per my mail, avoid slow strtod() and ferror().
maybe the strtod screen should go into all 3 or 4
versions of strtod (or maybe there should be fewer
versions) instead.

Reference: /n/sources/patch/applied/faster-awk
Date: Sat Feb  4 11:08:35 CET 2006

--- /sys/src/cmd/awk/lib.c	Sat Feb  4 11:07:27 2006
+++ /sys/src/cmd/awk/lib.c	Sat Feb  4 11:07:24 2006
@@ -673,6 +673,32 @@
 {
 	double r;
 	char *ep;
+
+	/*
+	 * fast could-it-be-a-number check before calling strtod,
+	 * which takes a surprisingly long time to reject non-numbers.
+	 */
+	switch (*s) {
+	case '0': case '1': case '2': case '3': case '4':
+	case '5': case '6': case '7': case '8': case '9':
+	case '\t':
+	case '\n':
+	case '\v':
+	case '\f':
+	case '\r':
+	case ' ':
+	case '-':
+	case '+':
+	case '.':
+	case 'n':		/* nans */
+	case 'N':
+	case 'i':		/* infs */
+	case 'I':
+		break;
+	default:
+		return 0;	/* can't be a number */
+	}
+
 	errno = 0;
 	r = strtod(s, &ep);
 	if (ep == s || r == HUGE_VAL || errno == ERANGE)
--- /sys/src/cmd/awk/run.c	Sat Feb  4 11:07:44 2006
+++ /sys/src/cmd/awk/run.c	Sat Feb  4 11:07:38 2006
@@ -133,6 +133,7 @@
 
 Cell *execute(Node *u)	/* execute a node of the parse tree */
 {
+	int nobj;
 	Cell *(*proc)(Node **, int);
 	Cell *x;
 	Node *a;
@@ -149,10 +150,11 @@
 				recbld();
 			return(x);
 		}
-		if (notlegal(a->nobj))	/* probably a Cell* but too risky to print */
+		nobj = a->nobj;
+		if (notlegal(nobj))	/* probably a Cell* but too risky to print */
 			FATAL("illegal statement");
-		proc = proctab[a->nobj-FIRSTTOKEN];
-		x = (*proc)(a->narg, a->nobj);
+		proc = proctab[nobj-FIRSTTOKEN];
+		x = (*proc)(a->narg, nobj);
 		if (isfld(x) && !donefld)
 			fldbld();
 		else if (isrec(x) && !donerec)
@@ -1540,6 +1542,7 @@
 
 Cell *printstat(Node **a, int n)	/* print a[0] */
 {
+	int r;
 	Node *x;
 	Cell *y;
 	FILE *fp;
@@ -1553,14 +1556,15 @@
 		fputs(getsval(y), fp);
 		tempfree(y);
 		if (x->nnext == NULL)
-			fputs(*ORS, fp);
+			r = fputs(*ORS, fp);
 		else
-			fputs(*OFS, fp);
+			r = fputs(*OFS, fp);
+		if (r == EOF)
+			FATAL("write error on %s", filename(fp));
 	}
 	if (a[1] != 0)
-		fflush(fp);
-	if (ferror(fp))
-		FATAL("write error on %s", filename(fp));
+		if (fflush(fp) == EOF)
+			FATAL("write error on %s", filename(fp));
 	return(True);
 }