exshell

#!/usr/bin/env bash
# exshell -- a handy way to use command-line formulae's output to augment a TAB-separated input
#
# Synopsis:
# $ cat a.txt
# USA	United States of America
# India	Republic of India
# South_Korea	Republic of Korea (ROK)
#
# $ exshell <a.txt \
#     'curl -fsSL https://en.wikipedia.org/wiki/"$1" | grep -i "Population" | tail -n +2 | sed "s/<.*$//"' \
#     'curl -fsSL https://en.wikipedia.org/wiki/"$1" | grep -i "Wikidata item" | tr " =" "\n" | grep www.wikidata.org' \
#     | column -t -s$'\t'
# USA          United States of America  325,719,178    "https://www.wikidata.org/wiki/Special:EntityPage/Q30"
# India        Republic of India         1,324,171,354  "https://www.wikidata.org/wiki/Special:EntityPage/Q668"
# South_Korea  Republic of Korea (ROK)   51,446,201     "https://www.wikidata.org/wiki/Special:EntityPage/Q884"
#
# TODO improve example to use more than just $1
##
# Author: Jaeho Shin <[email protected]>
#         Madhav Sharan <[email protected]>
# Created: 2018-09-19
##

# prepare the commands to run for each given formula
cmds=()
for formula; do
    if type "$formula" &>/dev/null || test -x "$formula"; then
        # call formula directly when it's an executable passing the input columns as arguments
        cmd="$formula"
    else # otherwise, treat it as a bash script that uses positional args
        cmd="bash -c $(
            if test ${BASH_VERSINFO[0]} -ge 4
            then echo "${formula@Q}"  # using simpler quotes in bash>=4 when possible
            else printf %q "$formula"
            fi
        ) --"
    fi
    cmds+=("$cmd")
done

# compile each input TAB-separated line into a bash script that emits output of the commands as augmented columns
{
echo "IFS=\$'\\t'"
while read; do
    printf 'a=%q;set -- $a\npaste <(echo "$*")' "$REPLY"
    printf ' <(%s "$@" </dev/null | head -1)' "${cmds[@]}"
    echo
done
} |
# then run the compiled script
bash -s