(exitstatus == 0 || vpse.flags & VUNSET
					? ps1val() : pseval());
	needprompt = 0;
	if ((t = readtoken()) == TEOF)
		return NEOF;
	if (t == TNL)
		return NULL;
	tokpushback++;
	return list(1);
}


STATIC union node *
list(nlflag) {
	union node *n1, *n2, *n3, **pn;
	int first;

	checkkwd = 2;
	if (nlflag == 0 && tokendlist[peektoken()])
		return NULL;
	n1 = andor();
	for (first = 1; ; first = 0) {
		switch (readtoken()) {
		case TBACKGND:
			pn = &n1;
			if (!first && n1->type == NSEMI) pn = &n1->nbinary.ch2;
			if ((*pn)->type == NCMD || (*pn)->type == NPIPE) {
				(*pn)->ncmd.backgnd = 1;
			} else if ((*pn)->type == NREDIR) {
				(*pn)->type = NBACKGND;
			} else {
				n3 = (union node *)stalloc(sizeof (struct nredir));
				n3->type = NBACKGND;
				n3->nredir.n = *pn;
				n3->nredir.redirect = NULL;
				*pn = n3;
			}
			goto tsemi;
		case TNL:
			tokpushback++;
			/* fall through */
tsemi:		case TSEMI:
			if (readtoken() == TNL) {
				parseheredoc();
				if (nlflag)
					return n1;
			} else {
				tokpushback++;
			}
			checkkwd = 2;
			if (tokendlist[peektoken()])
				return n1;
			n2 = andor();
			n3 = (union node *)stalloc(sizeof (struct nbinary));
			n3->type = NSEMI;
			n3->nbinary.ch1 = n1;
			n3->nbinary.ch2 = n2;
			n1 = n3;
			break;
		case TEOF:
			if (heredoclist)
				parseheredoc();
			else
				pungetc();		/* push back EOF on input */
			return n1;
		default:
			if (nlflag)
				synexpect(-1);
			tokpushback++;
			return n1;
		}
	}
}



STATIC union node *
andor() {
	union node *n1, *n2, *n3;
	int t;

	n1 = pipeline();
	for (;;) {
		if ((t = readtoken()) == TAND) {
			t = NAND;
		} else if (t == TOR) {
			t = NOR;
		} else {
			tokpushback++;
			return n1;
		}
		n2 = pipeline();
		n3 = (union node *)stalloc(sizeof (struct nbinary));
		n3->type = t;
		n3->nbinary.ch1 = n1;
		n3->nbinary.ch2 = n2;
		n1 = n3;
	}
}



STATIC union node *
pipeline() {
	union node *n1, *pipenode;
	struct nodelist *lp, *prev;

	n1 = command();
	if (readtoken() == TPIPE) {
		pipenode = (union node *)stalloc(sizeof (struct npipe));
		pipenode->type = NPIPE;
		pipenode->npipe.backgnd = 0;
		lp = (struct nodelist *)stalloc(sizeof (struct nodelist));
		pipenode->npipe.cmdlist = lp;
		lp->n = n1;
		do {
			prev = lp;
			lp = (struct nodelist *)stalloc(sizeof (struct nodelist));
			lp->n = command();
			prev->next = lp;
		} while (readtoken() == TPIPE);
		lp->next = NULL;
		n1 = pipenode;
	}
	tokpushback++;
	return n1;
}



STATIC union node *
command() {
	union node *n1, *n2;
	union node *ap, **app;
	union node *cp, **cpp;
	union node *redir, **rpp;
	int t;

	checkkwd = 2;
	redir = 0;
	rpp = &redir;
	/* Check for redirection which may precede command */
	while (readtoken() == TREDIR) {
		*rpp = n2 = redirnode;
		rpp = &n2->nfile.next;
		parsefname();
	}
	tokpushback++;

	switch (readtoken()) {
	case TIF:
		n1 = (union node *)stalloc(sizeof (struct nif));
		n1->type = NIF;
		n1->nif.test = list(0);
		if (readtoken() != TTHEN)
			synexpect(TTHEN);
		n1->nif.ifpart = list(0);
		n2 = n1;
		while (readtoken() == TELIF) {
			n2->nif.elsepart = (union node *)stalloc(sizeof (struct nif));
			n2 = n2->nif.elsepart;
			n2->type = NIF;
			n2->nif.test = list(0);
			if (readtoken() != TTHEN)
				synexpect(TTHEN);
			n2->nif.ifpart = list(0);
		}
		if (lasttoken == TELSE)
			n2->nif.elsepart = list(0);
		else {
			n2->nif.elsepart = NULL;
			tokpushback++;
		}
		if (readtoken() != TFI)
			synexpect(TFI);
		checkkwd = 1;
		break;
	case TWHILE:
	case TUNTIL: {
		int got;
		n1 = (union node *)stalloc(sizeof (struct nbinary));
		n1->type = (lasttoken == TWHILE)? NWHILE : NUNTIL;
		n1->nbinary.ch1 = list(0);
		if ((got=readtoken()) != TDO) {
TRACE(("expecting DO got %s %s\n", tokname[got], got == TWORD ? wordtext : ""));
			synexpect(TDO);
		}
		n1->nbinary.ch2 = list(0);
		if (readtoken() != TDONE)
			synexpect(TDONE);
		checkkwd = 1;
		break;
	}
	case TFOR:
		if (readtoken() != TWORD || quoteflag || ! goodname(wordtext))
			synerror("Bad for loop variable");
		n1 = (union node *)stalloc(sizeof (struct nfor));
		n1->type = NFOR;
		n1->nfor.var = wordtext;
		if (readtoken() == TWORD && ! quoteflag && equal(wordtext, "in")) {
			app = ≈
			while (readtoken() == TWORD) {
				n2 = (union node *)stalloc(sizeof (struct narg));
				n2->type = NARG;
				n2->narg.text = wordtext;
				n2->narg.backquote = backquotelist;
				*app = n2;
				app = &n2->narg.next;
			}
			*app = NULL;
			n1->nfor.args = ap;
			/* A newline or semicolon is required here to end
			   the list.  */
			if (lasttoken != TNL && lasttoken != TSEMI)
				synexpect(-1);
		} else {
#ifndef GDB_HACK
			static const char argvars[5] = {CTLVAR, VSNORMAL|VSQUOTE,
								   '@', '=', '\0'};
#endif
			n2 = (union node *)stalloc(sizeof (struct narg));
			n2->type = NARG;
			n2->narg.text = (char *)argvars;
			n2->narg.backquote = NULL;
			n2->narg.next = NULL;
			n1->nfor.args = n2;
			/* A newline or semicolon is optional here. Anything
			   else gets pushed back so we can read it again.  */
			if (lasttoken != TNL && lasttoken != TSEMI)
				tokpushback++;
		}
		checkkwd = 2;
		if ((t = readtoken()) == TDO)
			t = TDONE;
		else if (t == TBEGIN)
			t = TEND;
		else
			synexpect(-1);
		n1->nfor.body = list(0);
		if (readtoken() != t)
			synexpect(t);
		checkkwd = 1;
		break;
	case TCASE:
		n1 = (union node *)stalloc(sizeof (struct ncase));
		n1->type = NCASE;
		if (readtoken() != TWORD)
			synexpect(TWORD);
		n1->ncase.expr = n2 = (union node *)stalloc(sizeof (struct narg));
		n2->type = NARG;
		n2->narg.text = wordtext;
		n2->narg.backquote = backquotelist;
		n2->narg.next = NULL;
		while (readtoken() == TNL);
		if (lasttoken != TWORD || ! equal(wordtext, "in"))
			synerror("expecting \"in\"");
		cpp = &n1->ncase.cases;
		while (checkkwd = 2, readtoken() == TWORD) {
			*cpp = cp = (union node *)stalloc(sizeof (struct nclist));
			cp->type = NCLIST;
			app = &cp->nclist.pattern;
			for (;;) {
				*app = ap = (union node *)stalloc(sizeof (struct narg));
				ap->type = NARG;
				ap->narg.text = wordtext;
				ap->narg.backquote = backquotelist;
				if (readtoken() != TPIPE)
					break;
				app = &ap->narg.next;
				if (readtoken() != TWORD)
					synexpect(TWORD);
			}
			ap->narg.next = NULL;
			if (lasttoken != TRP)
				synexpect(TRP);
			cp->nclist.body = list(0);
			if ((t = readtoken()) == TESAC)
				tokpushback++;
			else if (t != TENDCASE)
				synexpect(TENDCASE);
			cpp = &cp->nclist.next;
		}
		*cpp = NULL;
		if (lasttoken != TESAC)
			synexpect(TESAC);
		checkkwd = 1;
		break;
	case TLP:
		n1 = (union node *)stalloc(sizeof (struct nredir));
		n1->type = NSUBSHELL;
		n1->nredir.n = list(0);
		n1->nredir.redirect = NULL;
		if (readtoken() != TRP)
			synexpect(TRP);
		checkkwd = 1;
		break;
	case TBEGIN:
		n1 = list(0);
		if (readtoken() != TEND)
			synexpect(TEND);
		checkkwd = 1;
		break;
	/* Handle an empty command like other simple commands.  */
	case TNL:
	case TSEMI:
	case TEND:
	case TRP:
	case TEOF:
	case TWORD:
		tokpushback++;
		return simplecmd(rpp, redir);
	default:
		synexpect(-1);
	}

	/* Now check for redirection which may follow command */
	while (readtoken() == TREDIR) {
		*rpp = n2 = redirnode;
		rpp = &n2->nfile.next;
		parsefname();
	}
	tokpushback++;
	*rpp = NULL;
	if (redir) {
		if (n1->type != NSUBSHELL) {
			n2 = (union node *)stalloc(sizeof (struct nredir));
			n2->type = NREDIR;
			n2->nredir.n = n1;
			n1 = n2;
		}
		n1->nredir.redirect = redir;
	}
	return n1;
}


STATIC union node *
simplecmd(rpp, redir)
	union node **rpp, *redir;
	{
	union node *args, **app;
	union node **orig_rpp = rpp;
	union node *n;

	/* If we don't have any redirections already, then we must reset
	   rpp to be the address of the local redir variable.  */
	if (redir == 0)
		rpp = &redir;

	args = NULL;
	app = &args;
	/* We save the incoming value, because we need this for shell
	   functions.  There can not be a redirect or an argument between
	   the function name and the open parenthesis.  */
	orig_rpp = rpp;
	for (;;) {
		if (readtoken() == TWORD) {
			n = (union node *)stalloc(sizeof (struct narg));
			n->type = NARG;
			n->narg.text = wordtext;
			n->narg.backquote = backquotelist;
			*app = n;
			app = &n->narg.next;
		} else if (lasttoken == TREDIR) {
			*rpp = n = redirnode;
			rpp = &n->nfile.next;
			parsefname();	/* read name of redirection file */
		} else if (lasttoken == TLP && app == &args->narg.next
					    && rpp == orig_rpp) {
			/* We have a function */
			if (readtoken() != TRP)
				synexpect(TRP);
#ifdef notdef
			if (! goodname(n->narg.text))
				synerror("Bad function name");
#endif
			n->type = NDEFUN;
			n->narg.next = command();
			return n;
		} else {
			tokpushback++;
			break;
		}
	}
	*app = NULL;
	*rpp = NULL;
	n = (union node *)stalloc(sizeof (struct ncmd));
	n->type = NCMD;
	n->ncmd.backgnd = 0;
	n->ncmd.args = args;
	n->ncmd.redirect = redir;
	return n;
}


STATIC void
parsefname() {
	union node *n = redirnode;

	if (readtoken() != TWORD)
		synexpect(-1);
	if (n->type == NHERE) {
		struct heredoc *here = heredoc;
		struct heredoc *p;
		int i;

		if (quoteflag == 0)
			n->type = NXHERE;
		TRACE(("Here document %d\n", n->type));
		if (here->striptabs) {
			while (*wordtext == '\t')
				wordtext++;
		}
		if (! noexpand(wordtext) || (i = strlen(wordtext)) == 0 || i > EOFMARKLEN)
			synerror("Illegal eof marker for << redirection");
		rmescapes(wordtext);
		here->eofmark = wordtext;
		here->next = NULL;
		if (heredoclist == NULL)
			heredoclist = here;
		else {
			for (p = heredoclist ; p->next ; p = p->next);
			p->next = here;
		}
	} else if (n->type == NTOFD || n->type == NFROMFD) {
		if (is_digit(wordtext[0]))
			n->ndup.dupfd = digit_val(wordtext[0]);
		else if (wordtext[0] == '-')
			n->ndup.dupfd = -1;
		else
			goto bad;
		if (wordtext[1] != '\0') {
bad:
			synerror("Bad fd number");
		}
	} else {
		n->nfile.fname = (union node *)stalloc(sizeof (struct narg));
		n = n->nfile.fname;
		n->type = NARG;
		n->narg.next = NULL;
		n->narg.text = wordtext;
		n->narg.backquote = backquotelist;
	}
}


/*
 * Input any here documents.
 */

STATIC void
parseheredoc() {
	struct heredoc *here;
	union node *n;

	while (heredoclist) {
		here = heredoclist;
		heredoclist = here->next;
		if (needprompt) {
			putprompt(ps2val());
			needprompt = 0;
		}
		readtoken1(pgetc(), here->here->type == NHERE? SQSYNTAX : DQSYNTAX,
				here->eofmark, here->striptabs);
		n = (union node *)stalloc(sizeof (struct narg));
		n->narg.type = NARG;
		n->narg.next = NULL;
		n->narg.text = wordtext;
		n->narg.backquote = backquotelist;
		here->here->nhere.doc = n;
	}
}

STATIC int
peektoken() {
	int t;

	t = readtoken();
	tokpushback++;
	return (t);
}

STATIC int xxreadtoken();

STATIC int
readtoken() {
	int t;
#if DEBUG
	int alreadyseen = tokpushback;
#endif
	
	t = xxreadtoken();

	if (checkkwd) {
		/*
		 * eat newlines
		 */
		if (checkkwd == 2) {
			checkkwd = 0;
			while (t == TNL) {
				parseheredoc();
				t = xxreadtoken();
			}
		} else
			checkkwd = 0;
		/*
		 * check for keywords
		 */
		if (t == TWORD && !quoteflag) {
			register char *const *pp;

			for (pp = parsekwd; *pp; pp++) {
				if (**pp == *wordtext && equal(*pp, wordtext)) {
					lasttoken = t = pp - parsekwd + KWDOFFSET;
					TRACE(("keyword %s recognized\n", tokname[t]));
					break;
				}
			}
		}
	}
#if DEBUG
	if (!alreadyseen)
	    TRACE(("token %s %s\n", tokname[t], t == TWORD ? wordtext : ""));
	else
	    TRACE(("reread token %s %s\n", tokname[t], t == TWORD ? wordtext : ""));
#endif
	return (t);
}


/*
 * Read the next input token.
 * If the token is a word, we set backquotelist to the list of cmds in
 *	backquotes.  We set quoteflag to true if any part of the word was