A.1 Major Changes Between V7 and SVR3.1

The awk language evolved considerably between the release of Version 7 Unix (1978) and the new version that was first made generally available in System V Release 3.1 (1987). This section summarizes the changes, with cross-references to further details:

• The requirement for `;' to separate rules on a line (see section awk Statements Versus Lines).

• User-defined functions and the return statement (see section User-Defined Functions).

• The delete statement (see section The delete Statement).

• The do-while statement (see section The do-while Statement).

• The built-in functions atan2, cos, sin, rand, and srand (see section 9.1.2 Numeric Functions).

• The built-in functions gsub, sub, and match (see section String Manipulation Functions).

• The built-in functions close and system (see section Input/Output Functions).

• The ARGC, ARGV, FNR, RLENGTH, RSTART, and SUBSEP built-in variables (see section 7.5 Built-in Variables).

• The conditional expression using the ternary operator `?:' (see section Conditional Expressions).

• The exponentiation operator `^' (see section Arithmetic Operators) and its assignment operator form `^=' (see section Assignment Expressions).

• C-compatible operator precedence, which breaks some old awk programs (see section Operator Precedence (How Operators Nest)).

• Regexps as the value of FS (see section Specifying How Fields Are Separated) and as the third argument to the split function (see section String Manipulation Functions).

• Dynamic regexps as operands of the `~' and `!~' operators (see section How to Use Regular Expressions).

• The escape sequences `\b', `\f', and `\r' (see section 3.2 Escape Sequences). (Some vendors have updated their old versions of awk to recognize `\b', `\f', and `\r', but this is not something you can rely on.)

• Redirection of input for the getline function (see section Explicit Input with getline).

• Multiple BEGIN and END rules (see section The BEGIN and END Special Patterns).

• Multidimensional arrays (see section Multidimensional Arrays).