So far I have this script:
#!/bin/sh
echo type in some numbers:
read input
From here on I'm stuck. Let's say input=30790148. What I want to do is add all of those integers up to get 3+0+7+9+0+1+4+8=32. How can I accomplish this?
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relevant QALucas Wieloch– Lucas Wieloch2018-10-30 12:47:14 +00:00Commented Oct 30, 2018 at 12:47
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1How would you do it mathematically?Dominique– Dominique2018-10-30 12:47:45 +00:00Commented Oct 30, 2018 at 12:47
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Sounds like a homework question... How do I ask homework questions on Stack Overflow. You are expected to make an effort.jww– jww2018-10-30 23:18:06 +00:00Commented Oct 30, 2018 at 23:18
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5 Answers
Another way not using external tools:
read -p "Type some number: " num
for((i=0;i<${#num};i++)); do ((sum+=${num:i:1})); done
echo "$sum"
5 Comments
Timo
What is it doing:
${num:i:1}. Seems like a number splitter, shifting one decimal -1- to the right by adding one to each fixed position i
mickp
@Timo It is a syntax for substrings. It means "return 1 character starting at ith character". Since
$num is a "string", ${num:i:1} is bash's equivalent of num[i] in other languages.Timo
Why not use $i here:
((sum+=${num:i:1}))mickp
It's not mandatory to use
$ in the arithmetic expansion (( expr )). From manual: ...shell variables may also be referenced by name without using the parameter expansion syntax.Timo
ok, Using
((sum+=${num:i})) without 1 will be a right shift by one reducing the array to the right.There are two core utilities, fold and paste, which you can use here (illustrated for input=12345):
fold -w1 <<< $input | paste -sd+ - | bc
fold -w1wraps the input line to a width of 1 character:$ fold -w1 <<< $input 1 2 3 4 5paste -sd+ -merges the input sequentially (-s), i.e., into a single line, with a+delimiter (-d+), reading from standard input (the final-; optional for GNUpaste):$ fold -w1 <<< $input | paste -sd+ - 1+2+3+4+5bcthen calculates the sum:$ fold -w1 <<< $input | paste -sd+ - | bc 15
Comments
This one using sed and bc
echo "12345" | sed -e 's/\(.\)/\1\+0/g' | bc
It's a bit hackish though since the +0 is not intuitive
Edit: Using & from @PaulHodges' answer, this would shorten to:
echo "12345" | sed 's/./&+0/g' | bc
4 Comments
Benjamin W.
This works fine with
bc, but watch out with prepending zeroes to numbers; in some places, the number will suddenly be interpreted as octal.
ssemilla
Yeah, it's really abusing the fact that
bc will interpret everything here as decimal. I was gunning for the shortest code possible e.g. sed 's/./&+0/g' | bcssemilla
I can't think of anything right now, but imagine a tool that got fed
1+02+09+0. Since 09 is not a valid octal number, it would definitely error out.
Paul Hodges
Sorry, figured out what you meant and deleted my comment, lol
This awk one-liner may help you:
awk '{for(i=1;i<=NF;i++)s+=$i}END{print s}' FS="" <<< yourString
for example:
kent$ awk '{for(i=1;i<=NF;i++)s+=$i}END{print s}' FS=""<<< "123456789"
45
Comments
With sed and bc -
input=30790148; echo $input | sed 's/[0-9]/&+/g; s/$/0/;' | bc
If you don't have GNU sed you might need to line break the commands instead of using a semicolon.
input=30790148;
echo $input |
sed '
s/[0-9]/&+/g
s/$/0/
' | bc
3 Comments
ssemilla
Hey, we can merge our answers and simplify it further
sed 's/./&+0/g' | bc. TIL of &, thank you.Paul Hodges
c.f. the comments on your answer - add the 0 separately at the end.
ssemilla
Yep, I was only trying to make it as short as possible. Anyway, thanks for
&, another tool in the toolbox.