Linux Shell – Simple Backup Script

#!/bin/bash

# If no username is given, use the current user
if [ -z "$1" ]; then
    user=$(whoami)
else
    if [ ! -d "/home/$1" ]; then
        echo "$1 directory does not exist"
        exit 1
    fi
    user=$1
fi

input="/home/$user"
out="/tmp/${user}_backup_$(date +%Y-%m-%d_%H%M%S).tar.gz"

# Count total files in source directory
function count_files {
    find "$1" -type f | wc -l
}

# Count total directories in source
function count_dirs {
    find "$1" -type d | wc -l
}

# Count directories in archive
function archive_dirs {
    tar -tzf "$1" | grep /$ | wc -l
}

# Count files in archive
function archive_files {
    tar -tzf "$1" | grep -v /$ | wc -l
}

# Create archive and suppress error output
tar -czf "$out" "$input" 2> /dev/null

# Gather statistics
src_files=$(count_files "$input")
src_dirs=$(count_dirs "$input")
arc_dirs=$(archive_dirs "$out")
arc_files=$(archive_files "$out")

# Output results
echo "####### $user #######"
echo "$src_files files were added to the archive"
echo "$src_dirs directories were added to the archive"

if [ "$src_files" -eq "$arc_files" ]; then
    echo "$input has been successfully backed up"
    ls -l "$out"
else
    echo "Backup failed"
fi