Simple Report

Numbers and Strings

AWK is a very small language and only has a few basic data types. In this lession we'll go over numbers and strings.

Numbers

Numbers in AWK are implemented as double-precision floating point numbers. There is no distinction between integers, floats and doubles.

AWK understands octal number constants (starting with 0) and hexadecimal number constants (starting with 0x or 0X).

Numeric operations

You can use the standard arithmetic operators +, -, *, /, %. The exponentiation operator is ^. There are some builtin numeric functions, including trigonometric functions, random number generation, and int(x) to truncate a number to the nearest integer between x and zero.

Strings

AWK strings are sequences of characters. Specify a string constant using double quotes.

String operations

There is only one string operation: concatenation. Concatenation does not have a special operator; simply placing two strings next to each other concatenates them:

BEGIN {
    hw = "Hello" "World"
    print hw
}
# => HelloWorld

AWK has a wealth of string manipulation functions. We will be introduced to them in depth as we proceed through the track.

Converting between numbers and strings

There are no explicit operators to convert between numbers and strings. AWK will do this implicitly based on the context of the program. This makes working with input field values very simple: AWK generally just does what you want it to do.

• print x + y will convert the values of the x and y variables to numbers thanks to the + numeric operation.
• print x y will convert the values of the x and y variables to strings thanks to the concatenation operation.

If you want to be explicit about it, 0 + x gives the number representation of x and "" x gives the string representation of x.

From strings to numbers

The manner that AWK converts a string to a number can be confusing. A simple way to think of it is that AWK reads "number characters" from the start of a string until it finds a "non-number" character. Some examples are:

• "2.5" converts to the number 2.5;
• "1e3" converts to the number 1000 (scientific notation);
• "456abc" converts to the number 456 (because a is not a "numeral", conversion stops there).
• "abc789" converts to the number 0 (there are no numbers at the start of the string).