Node:V7/SVR3.1, Next:SVR4, Previous:Language History, Up:Language History

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 awk Statements Versus Lines).
• User-defined functions and the return statement (see User-Defined Functions).
• The delete statement (see The delete Statement).
• The do-while statement (see The do-while Statement).
• The built-in functions atan2, cos, sin, rand, and srand (see Numeric Functions).
• The built-in functions gsub, sub, and match (see String Manipulation Functions).
• The built-in functions close and system (see Input/Output 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 Expressions).
• The exponentiation operator ^ (see Arithmetic Operators) and its assignment operator form ^= (see Assignment Expressions).
• C-compatible operator precedence, which breaks some old awk programs (see Operator Precedence (How Operators Nest)).
• Regexps as the value of FS (see Specifying How Fields Are Separated) and as the third argument to the split function (see String Manipulation Functions).
• Dynamic regexps as operands of the ~ and !~ operators (see How to Use Regular Expressions).
• 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 Explicit Input with getline).
• Multiple BEGIN and END rules (see The BEGIN and END Special Patterns).
• Multidimensional arrays (see Multidimensional Arrays).