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 Statements/Lines).
• User-defined functions and the return statement (see User-defined).
• The delete statement (see Delete).
• The do-while statement (see Do Statement).
• The built-in functions atan2, cos, sin, rand, and srand (see Numeric Functions).
• The built-in functions gsub, sub, and match (see String Functions).
• The built-in functions close and system (see I/O Functions).
• The ARGC, ARGV, FNR, RLENGTH, RSTART, and SUBSEP built-in variables (see Built-in Variables).
• The conditional expression using the ternary operator `?:' (see Conditional Exp).
• The exponentiation operator `^' (see Arithmetic Ops) and its assignment operator form `^=' (see Assignment Ops).
• C-compatible operator precedence, which breaks some old awk programs (see Precedence).
• Regexps as the value of FS (see Field Separators) and as the third argument to the split function (see String Functions).
• Dynamic regexps as operands of the `~' and `!~' operators (see Regexp Usage).
• The escape sequences `\b', `\f', and `\r' (see 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 Getline).
• Multiple BEGIN and END rules (see BEGIN/END).
• Multidimensional arrays (see Multi-dimensional).