Provide an environment variabloe, EXPR_COMPAT, which disables option

parsing for compatibility with old implementations.

2 files changed, 27 insertions, 10 deletions

diff --git a/bin/expr/expr.1 b/bin/expr/expr.1
index df4c70b..4669000 100644
--- a/bin/expr/expr.1
+++ b/bin/expr/expr.1
@@ -111,7 +111,9 @@ otherwise 0.
 .Pp
 Parentheses are used for grouping in the usual manner.
 .Pp
-This version of
+Unless the
+.Ev EXPR_COMPAT
+variable is defined in the process environment, this version of
 .Nm
 adheres to the
 .Tn POSIX
@@ -141,6 +143,15 @@ The syntax of the
 command in general is historic and inconvenient.
 New applications are advised to use shell arithmetic rather than
 .Nm .
+.Sh ENVIRONMENT
+.Bl -tag -compact -width EXPR_COMPAT
+.It Ev EXPR_COMPAT
+If set,
+.Nm
+will emulate historic
+.Nm
+implementations which did not obey the Utility Syntax Guidelines.
+.El
 .Sh EXAMPLES
 .Bl -bullet
 .It
@@ -216,7 +227,10 @@ the expression is invalid.
 The
 .Nm
 utility conforms to
-.St -p1003.1-2001 .
+.St -p1003.1-2001 ,
+provided that the
+.Ev EXPR_COMPAT
+environment variable is not defined.
 .Tn POSIX
 does not specify whether arithmetic overflow is detected, nor does it specify
 the possible range of integer arguments to
diff --git a/bin/expr/expr.y b/bin/expr/expr.y
index bc40bf3..3026f52 100644
--- a/bin/expr/expr.y
+++ b/bin/expr/expr.y
@@ -270,14 +270,17 @@ main(int argc, char *argv[])
 	int c;
 
 	setlocale (LC_ALL, "");
-	while ((c = getopt(argc, argv, "")) != -1)
-		switch (c) {
-		default:
-			fprintf(stderr, "usage: expr [--] expression\n");
-			exit(ERR_EXIT);
-		}
-
-	av = argv + optind;
+	if (getenv("EXPR_COMPAT") != NULL) {
+		av = argv + 1;
+	} else {
+		while ((c = getopt(argc, argv, "")) != -1)
+			switch (c) {
+			default:
+				fprintf(stderr,"usage: expr [--] expression\n");
+				exit(ERR_EXIT);
+			}
+		av = argv + optind;
+	}
 
 	yyparse();