Is there a certain syntax to use while using fractions or decimals in a bash script?
I tried using the following script:
#!/bin/bash
{
n=9
echo "$n"
for (( i=.5; $i <10; i++ ));
do
let "c=$i+1"
echo $i "+" $c
done
}
This works with i=1, but it generates a syntax error when I put .5.
Is there also a way to go by increments of 0.5 in the loop?
Thank you!
If you really want to use floating point in bash then you will find bc useful.
say you want 10 iterations, each of size 0.5
#!/bin/bash
Initial=1
Step=0.5
Count=10
for (( i=0; i < $Count; i++ ))
do
Value=$(echo "$Initial + ( $Step * $i )" | bc)
echo $Value
done
Will print:
$ ./t.sh
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Alternatively exit the loop based upon Value thusly:
Initial=1
Step=0.5
Value=$Initial
TermValue=6.1
for (( i=0; $(echo "$Value < $TermValue" | bc); i++ ))
do
Value=$(echo "$Value + $Step" | bc)
echo $Value
done
It's not possible to use floats in bash, but you can
#!/bin/bash
for (( i=5; $i <100; i+=10 )); do
(( c = $i + 10 ))
echo "${i: 0:-1}.${i: -1} + ${c: 0:-1}.${c: -1}"
done
i.e. multiply everything by 10 and then print the first n-1 digits, a decimal point and then the last digit. Of course this is very limited in being useful.
The shell itself won't support floats, but you can use bc if it's available, or awk, which is almost always available. Both will support floating point operations (so will perl, python, and some other tools)
AirBoxOmega:~ d$ printf ".%i %i 3.14\n" {1..16}
.1 2 3.14
.3 4 3.14
.5 6 3.14
.7 8 3.14
.9 10 3.14
.11 12 3.14
.13 14 3.14
.15 16 3.14
AirBoxOmega:~ d$ printf ".%i %i 3.14\n" {1..16}|awk '{print $1*$2/$3}'
0.0636943
0.382166
0.955414
1.78344
2.86624
0.420382
0.579618
0.764331
AirBoxOmega:~ d$ printf ".%i * %i / 3.14\n" {1..16}|bc -l
.06369426751592356687
.38216560509554140127
.95541401273885350318
1.78343949044585987261
2.86624203821656050955
.42038216560509554140
.57961783439490445859
.76433121019108280254
You can use seq and bc:
for i in $(seq 0.5 10); do
c=$(echo "$i+1" | bc);
echo $i "+" $c;
done
bashdoes not implement floating-point arithmetic.