Dan Nelson has kindly explained everything: > In the last episode (Oct 01), Andrew said: > > Thanks! I haven't thought about using expr. > > > > How come that my expr(1) manpage has nothing to say about -e option? > > In fact my expr(1) does not accept it. I have FreeBSD 4.10. I've just > > looked into a current manpage from www.freebsd.org, and it says > > something about 4.x compatibility. > > > > What is the best way to go if I need to write scripts now, but I'm > > planning to switch to 5.x later? Can I upgrade expr(1) now? If not, > > what should I do? > > In 4.x, expr does 64-bit math by default. Apparently POSIX requires > that expr use whatever the systems' "signed long" size is, so the > default was changed for 5.x, and -e was added to get the old behaviour. > > If you want your script to work on both, you'll have to do a feature > test. I started out just testing expr and expr -e, but it sort of > grew... The following script will check the shell's math, two ways of > calling expr, and finally fall back on calling bc. As long as you just > use the basic math operators, quote your "*"'s, and put spaces between > everything, all the methods should be compatible, and your script will > work on any bourne-compatible shell :) > > #! /bin/sh > > if [ x$(( 65536 * 65536 )) = "x4294967296" ] ; then > shellarith() { echo $(( $@ )) ; } > MATH="shellarith" > else > if [ x`expr 65536 "*" 65536` = "x4294967296" ] ; then > MATH="expr" > else > if [ x`expr -e 65536 "*" 65536 2>/dev/null` = x"4294967296" ] ; then > MATH="expr -e" > else > if [ x`echo 65536 "*" 65536 | bc` = "x4294967296" ] ; then > bcfunc() { echo "$@" | bc ; } > MATH="bcfunc" > else > echo "Can't do 64-bit math noway nohow" > fi > fi > fi > fi > > echo "Using $MATH" > bigval=`$MATH 65536 "*" 65536` > echo $bigval
Thank you very much! I think, I'll just assign MATH="expr" and change it to something else when I need it. Best regards, Andrew P. _______________________________________________ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"