Major Changes between V7 and SVR3.1

The awk language evolved considerably between the release of Version 7 Unix (1978) and the new version 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 Numeric Built-in Functions).
• The built-in functions gsub, sub, and match (see section Built-in Functions for String Manipulation).
• The built-in functions close, and system (see section Built-in Functions for Input/Output).
• The ARGC, ARGV, FNR, RLENGTH, RSTART, and SUBSEP built-in variables (see section 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 Built-in Functions for String Manipulation).
• Dynamic regexps as operands of the `~' and `!~' operators (see section How to Use Regular Expressions).
• The escape sequences `\b', `\f', and `\r' (see section Escape Sequences). (Some vendors have updated their old versions of awk to recognize `\r', `\b', and `\f', 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).
• Multi-dimensional arrays (see section Multi-dimensional Arrays).

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