read

Out of curiosity about Scala’s file-reading performance, I decided to write a “line count” program in Scala. One obvious approach was to count the newline characters in the file:

// took 101 secs (10M lines)
// work on one character at a time
def countLines1(source: Source): Long = {
  var newlineCount = 0L
  for {
    c <- source
    if c.toByte == NEWLINE
  } newlineCount += 1
  newlineCount
}

As the comment shows, this took 101 seconds to read a file that has 10M lines. (An Apache access log file for this website.)

Scala file FAQ: How do I open and read files in Scala?

When you're writing Scala scripts, you often want to read text files. Fortunately it's pretty easy to open and read from a file in Scala. You can just use an approach like this:

Perl write to file FAQ: Can you demonstrate an example of how to write to a file in Perl?

Somehow I managed to go all these years without showing a simple Perl "write to file" example. Let's fix that.

Perl "write to file" example

Here's a short snippet of code that shows how to write to a file in Perl:

SQLite script FAQ: How do I read/execute a "create tables" script from the SQLite command line? (How do I read or execute commands in a file from the sqlite3 command line?)

Many times when you're working with a database, you'll keep all your "create table" commands in a database script, which you'll then execute from your database server command line prompt. The file of database commands you execute is often referred to as a "script", or in this case, a "SQLite script".

Java file utilities FAQ: Do you have any Java file utilities you can share?

As I was working on another Java/Swing application this weekend, I ran across my "Java file utilities" class, and I thought I'd share that class here today. It's nothing too major, but it does include Java methods that let you open, read, write, and copy files using Java.