expand.c

早期freebsd实现

/*-
 * Copyright (c) 1991, 1993
 *	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[] = "@(#)expand.c	8.2 (Berkeley) 10/22/93";
#endif /* not lint */

/*
 * Routines to expand arguments to commands.  We have to deal with
 * backquotes, shell variables, and file metacharacters.
 */

#include "shell.h"
#include "main.h"
#include "nodes.h"
#include "eval.h"
#include "expand.h"
#include "syntax.h"
#include "parser.h"
#include "jobs.h"
#include "options.h"
#include "var.h"
#include "input.h"
#include "output.h"
#include "memalloc.h"
#include "error.h"
#include "mystring.h"
#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <errno.h>
#include <dirent.h>
#include <pwd.h>

/*
 * Structure specifying which parts of the string should be searched
 * for IFS characters.
 */

struct ifsregion {
	struct ifsregion *next;	/* next region in list */
	int begoff;		/* offset of start of region */
	int endoff;		/* offset of end of region */
	int nulonly;		/* search for nul bytes only */
};


char *expdest;			/* output of current string */
struct nodelist *argbackq;	/* list of back quote expressions */
struct ifsregion ifsfirst;	/* first struct in list of ifs regions */
struct ifsregion *ifslastp;	/* last struct in list */
struct arglist exparg;		/* holds expanded arg list */

#ifdef __STDC__
STATIC void argstr(char *, int);
STATIC void expbackq(union node *, int, int);
STATIC char *evalvar(char *, int);
STATIC int varisset(int);
STATIC void varvalue(int, int, int);
STATIC void recordregion(int, int, int);
STATIC void ifsbreakup(char *, struct arglist *);
STATIC void expandmeta(struct strlist *, int);
STATIC void expmeta(char *, char *);
STATIC void expari(int);
STATIC void addfname(char *);
STATIC struct strlist *expsort(struct strlist *);
STATIC struct strlist *msort(struct strlist *, int);
STATIC int pmatch(char *, char *);
STATIC char *exptilde(char *, int);
#else
STATIC void argstr();
STATIC void expbackq();
STATIC char *evalvar();
STATIC int varisset();
STATIC void varvalue();
STATIC void recordregion();
STATIC void ifsbreakup();
STATIC void expandmeta();
STATIC void expmeta();
STATIC void expari();
STATIC void addfname();
STATIC struct strlist *expsort();
STATIC struct strlist *msort();
STATIC int pmatch();
STATIC char *exptilde();
#endif

/*
 * Expand shell variables and backquotes inside a here document.
 */

void
expandhere(arg, fd)
	union node *arg;	/* the document */
	int fd;			/* where to write the expanded version */
	{
	herefd = fd;
	expandarg(arg, (struct arglist *)NULL, 0);
	xwrite(fd, stackblock(), expdest - stackblock());
}


/*
 * Perform variable substitution and command substitution on an argument,
 * placing the resulting list of arguments in arglist.  If EXP_FULL is true,
 * perform splitting and file name expansion.  When arglist is NULL, perform
 * here document expansion.
 */

void
expandarg(arg, arglist, flag)
	union node *arg;
	struct arglist *arglist;
	{
	struct strlist *sp;
	char *p;

	argbackq = arg->narg.backquote;
	STARTSTACKSTR(expdest);
	ifsfirst.next = NULL;
	ifslastp = NULL;
	argstr(arg->narg.text, flag);
	if (arglist == NULL) {
		return;			/* here document expanded */
	}
	STPUTC('\0', expdest);
	p = grabstackstr(expdest);
	exparg.lastp = &exparg.list;
	/*
	 * TODO - EXP_REDIR
	 */
	if (flag & EXP_FULL) {
		ifsbreakup(p, &exparg);
		*exparg.lastp = NULL;
		exparg.lastp = &exparg.list;
		expandmeta(exparg.list, flag);
	} else {
		if (flag & EXP_REDIR) /*XXX - for now, just remove escapes */
			rmescapes(p);
		sp = (struct strlist *)stalloc(sizeof (struct strlist));
		sp->text = p;
		*exparg.lastp = sp;
		exparg.lastp = &sp->next;
	}
	while (ifsfirst.next != NULL) {
		struct ifsregion *ifsp;
		INTOFF;
		ifsp = ifsfirst.next->next;
		ckfree(ifsfirst.next);
		ifsfirst.next = ifsp;
		INTON;
	}
	*exparg.lastp = NULL;
	if (exparg.list) {
		*arglist->lastp = exparg.list;
		arglist->lastp = exparg.lastp;
	}
}



/*
 * Perform variable and command substitution.  If EXP_FULL is set, output CTLESC
 * characters to allow for further processing.  Otherwise treat
 * $@ like $* since no splitting will be performed.
 */

STATIC void
argstr(p, flag)
	register char *p;
	{
	register char c;
	int quotes = flag & (EXP_FULL | EXP_CASE);	/* do CTLESC */
	int firsteq = 1;

	if (*p == '~' && (flag & (EXP_TILDE | EXP_VARTILDE)))
		p = exptilde(p, flag);
	for (;;) {
		switch (c = *p++) {
		case '\0':
		case CTLENDVAR: /* ??? */
			goto breakloop;
		case CTLESC:
			if (quotes)
				STPUTC(c, expdest);
			c = *p++;
			STPUTC(c, expdest);
			break;
		case CTLVAR:
			p = evalvar(p, flag);
			break;
		case CTLBACKQ:
		case CTLBACKQ|CTLQUOTE:
			expbackq(argbackq->n, c & CTLQUOTE, flag);
			argbackq = argbackq->next;
			break;
		case CTLENDARI:
			expari(flag);
			break;
		case ':':
		case '=':
			/*
			 * sort of a hack - expand tildes in variable
			 * assignments (after the first '=' and after ':'s).
			 */
			STPUTC(c, expdest);
			if (flag & EXP_VARTILDE && *p == '~') {
				if (c == '=') {
					if (firsteq)
						firsteq = 0;
					else
						break;
				}
				p = exptilde(p, flag);
			}
			break;
		default:
			STPUTC(c, expdest);
		}
	}
breakloop:;
}

STATIC char *
exptilde(p, flag)
	char *p;
	{
	char c, *startp = p;
	struct passwd *pw;
	char *home;
	int quotes = flag & (EXP_FULL | EXP_CASE);

	while (c = *p) {
		switch(c) {
		case CTLESC:
			return (startp);
		case ':':
			if (flag & EXP_VARTILDE)
				goto done;
			break;
		case '/':
			goto done;
		}
		p++;
	}
done:
	*p = '\0';
	if (*(startp+1) == '\0') {
		if ((home = lookupvar("HOME")) == NULL)
			goto lose;
	} else {
		if ((pw = getpwnam(startp+1)) == NULL)
			goto lose;
		home = pw->pw_dir;
	}
	if (*home == '\0')
		goto lose;
	*p = c;
	while (c = *home++) {
		if (quotes && SQSYNTAX[c] == CCTL)
			STPUTC(CTLESC, expdest);
		STPUTC(c, expdest);
	}
	return (p);
lose:
	*p = c;
	return (startp);
}


/*
 * Expand arithmetic expression.  Backup to start of expression,
 * evaluate, place result in (backed up) result, adjust string position.
 */
void
expari(flag)
	{
	char *p, *start;
	int result;
	int quotes = flag & (EXP_FULL | EXP_CASE);

	/*
	 * This routine is slightly over-compilcated for
	 * efficiency.  First we make sure there is
	 * enough space for the result, which may be bigger
	 * than the expression if we add exponentation.  Next we
	 * scan backwards looking for the start of arithmetic.  If the
	 * next previous character is a CTLESC character, then we
	 * have to rescan starting from the beginning since CTLESC
	 * characters have to be processed left to right.  
	 */
	CHECKSTRSPACE(8, expdest);
	USTPUTC('\0', expdest); 
	start = stackblock();
	p = expdest;
	while (*p != CTLARI && p >= start)
		--p;
	if (*p != CTLARI)
		error("missing CTLARI (shouldn't happen)");
	if (p > start && *(p-1) == CTLESC)
		for (p = start; *p != CTLARI; p++)
			if (*p == CTLESC)
				p++;
	if (quotes)
		rmescapes(p+1);
	result = arith(p+1);
	fmtstr(p, 10, "%d", result);
	while (*p++)
		;
	result = expdest - p + 1;
	STADJUST(-result, expdest);
}


/*
 * Expand stuff in backwards quotes.
 */

STATIC void
expbackq(cmd, quoted, flag)
	union node *cmd;
	{
	struct backcmd in;
	int i;
	char buf[128];
	char *p;
	char *dest = expdest;
	struct ifsregion saveifs, *savelastp;
	struct nodelist *saveargbackq;
	char lastc;
	int startloc = dest - stackblock();
	char const *syntax = quoted? DQSYNTAX : BASESYNTAX;
	int saveherefd;
	int quotes = flag & (EXP_FULL | EXP_CASE);

	INTOFF;
	saveifs = ifsfirst;
	savelastp = ifslastp;
	saveargbackq = argbackq;
	saveherefd = herefd;      
	herefd = -1;
	p = grabstackstr(dest);
	evalbackcmd(cmd, &in);
	ungrabstackstr(p, dest);
	ifsfirst = saveifs;
	ifslastp = savelastp;
	argbackq = saveargbackq;
	herefd = saveherefd;

	p = in.buf;
	lastc = '\0';
	for (;;) {
		if (--in.nleft < 0) {
			if (in.fd < 0)
				break;
			while ((i = read(in.fd, buf, sizeof buf)) < 0 && errno == EINTR);
			TRACE(("expbackq: read returns %d\n", i));
			if (i <= 0)
				break;
			p = buf;
			in.nleft = i - 1;
		}
		lastc = *p++;
		if (lastc != '\0') {
			if (quotes && syntax[lastc] == CCTL)
				STPUTC(CTLESC, dest);
			STPUTC(lastc, dest);
		}
	}
	if (lastc == '\n') {
		STUNPUTC(dest);
	}
	if (in.fd >= 0)
		close(in.fd);
	if (in.buf)
		ckfree(in.buf);
	if (in.jp)
		exitstatus = waitforjob(in.jp);
	if (quoted == 0)
		recordregion(startloc, dest - stackblock(), 0);
	TRACE(("evalbackq: size=%d: \"%.*s\"\n",
		(dest - stackblock()) - startloc,
		(dest - stackblock()) - startloc,
		stackblock() + startloc));
	expdest = dest;
	INTON;
}



/*
 * Expand a variable, and return a pointer to the next character in the
 * input string.
 */

STATIC char *
evalvar(p, flag)
	char *p;
	{
	int subtype;
	int varflags;
	char *var;
	char *val;
	int c;
	int set;
	int special;
	int startloc;
	int quotes = flag & (EXP_FULL | EXP_CASE);

	varflags = *p++;
	subtype = varflags & VSTYPE;
	var = p;
	special = 0;
	if (! is_name(*p))
		special = 1;
	p = strchr(p, '=') + 1;
again: /* jump here after setting a variable with ${var=text} */
	if (special) {
		set = varisset(*var);
		val = NULL;
	} else {
		val = lookupvar(var);
		if (val == NULL || (varflags & VSNUL) && val[0] == '\0') {
			val = NULL;
			set = 0;
		} else
			set = 1;
	}
	startloc = expdest - stackblock();
	if (set && subtype != VSPLUS) {
		/* insert the value of the variable */
		if (special) {
			varvalue(*var, varflags & VSQUOTE, flag & EXP_FULL);
		} else {
			char const *syntax = (varflags & VSQUOTE)? DQSYNTAX : BASESYNTAX;

			while (*val) {
				if (quotes && syntax[*val] == CCTL)
					STPUTC(CTLESC, expdest);
				STPUTC(*val++, expdest);
			}
		}
	}
	if (subtype == VSPLUS)
		set = ! set;
	if (((varflags & VSQUOTE) == 0 || (*var == '@' && shellparam.nparam != 1))
	 && (set || subtype == VSNORMAL))
		recordregion(startloc, expdest - stackblock(), varflags & VSQUOTE);
	if (! set && subtype != VSNORMAL) {
		if (subtype == VSPLUS || subtype == VSMINUS) {
			argstr(p, flag);
		} else {
			char *startp;
			int saveherefd = herefd;
			struct nodelist *saveargbackq = argbackq;
			herefd = -1;
			argstr(p, 0);
			STACKSTRNUL(expdest);
			herefd = saveherefd;
			argbackq = saveargbackq;
			startp = stackblock() + startloc;
			if (subtype == VSASSIGN) {
				setvar(var, startp, 0);
				STADJUST(startp - expdest, expdest);
				varflags &=~ VSNUL;
				goto again;
			}
			/* subtype == VSQUESTION */
			if (*p != CTLENDVAR) {
				outfmt(&errout, "%s\n", startp);
				error((char *)NULL);
			}
			error("%.*s: parameter %snot set", p - var - 1,
				var, (varflags & VSNUL)? "null or " : nullstr);
		}
	}
	if (subtype != VSNORMAL) {	/* skip to end of alternative */
		int nesting = 1;
		for (;;) {
			if ((c = *p++) == CTLESC)
				p++;
			else if (c == CTLBACKQ || c == (CTLBACKQ|CTLQUOTE)) {
				if (set)
					argbackq = argbackq->next;
			} else if (c == CTLVAR) {
				if ((*p++ & VSTYPE) != VSNORMAL)
					nesting++;
			} else if (c == CTLENDVAR) {
				if (--nesting == 0)
					break;
			}
		}
	}
	return p;
}



/*
 * Test whether a specialized variable is set.
 */

STATIC int
varisset(name)
	char name;
	{
	char **ap;

	if (name == '!') {
		if (backgndpid == -1)
			return 0;
	} else if (name == '@' || name == '*') {
		if (*shellparam.p == NULL)
			return 0;
	} else if ((unsigned)(name -= '1') <= '9' - '1') {
		ap = shellparam.p;
		do {
			if (*ap++ == NULL)
				return 0;
		} while (--name >= 0);
	}
	return 1;
}



/*
 * Add the value of a specialized variable to the stack string.
 */

STATIC void
varvalue(name, quoted, allow_split)
	char name;
	{
	int num;
	char temp[32];
	char *p;
	int i;
	extern int exitstatus;
	char sep;
	char **ap;
	char const *syntax;

#define STRTODEST(p) \
	do {\
	if (allow_split) { \
		syntax = quoted? DQSYNTAX : BASESYNTAX; \
		while (*p) { \