/* -*- scala -*- */

/* hello world */
/* print a simple string on stdout */
println("Hello World")

/* argv */
/* access command line parameters (no segmentation fault accepted, nor silent exception, so some languages must explicitly check the presence of the argument) */
println(args(0))

/* env */
/* access environment variable */
println(System getenv "HOME")

/* test file exists */
/* return exit code error (non zero) if a file does not exist */
if(!new java.io.File("/etc/mtab").exists) exit(1)

/* test file readable */
/* return exit code error (non zero) if a file is not readable */
if(!new java.io.File("/etc/mtab").canRead) exit(1)

/* formatting */
/* print integers in a simple formatted string */
val (a, b) = (1, 2)
println(a + " + " + b + " = " + (a + b))


/* system */
/* call an external program and check the return value */
def exec = Runtime.getRuntime.exec(_:String)

if (exec("false").waitFor > 0)
  error("false failed")

new io.BufferedSource(exec("echo done").getInputStream) foreach print


/* sed in place */
/* remove #-comments from a file (modifying the file, i.e. in place) */
val i = io.Source.fromFile(args(0)).mkString
val w = new java.io.FileWriter(args(0))
w write i.replaceAll("#.*\n","")
w.close


/* compile what must be */
/* find and compile .c files into .o when the .o is old or absent */
for (s <- new java.io.File(args(0)).listFiles if ""+s endsWith ".c") {
  val o = new java.io.File((""+s dropRight 1)+"o")
  if (!o.exists || o.lastModified < s.lastModified) {
    println("compiling "+s+" to "+o)
    Runtime.getRuntime.exec("gcc -c " + s + " -o " + o)
  }
}


/* grep */
/* grep with -F -i -h handling, usage, grep'ing many files */
val options = "-([hiF]+)".r
val (optList, pattern :: files) = args.toList span
   (options.pattern matcher _ matches)
val opts = optList.map{ case options(x) => x }.mkString.toSet

if (args.isEmpty || opts('h')) {
    println("usage: grep [-F] [-i] regexp [files...]")
    exit(1)
}

val mods = Map('i' -> ("(?i)" + _),
               'F' -> (java.util.regex.Pattern.quote(_)))
               .filterKeys(opts)
               .withDefaultValue((x: String) => x)

val regex = mods('i')(mods('F')(pattern)).r

files foreach { file =>
    io.Source fromFile file getLines () foreach { line =>
        regex findFirstIn line foreach { _ =>
            if (files.size > 1) print(file+":")
            println(line)
        }
    }
}