Hi folks,
Here's a diff to expr(1) that does three things I feel make it more useful:
+ Makes it 64-bit capable on 64-bit architectures by changing relevant
int:s to long:s. I often use expr as a quick calculator for example when
partitioning disks and such, and frequently find myself up against the
32 bit signed integer limits.
+ Makes it able to use C-style radix prefixes to integers in order to do
calculations in octal and hexadecimal. In the olden days, early '80:s to
be specific, I worked at a company that produced a unix flavour called
D-NIX, which had this neat feature in its expr(1). It makes it a breeze
to make quick radix conversions, for example. And I guess the habit
stuck with me, for to this day it frustrates me not to be able to use
expr for that. :-) I hope others find it useful too. For example:
skynet:/usr/src/bin/expr# expr 0x1ffff + 15
131086
skynet:/usr/src/bin/expr#
+ Makes it able to output calculation results in hex and octal. This is
of course the reverse functionality to the previous. Works like this:
skynet:/usr/src/bin/expr# expr -x 16383
3fff
skynet:/usr/src/bin/expr# expr -o 16383
37777
skynet:/usr/src/bin/expr# expr -X 16383
3FFF
skynet:/usr/src/bin/expr# expr -cx 16383
0x3fff
skynet:/usr/src/bin/expr#
Now, the downside is that the latter two changes will subtly change
expr:s semantics, in the following ways:
- Hexadecimal numbers (starting with 0x or 0X) is no longer recognized
as strings. (The common construct expr 'X'$FOO = 'X' would still work as
expected, of course.) Probably not a big concern.
- Since expr previously ignored switches altogether, strings starting
with '-' will no longer be recognized as strings, but probably generate
a "usage:" error message instead. This can be circumvented by the --
notation, and that particular form was actually supported before as
well. But still this might be a problem since there is a slim chance it
can break current shell scripts. I can't think of a better / more
backwards compatible way to implement different output radixes though.
- And of course the 32 bit signed integer edge cases will instead be 64
bit signed integer edge cases on 64-bit architectures. Probably not a
problem either.
- Oh, and I don't know if these changes breaks POSIX compliance.
(And as I'm about to post this at 04:00 in the morning, it comes to mind
that I might have read somewhere that submitted diffs should only change
one behaviour at a time. If that's the case I apologize.)
If these are worthy changes, they need testing of course (on both 32-
and 64-bit architectures), and if so I'll make a diff for the man page
as well. (And hopefully I didn't f*ck up the enclosed diff...)
Regards,
/Benny
----8<--------8<--------8<--------8<--------8<---- (cut)
Index: expr.c
===================================================================
RCS file: /cvs/src/bin/expr/expr.c,v
retrieving revision 1.17
diff -u -r1.17 expr.c
--- expr.c 21 Jun 2006 18:28:24 -0000 1.17
+++ expr.c 15 Jan 2011 03:00:26 -0000
@@ -14,11 +14,11 @@
#include <regex.h>
#include <err.h>
-struct val *make_int(int);
+struct val *make_int(long);
struct val *make_str(char *);
void free_value(struct val *);
-int is_integer(struct val *, int *);
-int to_integer(struct val *);
+int is_integer(struct val *, long *);
+long to_integer(struct val *);
void to_string(struct val *);
int is_zero_or_null(struct val *);
void nexttoken(int);
@@ -44,7 +44,7 @@
union {
char *s;
- int i;
+ long i;
} u;
};
@@ -53,7 +53,7 @@
char **av;
struct val *
-make_int(int i)
+make_int(long i)
{
struct val *vp;
@@ -92,11 +92,14 @@
/* determine if vp is an integer; if so, return it's value in *r */
int
-is_integer(struct val *vp, int *r)
+is_integer(struct val *vp, long *r)
{
char *s;
- int neg;
- int i;
+ long neg;
+ long i, d;
+ long radix=10;
+ static char *digits="0123456789abcdef";
+ char *dp;
if (vp->type == integer) {
*r = vp->u.i;
@@ -105,7 +108,8 @@
/*
* POSIX.2 defines an "integer" as an optional unary minus
- * followed by digits.
+ * followed by digits. We also consider C style octal and
+ * hexadecimal prefix notation part of an integer.
*/
s = vp->u.s;
i = 0;
@@ -113,14 +117,21 @@
neg = (*s == '-');
if (neg)
s++;
+ if (*s=='0') {
+ radix=8; s++;
+ if (*s=='x' || *s=='X') {
+ radix=16; s++;
+ }
+ }
while (*s) {
- if (!isdigit(*s))
+ if ((dp = strchr(digits, tolower(*s)))==NULL)
return 0;
+ if ((d = dp-digits) >= radix)
+ return 0; /* Invalid digit for radix -> string */
- i *= 10;
- i += *s - '0';
-
+ i *= radix;
+ i += d;
s++;
}
@@ -133,10 +144,10 @@
/* coerce to vp to an integer */
-int
+long
to_integer(struct val *vp)
{
- int r;
+ long r;
if (vp->type == integer)
return 1;
@@ -375,7 +386,7 @@
{
struct val *l, *r;
enum token op;
- int v = 0, li, ri;
+ long v = 0, li, ri;
l = eval3();
while ((op = token) == EQ || op == NE || op == LT || op == GT ||
@@ -491,16 +502,48 @@
int
main(int argc, char *argv[])
{
- struct val *vp;
+ struct val *vp;
+ int oradix=10;
+ int cprefix=0;
+ int c;
+ extern char *__progname;
(void) setlocale(LC_ALL, "");
- if (argc > 1 && !strcmp(argv[1], "--"))
- argv++;
+ while ((c=getopt(argc, argv, "coxX")) != -1) {
+ switch (c) {
+ case 'c':
+ cprefix=1;
+ break;
+ case 'o':
+ oradix=8;
+ break;
+ case 'x':
+ oradix=16;
+ break;
+ case 'X':
+ oradix=-16;
+ break;
+ default:
+ fprintf(stderr,
+ "usage: %s [-coxX] <expression>\n",
+ __progname);
+ exit(2); /* Tell user invalid expression */
+ }
+ }
+ argc -= optind;
+ argv += optind;
- av = argv + 1;
+ av = argv;
nexttoken(0);
+
+ /* In case there is only one operand, make sure it is validated
+ * as an integer as well, in case we for example want to print it
+ * in a different radix.
+ */
+ (void) to_integer(tokval);
+
vp = eval0();
if (token != EOI) {
@@ -508,9 +551,21 @@
/* NOTREACHED */
}
- if (vp->type == integer)
- printf("%d\n", vp->u.i);
- else
+ if (vp->type == integer) {
+ switch (oradix) {
+ case 8:
+ printf("%s%lo\n", cprefix ? "0" : "", vp->u.i);
+ break;
+ case 16:
+ printf("%s%lx\n", cprefix ? "0x" : "", vp->u.i);
+ break;
+ case -16:
+ printf("%s%lX\n", cprefix ? "0X" : "", vp->u.i);
+ break;
+ default:
+ printf("%ld\n", vp->u.i); break;
+ }
+ } else
printf("%s\n", vp->u.s);
exit(is_zero_or_null(vp));
----8<--------8<--------8<--------8<--------8<---- (cut)
--
internetlabbet.se / work: +46 8 551 124 80 / "Words must
Benny Lvfgren / mobile: +46 70 718 11 90 / be weighed,
/ fax: +46 8 551 124 89 / not counted."
/ email: benny -at- internetlabbet.se
