A set of functional-ish highlevel functions implemented in bash.

highlevel_func.sh

#!/bin/bash

# A collection of high-level-ish functions for
# bash pipeline operations.

# breakdown the output of ls or find into one
# item per line in STDOUT for pipeline.
#
# Usage:
#     ls . | breakdown
breakdown() {
        local IFS=$(echo -en "\n\b")

        # argument 2 is set
        # read from DATA
        for f in $1; do
                echo "$f"
        done
}

# map the STDOUT from CLI tools like ls or find
# to execute action on each result.
#
# Usage:
#    some-stdout-operation | map <FUNCNAME or CLI COMMAND>
map() {
        local ACTION="$1"
        while read -r INPUT; do
                $ACTION $INPUT
        done
}

# filter the STDOUT from CLI tools like ls or find
# to check all items if matches the testing function or cli tools.
#
# If pass, the item will be echo to STDOUT.
#
# Usage:
#    some-stdout-operation | filter <FUNCNAME or CLI COMMAND>
filter() {
        local TEST="$1"
        while read -r INPUT; do
                if $TEST "$INPUT"; then
                        echo "$INPUT"
                fi
        done
}

# accumulate the STDOUT of FUNC or CLI tools with the
# STDOUT of pipeline to for ACC then echo.
#
# Usage:
#    some-stdout-operation | reduce <FUNCNAME or CLI COMMAND>
reduce() {
        local OP="$1"

        # initialize ACC from first input or argument 2
        if [ ! -z ${2+x} ]; then
                local ACC="$2"
        else
                read -r INPUT
                local ACC="$INPUT"
        fi

        # read from STDIN
        while read -r INPUT; do
                ACC=$($OP "$ACC" "$INPUT")
        done
        echo $ACC
}

# export functions
export -f breakdown
export -f map
export -f filter
export -f reduce

usage_examples.sh

#!/bin/bash

source highlevel_func.sh

hello () {
        echo "hello $1"
}

isdir() {
        if [ -d "$1" ]; then
                return
        fi
        false
}

concat2() {
        echo "$1; $2"
}

# Usage: simple mapping
find ./temp -mindepth 1 | map hello

# Usage: filter find outputs
find ./temp -mindepth 1 | filter isdir | reduce concat2

# Usage: breakdown find / ls output for use
breakdown "$(find ./temp -mindepth 1)" | map hello

# Usage: advanced filter, map and sort
find ./temp -mindepth 1 | filter isdir | map hello | sort -r