eval.c

一个开放源代码的 AT&T 的 Korn Shell 的复制品, 支持大多数 ksh89 的特性。

/*
 * Expansion - quoting, separation, substitution, globbing
 */

#include "sh.h"
#include <pwd.h>
#include "ksh_dir.h"
#include "ksh_stat.h"

/*
 * string expansion
 *
 * first pass: quoting, IFS separation, ~, ${}, $() and $(()) substitution.
 * second pass: alternation ({,}), filename expansion (*?[]).
 */

/* expansion generator state */
typedef struct Expand {
	/* int  type; */	/* see expand() */
	const char *str;	/* string */
	union {
		const char **strv;/* string[] */
		struct shf *shf;/* file */
	} u;			/* source */
	struct tbl *var;	/* variable in ${var..} */
	short	split;		/* split "$@" / call waitlast $() */
} Expand;

#define	XBASE		0	/* scanning original */
#define	XSUB		1	/* expanding ${} string */
#define	XARGSEP		2	/* ifs0 between "$*" */
#define	XARG		3	/* expanding $*, $@ */
#define	XCOM		4	/* expanding $() */
#define XNULLSUB	5	/* "$@" when $# is 0 (don't generate word) */

/* States used for field splitting */
#define IFS_WORD	0	/* word has chars (or quotes) */
#define IFS_WS		1	/* have seen IFS white-space */
#define IFS_NWS		2	/* have seen IFS non-white-space */

static	int	varsub ARGS((Expand *xp, char *sp, char *word, int *stypep, int *slenp));
static	int	comsub ARGS((Expand *xp, char *cp));
static	char   *trimsub ARGS((char *str, char *pat, int how));
static	void	glob ARGS((char *cp, XPtrV *wp, int markdirs));
static	void	globit ARGS((XString *xs, char **xpp, char *sp, XPtrV *wp,
			     int check));
static char	*maybe_expand_tilde ARGS((char *p, XString *dsp, char **dpp,
					  int isassign));
static	char   *tilde ARGS((char *acp));
static	char   *homedir ARGS((char *name));
#ifdef BRACE_EXPAND
static void	alt_expand ARGS((XPtrV *wp, char *start, char *exp_start,
				 char *end, int fdo));
#endif

/* compile and expand word */
char *
substitute(cp, f)
	const char *cp;
	int f;
{
	struct source *s, *sold;

	sold = source;
	s = pushs(SWSTR, ATEMP);
	s->start = s->str = cp;
	source = s;
	if (yylex(ONEWORD) != LWORD)
		internal_errorf(1, "substitute");
	source = sold;
	afree(s, ATEMP);
	return evalstr(yylval.cp, f);
}

/*
 * expand arg-list
 */
char **
eval(ap, f)
	register char **ap;
	int f;
{
	XPtrV w;

	if (*ap == NULL)
		return ap;
	XPinit(w, 32);
	XPput(w, NULL);		/* space for shell name */
#ifdef	SHARPBANG
	XPput(w, NULL);		/* and space for one arg */
#endif
	while (*ap != NULL)
		expand(*ap++, &w, f);
	XPput(w, NULL);
#ifdef	SHARPBANG
	return (char **) XPclose(w) + 2;
#else
	return (char **) XPclose(w) + 1;
#endif
}

/*
 * expand string
 */
char *
evalstr(cp, f)
	char *cp;
	int f;
{
	XPtrV w;

	XPinit(w, 1);
	expand(cp, &w, f);
	cp = (XPsize(w) == 0) ? null : (char*) *XPptrv(w);
	XPfree(w);
	return cp;
}

/*
 * expand string - return only one component
 * used from iosetup to expand redirection files
 */
char *
evalonestr(cp, f)
	register char *cp;
	int f;
{
	XPtrV w;

	XPinit(w, 1);
	expand(cp, &w, f);
	switch (XPsize(w)) {
	case 0:
		cp = null;
		break;
	case 1:
		cp = (char*) *XPptrv(w);
		break;
	default:
		cp = evalstr(cp, f&~DOGLOB);
		break;
	}
	XPfree(w);
	return cp;
}

/* for nested substitution: ${var:=$var2} */
typedef struct SubType {
	short	stype;		/* [=+-?%#] action after expanded word */
	short	base;		/* begin position of expanded word */
	short	f;		/* saved value of f (DOPAT, etc) */
	struct tbl *var;	/* variable for ${var..} */
	short	quote;		/* saved value of quote (for ${..[%#]..}) */
	struct SubType *prev;	/* old type */
	struct SubType *next;	/* poped type (to avoid re-allocating) */
} SubType;

void
expand(cp, wp, f)
	char *cp;		/* input word */
	register XPtrV *wp;	/* output words */
	int f;			/* DO* flags */
{
	register int UNINITIALIZED(c);
	register int type;	/* expansion type */
	register int quote = 0;	/* quoted */
	XString ds;		/* destination string */
	register char *dp, *sp;	/* dest., source */
	int fdo, word;		/* second pass flags; have word */
	int doblank;		/* field spliting of parameter/command subst */
	Expand x;		/* expansion variables */
	SubType st_head, *st;
	int UNINITIALIZED(newlines); /* For trailing newlines in COMSUB */
	int saw_eq, tilde_ok;
	int make_magic;

	if (cp == NULL)
		internal_errorf(1, "expand(NULL)");
	/* for alias, readonly, set, typeset commands */
	if ((f & DOVACHECK) && is_wdvarassign(cp)) {
		f &= ~(DOVACHECK|DOBLANK|DOGLOB|DOTILDE);
		f |= DOASNTILDE;
	}
	if (Flag(FNOGLOB))
		f &= ~DOGLOB;
	if (Flag(FMARKDIRS))
		f |= DOMARKDIRS;
#ifdef BRACE_EXPAND
	if (Flag(FBRACEEXPAND) && (f & DOGLOB))
		f |= DOBRACE_;
#endif /* BRACE_EXPAND */

	Xinit(ds, dp, 128, ATEMP);	/* init dest. string */
	type = XBASE;
	sp = cp;
	fdo = 0;
	saw_eq = 0;
	tilde_ok = (f & (DOTILDE|DOASNTILDE)) ? 1 : 0; /* must be 1/0 */
	doblank = 0;
	make_magic = 0;
	word = (f&DOBLANK) ? IFS_WS : IFS_WORD;
	st_head.next = (SubType *) 0;
	st = &st_head;

	while (1) {
		Xcheck(ds, dp);

		switch (type) {
		  case XBASE:	/* original prefixed string */
			c = *sp++;
			switch (c) {
			  case EOS:
				c = 0;
				break;
			  case CHAR:
				c = *sp++;
				break;
			  case QCHAR:
				quote |= 2; /* temporary quote */
				c = *sp++;
				break;
			  case OQUOTE:
				word = IFS_WORD;
				tilde_ok = 0;
				quote = 1;
				continue;
			  case CQUOTE:
				quote = 0;
				continue;
			  case COMSUB:
				tilde_ok = 0;
				if (f & DONTRUNCOMMAND) {
					word = IFS_WORD;
					*dp++ = '$'; *dp++ = '(';
					while (*sp != '\0') {
						Xcheck(ds, dp);
						*dp++ = *sp++;
					}
					*dp++ = ')';
				} else {
					type = comsub(&x, sp);
					if (type == XCOM && (f&DOBLANK))
						doblank++;
					sp = strchr(sp, 0) + 1;
					newlines = 0;
				}
				continue;
			  case EXPRSUB:
				word = IFS_WORD;
				tilde_ok = 0;
				if (f & DONTRUNCOMMAND) {
					*dp++ = '$'; *dp++ = '('; *dp++ = '(';
					while (*sp != '\0') {
						Xcheck(ds, dp);
						*dp++ = *sp++;
					}
					*dp++ = ')'; *dp++ = ')';
				} else {
					struct tbl v;
					char *p;

					v.flag = DEFINED|ISSET|INTEGER;
					v.type = 10; /* not default */
					v.name[0] = '\0';
					v_evaluate(&v, substitute(sp, 0),
						KSH_UNWIND_ERROR);
					sp = strchr(sp, 0) + 1;
					for (p = str_val(&v); *p; ) {
						Xcheck(ds, dp);
						*dp++ = *p++;
					}
				}
				continue;
			  case OSUBST: /* ${{#}var{:}[=+-?#%]word} */
			  /* format is:
			   *   OSUBST [{x] plain-variable-part \0
			   *     compiled-word-part CSUBST [}x]
			   * This is were all syntax checking gets done...
			   */
			  {
				char *varname = ++sp; /* skip the { or x (}) */
				int stype;
				int slen;

				sp = strchr(sp, '\0') + 1; /* skip variable */
				type = varsub(&x, varname, sp, &stype, &slen);
				if (type < 0) {
					char endc;
					char *str, *end;

					end = (char *) wdscan(sp, CSUBST);
					/* ({) the } or x is already skipped */
					endc = *end;
					*end = EOS;
					str = snptreef((char *) 0, 64, "%S",
							varname - 1);
					*end = endc;
					errorf("%s: bad substitution", str);
				}
				if (f&DOBLANK)
					doblank++;
				tilde_ok = 0;
				if (type == XBASE) {	/* expand? */
					if (!st->next) {
						SubType *newst;

						newst = (SubType *) alloc(
							sizeof(SubType), ATEMP);
						newst->next = (SubType *) 0;
						newst->prev = st;
						st->next = newst;
					}
					st = st->next;
					st->stype = stype;
					st->base = Xsavepos(ds, dp);
					st->f = f;
					st->var = x.var;
					st->quote = quote;
					/* skip qualifier(s) */
					if (stype)
						sp += slen;
					switch (stype & 0x7f) {
					  case '#':
					  case '%':
						/* ! DOBLANK,DOBRACE_,DOTILDE */
						f = DOPAT | (f&DONTRUNCOMMAND)
						    | DOTEMP_;
						quote = 0;
						/* Prepend open pattern (so |
						 * in a trim will work as
						 * expected)
						 */
						*dp++ = MAGIC;
						*dp++ = '@' + 0x80;
						break;
					  case '=':
						/* Enabling tilde expansion
						 * after :'s here is
						 * non-standard ksh, but is
						 * consistent with rules for
						 * other assignments.  Not
						 * sure what POSIX thinks of
						 * this.
						 * Not doing tilde expansion
						 * for integer variables is a
						 * non-POSIX thing - makes
						 * sense though, since ~ is
						 * a arithmetic operator.
						 */
						if (!(x.var->flag & INTEGER))
							f |= DOASNTILDE|DOTILDE;
						f |= DOTEMP_;
						/* These will be done after the
						 * value has been assigned.
						 */
						f &= ~(DOBLANK|DOGLOB|DOBRACE_);
						tilde_ok = 1;
						break;
					  case '?':
						f &= ~DOBLANK;
						f |= DOTEMP_;
						/* fall through */
					  default:
						/* Enable tilde expansion */
						tilde_ok = 1;
						f |= DOTILDE;
					}
				} else
					/* skip word */
					sp = (char *) wdscan(sp, CSUBST);
				continue;
			  }
			  case CSUBST: /* only get here if expanding word */
				sp++; /* ({) skip the } or x */
				tilde_ok = 0;	/* in case of ${unset:-} */
				*dp = '\0';
				quote = st->quote;
				f = st->f;
				if (f&DOBLANK)
					doblank--;
				switch (st->stype&0x7f) {
				  case '#':
				  case '%':
					/* Append end-pattern */
					*dp++ = MAGIC; *dp++ = ')'; *dp = '\0';
					dp = Xrestpos(ds, dp, st->base);
					/* Must use st->var since calling
					 * global would break things
					 * like x[i+=1].
					 */
					x.str = trimsub(str_val(st->var),
						dp, st->stype);
					type = XSUB;
					if (f&DOBLANK)
						doblank++;
					st = st->prev;
					continue;
				  case '=':
					/* Restore our position and substitute
					 * the value of st->var (may not be
					 * the assigned value in the presence
					 * of integer/right-adj/etc attributes).
					 */
					dp = Xrestpos(ds, dp, st->base);
					/* Must use st->var since calling
					 * global would cause with things
					 * like x[i+=1] to be evaluated twice.
					 */
					/* Note: not exported by FEXPORT
					 * in at&t ksh.
					 */
					/* XXX POSIX says readonly is only
					 * fatal for special builtins (setstr
					 * does readonly check).
					 */
					setstr(st->var, debunk(
						(char *) alloc(strlen(dp) + 1,
							ATEMP), dp),
						KSH_UNWIND_ERROR);
					x.str = str_val(st->var);
					type = XSUB;
					if (f&DOBLANK)
						doblank++;
					st = st->prev;
					continue;
				  case '?':
				    {
					char *s = Xrestpos(ds, dp, st->base);

					errorf("%s: %s", st->var->name,
					    dp == s ? 
					      "parameter null or not set"
					    : (debunk(s, s), s));
				    }
				}
				st = st->prev;
				type = XBASE;
				continue;

			  case OPAT: /* open pattern: *(foo|bar) */
				/* Next char is the type of pattern */
				make_magic = 1;
				c = *sp++ + 0x80;
				break;

			  case SPAT: /* pattern seperator (|) */
				make_magic = 1;
				c = '|';
				break;

			  case CPAT: /* close pattern */
				make_magic = 1;
				c = /*(*/ ')';
				break;
			}
			break;

		  case XNULLSUB:
			/* Special case for "$@" (and "${foo[@]}") - no