Decimals in TCSH

Shell Programming and Scripting
1

Hello,
I want to run a loop with non-integer values (which I know I can't) so I've created a loop of integers and divided it by 10. However, these values are always rounded down to 1 significant figure. How do I get the script to keep and use the decimal value?

My script is as follows

# START RI LOOP
set RI_min = 10
set RI_max = 30
set RI_inc = 1

set RI = $RI_min
while ($RI <= $RI_max)

@ PI=$RI / 10
echo "PI = " $PI "g cm^-3"
echo $RI

RI now runs from 10 to 30 but PI is only ever 1, 2 or 3. Any ideas?
Thanks

2

Hi.

Here's one alternative:

#!/usr/bin/env tcsh

# @(#) s1	Demonstrate alternative for tcsh floating-point arithmetic.

echo
setenv LC_ALL C ; setenv LANG C
echo "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
echo "(Versions displayed with local utility version)"
sh -c "version >/dev/null 2>&1" && version "=o" tcsh
echo

alias acalc 'awk "BEGIN{ print \!* }" '

# START RI LOOP
set RI_min = 10
set RI_max = 30
set RI_inc = 1

set RI = $RI_min
while ($RI <= $RI_max)

# @ PI=$RI / 10
set PI = `acalc $RI / 10`
# echo "PI = " $PI "g cm^-3"
# echo $RI
echo " RI = $RI,  PI = " $PI "g cm^-3"
@ RI = $RI + $RI_inc

end

exit 0

producing:

% ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility version)
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0 
tcsh 6.14.00

 RI = 10,  PI =  1 g cm^-3
 RI = 11,  PI =  1.1 g cm^-3
 RI = 12,  PI =  1.2 g cm^-3
 RI = 13,  PI =  1.3 g cm^-3
 RI = 14,  PI =  1.4 g cm^-3
 RI = 15,  PI =  1.5 g cm^-3
 RI = 16,  PI =  1.6 g cm^-3
 RI = 17,  PI =  1.7 g cm^-3
 RI = 18,  PI =  1.8 g cm^-3
 RI = 19,  PI =  1.9 g cm^-3
 RI = 20,  PI =  2 g cm^-3
 RI = 21,  PI =  2.1 g cm^-3
 RI = 22,  PI =  2.2 g cm^-3
 RI = 23,  PI =  2.3 g cm^-3
 RI = 24,  PI =  2.4 g cm^-3
 RI = 25,  PI =  2.5 g cm^-3
 RI = 26,  PI =  2.6 g cm^-3
 RI = 27,  PI =  2.7 g cm^-3
 RI = 28,  PI =  2.8 g cm^-3
 RI = 29,  PI =  2.9 g cm^-3
 RI = 30,  PI =  3 g cm^-3

See Floating Point for a brief explanation of the alias.

Note that many people will advise you to avoid tcsh scripting. Using Bourne-shell relatives seems to work best for most projects. Here's an example of zsh illustrating built-in floating-point arithmetic (in later versions of ksh as well):

#!/usr/bin/env zsh

# @(#) s2	Demonstrate zsh floating-point arithmetic.

echo
set +o nounset
LC_ALL=C ; LANG=C ; export LC_ALL LANG
echo "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version "=o" $(_eat $0 $1) ksh
set -o nounset

echo
i=1
while (( i < 3.0 ))
do
  print " i = $i"
  (( i+=0.5 ))
done

exit 0

producing:

% ./s2

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0 
zsh 4.3.6
ksh 93s+

 i = 1
 i = 1.5
 i = 2.
 i = 2.5

Best wishes ... cheers, drl