This is at least supported by FreeBSD's units(1) as well as by
systemd/Linux.
With a personal library like this:
$ cat ~/units.lib
assload 8 stone
butt 2 hogshead
buttload 6 seams
solarmass 1.98847e30 kg
I can convert my mass into more convenient units:
$ units -f '' -f ~/units.lib
622 units, 67 prefixes
You have: 93 kg
You want: assloads
* 1.8306241
/ 0.54626178
You have: 93 kg
You want: solarmasses
* 4.6769627e-29
/ 2.1381398e+28
Note that the imperial buttload is a unit of volume while the assload is a unit
of mass:
You have: buttload
You want: assload
conformability error
1.6914754 m^3
50.802345 kg
On the other hand, you need about 4^28 standard donkeys to lug the sun
around:
You have: solarmass
You want: assload
* 3.9141303e+28
/ 2.554846e-29
OK?
diff --git units.1 units.1
index d7a45f729b3..916d1b03d32 100644
--- units.1
+++ units.1
@@ -79,6 +79,11 @@ The options are as follows:
.Bl -tag -width Ds
.It Fl f Ar filename
Specifies the name of the units data file to load.
+This options may be specified multiple times.
+The standard units library is read if
+.Ar filename
+is the empty string.
+This allows extending the standard units library with a personal library.
.It Fl q
Suppresses prompting of the user for units and the display of statistics
about the number of units loaded.
diff --git units.c units.c
index 98af5031fb1..488795c78cb 100644
--- units.c
+++ units.c
@@ -100,7 +100,6 @@ readunits(char *userfile)
int len, linenum, i;
FILE *unitfile;
- unitcount = 0;
linenum = 0;
if (userfile) {
@@ -626,8 +625,7 @@ main(int argc, char **argv)
struct unittype have, want;
char havestr[81], wantstr[81];
int optchar;
- char *userfile = 0;
- int quiet = 0;
+ int quiet = 0, units_read = 0;
extern char *optarg;
extern int optind;
@@ -638,7 +636,8 @@ main(int argc, char **argv)
while ((optchar = getopt(argc, argv, "vqf:")) != -1) {
switch (optchar) {
case 'f':
- userfile = optarg;
+ units_read = 1;
+ readunits(*optarg == '\0' ? NULL : optarg);
break;
case 'q':
quiet = 1;
@@ -662,7 +661,8 @@ main(int argc, char **argv)
if (argc != 3 && argc != 2 && argc != 0)
usage();
- readunits(userfile);
+ if (!units_read)
+ readunits(NULL);
if (pledge("stdio", NULL) == -1)
err(1, "pledge");
--
I'm not entirely sure you are real.
