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 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 predefined variables (see section Predefined Variables)
• Assignable $0 (see section Changing the Contents of a Field)
• The conditional expression using the ternary operator ‘?:’ (see section Conditional Expressions)
• The expression ‘indx in array’ outside of for statements (see section Referring to an Array Element)
• 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), rather than using only the first character of FS
• Dynamic regexps as operands of the ‘~’ and ‘!~’ operators (see section Using Dynamic Regexps)
• The escape sequences ‘\b’, ‘\f’, and ‘\r’ (see section Escape Sequences)
• 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)