Bash script: split word on each letter

Pure bash solution, no external tools used to process the strings, just parameter expansion:

#! /bin/bash
str='battery.charge: 90 battery.charge.low: 30 battery.runtime: 3690 battery.voltage: 230.0 device.mfr: MGE UPS SYSTEMS device.model: Pulsar Evolution 500'

IFS=: read -a fields <<< "$str"

for (( i=0 ; i < ${#fields[@]} ; i++ )) ; do
    f=${fields[i]}

    notfirst=$(( i>0 ))
    last=$(( i+1 == ${#fields[@]} ))

    (( notfirst )) && echo -n ${f% *}

    start=('' $'\n' ' ')
    colon=('' ': ')
    echo -n "${start[notfirst + last]}${f##* }${colon[!last]}"
done
echo

Explanation: $notfirst and $last are booleans. The part before the last space ${f% *} isn't printed for the first field, as there is no such thing. $start and $colon hold various strings that separate the fields: at the first item, notfirst + last is 0, so nothing is prepended, for the rest of the lines, $notfirst is 1, so a newline is printed, and for the last line, the addition gives 2, so a space is printed. Then, the part after the last space is printed ${f##* }. Colon is printed for all lines except the last one.

You can use the split tool:

split -l 1000 words.txt words-

will split your words.txt file into files with no more than 1000 lines each named

words-aa
words-ab
words-ac
...
words-ba
words-bb
...

If you omit the prefix (words- in the above example), split uses x as the default prefix.

For using the generated files with parallel you can make use of a glob:

split -l 1000 words.txt words-
parallel ./script.sh ::: words-[a-z][a-z]