Count number of lines of a file or all files on a folder

countlines.sh

#!/usr/bin/env bash

function count_lines {
    local file="$1"
    local lines=$(wc -l < "$file")
    echo "$lines"
}

function count_lines_recursive {
    local dir="$1"
    local count=0
    for file in "$dir"/*; do
        if [[ -d "$file" ]]; then
            count=$((count + $(count_lines_recursive "$file")))
        elif [[ -f "$file" ]]; then
            count=$((count + $(count_lines "$file")))
        fi
    done
    echo "$count"
}

if [[ $# -ne 1 ]]; then
    echo "Usage: $0 <file or directory>"
    exit 1
fi

file_or_dir="$1"
if [[ -d "$file_or_dir" ]]; then
    count=$(count_lines_recursive "$file_or_dir")
    echo "Total number of lines in $file_or_dir: $count"
elif [[ -f "$file_or_dir" ]]; then
    count=$(count_lines "$file_or_dir")
    echo "Number of lines in $file_or_dir: $count"
else
    echo "Error: $file_or_dir is not a file or directory"
    exit 1
fi