sed & awk, 2nd Edition

Formatted Printing

Many of the scripts that we’ve written so far perform the data processing tasks just fine, but the output has not been formatted properly. That is because there is only so much you can do with the basic print statement. And since one of awk’s most common functions is to produce reports, it is crucial that we be able to format our reports in an orderly fashion. The filesum program performs the arithmetic tasks well but the report lacks an orderly format.

Awk offers an alternative to the print statement, printf, which is borrowed from the C programming language. The printf statement can output a simple string just like the print statement.

awk 'BEGIN { printf ("Hello, world\n") }'

The main difference that you will notice at the outset is that, unlike print, printf does not automatically supply a newline. You must specify it explicitly as “\n”.

The full syntax of the printf statement has two parts:

printf ( format-expression [, arguments] )

The parentheses are optional. The first part is an expression that describes the format specifications; usually this is supplied as a string constant in quotes. The second part is an argument list, such as a list of variable names, that correspond to the format specifications. A format specification is preceded by a percent sign (%) and the specifier is one of the characters shown in Table 7.6. The two main format specifiers are s for strings and d for decimal integers.^[12]

Table 7.6. Format Specifiers Used in printf

Character ...