file

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.)

Linux/Unix FAQ: Can you share some find command examples?

Sure. The Unix/Linux find command is very powerful. It can search the entire filesystem to find files and directories according to the search criteria you specify. Besides using the find command to locate files, you can also execute other Linux commands (grep, mv, rm, etc.) on the files and directories you find, which makes find extremely powerful. 

Here's a shell script that I use that search Java jar files for any type of pattern. You can use it to search for the name of a class, the name of a package, or any other string/pattern that will show up if you manually ran jar tvf on each jar file. The advantage of this script -- if you're a Unix, Linux, or Cygwin user -- is that this script will search through all jar files in the current directory.

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:

MySQL database FAQ: How do I restore a MySQL backup? (Also written as, "How do I restore a MySQL database dump?")