add script examples

These scripts add numbers (one per line) from standard input.

usage

Add numbers from keyboard:

path/to/executable
6
7
8
Ctrl+d

Add numbers piped from another command:

ls -ld *   # long listing
ls -ld * | tr -s ' '  # reduce consecutive runs of spaces to a single space
ls -ld * | tr -s ' ' | cut -d ' ' -f 5  # output only size field
ls -ld * | tr -s ' ' | cut -d ' ' -f 5 | path/to/executable  # add sizes

bash

Sum=0                     # initialize accumulator
while read Num ; do       # loop while input exists assigning each line to Num
  Sum=$(( $Sum + $Num ))  # add input number to Sum
done                      # end of while block
echo $Sum                 # print total

scheme

(define (sum in-list)                ; function with 1 list arg
  (let ((value (read)))              ; local var, scheme object from STDIN
    (if (eof-object? value)          ; if end of file
      (begin                         ; group statements
        (display (apply + in-list))  ; add list elements, print
        (newline))                   ; print newline
      (sum (cons value in-list)))))  ; construct new list, recursive call
(sum '())                            ; call function with empty list

awk

{ Sum += $1 }      # integer accumulator + 1st field of each input line
                   # no loop, input read automatically
                   # no initialization, new variables default to zero
END { print Sum }  # END matches after last input line

perl

use strict ;               # enable error checking
use warnings ;             # enable more error checking
my $Sum = 0 ;              # initialize accumulator (scaler, local scope)
$Sum += $_ for <STDIN> ;   # one-line foreach loop
                           # < > is file read operator
                           # $_ is default loop variable, add to accumulator
print "$Sum\n" ;           # explicit newline

tcl

set Sum 0                                 # initialize accumulator
foreach Num [read stdin] {incr Sum $Num}  # read STDIN, assign each line to Num,
                                          # add Num to Sum
puts $Sum                                 # print

# alternate method
set Nums [split [read -nonewline stdin] \n]  # read STDIN,  split on NL to list,
                                             # assign to Nums
puts [tcl::mathop::+ {*}$Nums]               # expand list, sum, print

python

import sys              # use sys module
Sum = 0                 # initialize accumulator
for Num in sys.stdin :  # loop over lines from STDIN
  Sum += int(Num)       # convert strings to integers, add to accumulator
                        # block defined by indentation
print Sum               # print

lua

Sum = 0                                       -- initialize accumulator
for Num in io.lines() do Sum = Sum + Num end  -- loop over lines from STDIN
                                              -- add numeric value to Sum
print(math.floor(Sum))                        -- convert default float to int

php

<?php                                      // opening HTML tag
$str = file_get_contents("php://stdin") ;  // read stdin to string
$arr = explode("\n", $str) ;               // split string to array on newlines
echo array_sum($arr) . "\n" ;              // sum array elements, print
?>                                         // closing HTML tag

javascript

const fs = require("fs")                                // file handle for stdin
const numarr = fs.readFileSync(0, "utf-8").split("\n")  // read, split to array
// convert strings to integers, reduce with summing function, print
console.log(numarr.reduce((acc, val) => {return acc + Number(val)}, 0))

ruby

# read lines, convert strings to integers, reduce with summing function, print
puts STDIN.reduce {|sum, num| sum.to_i + num.to_i }

scala

import io.Source  // contains stdin
// read stdin, make it a string, split on newlines, convert to list,
// change strings to integers, add them up, print
println(Source.stdin.mkString.split("[\n]+").toList.map(x => x.toInt).sum)

clojure

(println                                    ; output with newline
  (reduce +                                 ; sum elements of list
    (map #(Integer/parseInt %)              ; strings to integers (Java method)
      (line-seq                             ; returns sequence
        (java.io.BufferedReader. *in*)))))  ; read STDIN (Java method)

elixir

String.split(IO.read(:stdio, :all))            # read STDIN, split into list
|> Enum.map(fn x -> String.to_integer(x) end)  # convert strings to integers
|> Enum.reduce(fn x, acc -> x + acc end)       # add integers together
|> IO.puts                                     # print

julia

sum = 0                            # initialize accumulator
for num in eachline(stdin)         # loop over all input lines
  global sum += parse(Int64, num)  # convert to integer, add to accumulator
end                                # end of for loop
println(sum)                       # output with newline

# alternate method
# read bytes, convert to string, split to vector on newlines
numvec = split(String(read(stdin)), r"\n")
numvec[end] = "0"                    # change ending null string to a zero
println(sum(parse.(Int64, numvec)))  # convert strings to integers, add, print