printf

A `printf` format reference page (cheat sheet)

Summary: This page is a printf formatting cheat sheet. I originally created this cheat sheet for my own purposes, and then thought I would share it here.

A great thing about the printf formatting syntax is that the format specifiers you can use are very similar — if not identical — between different languages, including C, C++, Java, Perl, PHP, Ruby, Scala, and others. This means that your printf knowledge is reusable, which is a good thing.

An example of Scala’s `f` string interpolator

With Scala it’s common to embed variables in strings like this with the s string interpolator:

val name = "Fred"
println(s"My name is $name.")

That’s cool, but when you need to format your string, Scala gives you an even more powerful tool: the f string interpolator. Here’s an example of how I just did this in my LittleLogger logging library:

Scala shell scripts and the command line: Prompting the user, and reading input

A great thing about Scala is that not only is it scalable, it was also created to help you work on small tasks, including being useful in shell scripts. This includes small shell script tasks like prompting a user interactively from a shell script, and reading their input.

You can prompt users with print commands like println and print, and you can read their input with all of these methods that are available on the Scala Console class:

Java String formatting with the String.format method (like ‘sprintf’)

Java String formatting FAQ: How can I format Java String output?

For a long time I appended Java strings together using the + operator to combine them into the output format I wanted, but I always knew that approach was pretty ugly. Fortunately at some point I learned how to use the Java String format method to format my text, and as you’ll see, the resulting code is much cleaner this way.

PHP printing - How to print variables in a PHP string

Nothing major here, just a quick example of how to print variables in PHP, particularly how to print variables in the middle of a PHP string. When you first get started programming in PHP, how to print variables in a PHP string is a common question, so I thought I'd share some examples here.

There are many ways to print variables in a PHP string, but these are some of the most common approaches:

Perl printing examples

Perl printing FAQ: Can you share some Perl printing examples?

There are several different ways to print in Perl, and I thought I'd share some examples here today.

The Perl print function

Generally you'll print simple output with the Perl print function. As a simple example, you can print a string literal using the Perl print function, like this:

Perl printf format examples (reference page)

Here’s a reference page (cheat sheet) of Perl printf formatting options. Hopefully this list covers the most common Perl printf printing options you’ll run into, or will at least point you in the right direction.

Formatting strings

Here are several examples that show how to format strings with Perl and printf. I’ll use single quotes in all my printf examples to help demonstrate left- and right-justification.