Linux in a Nutshell, 6th Edition

Name

if

Synopsis

if (condition)
 statement1
[else
 statement2]

If condition is true, do statement1; otherwise do statement2 in optional else clause. The condition can be an expression using any of the relational operators <, <=, = =, !=, >=, or >, as well as the array membership operator in, and the pattern-matching operators ~ and !~ (e.g., if ($1 ~ /[Aa].*/)). A series of statements must be put within braces. Another if can directly follow an else in order to produce a chain of tests or decisions.