// files.groovy — reading and writing files the Groovy way.
def dir = File.createTempDir()
def csv = new File(dir, 'orders.csv')

// Write: text in one go
csv.text = '''id,customer,total
PO-1,Acme,250
PO-2,Globex,90
PO-3,Acme,1200
'''

// Append
csv << 'PO-4,Initech,40\n'

// Read all lines
def lines = csv.readLines()
println "${lines.size() - 1} data rows"                       // 4 data rows

// Read line by line (memory-friendly for big files), skipping the header
def total = 0
csv.eachLine { line, number ->
    if (number == 1) return                                  // header
    def (id, customer, amount) = line.split(',')
    total += amount.toInteger()
}
println "Total: $total"                                      // 1580

// Parse into maps using the header
def header = lines.head().split(',')
def rows = lines.tail().collect { l -> [header, l.split(',')].transpose().collectEntries() }
println rows.findAll { it.customer == 'Acme' }*.id             // [PO-1, PO-3]

// Write with a writer (closes automatically)
def report = new File(dir, 'report.txt')
report.withWriter('UTF-8') { w ->
    rows.groupBy { it.customer }.each { cust, list -> w.writeLine("$cust: ${list.size()} order(s)") }
}
print report.text

// List and clean up files
dir.eachFile { println "file: ${it.name} (${it.length()} bytes)" }
dir.deleteDir()
println "cleaned up: ${!dir.exists()}"