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 (Note: `awk'
Statements Versus Lines.).
* User-defined functions, and the `return' statement (Note:
* The `delete' statement (Note: The `delete' Statement.).
* The `do'-`while' statement (Note: The `do'-`while' Statement.
* The built-in functions `atan2', `cos', `sin', `rand' and `srand'
(Note: Numeric Built-in Functions.).
* The built-in functions `gsub', `sub', and `match' (Note: Built-in
Functions for String Manipulation.).
* The built-in functions `close', and `system' (Note: Built-in
Functions for Input/Output.).
* The `ARGC', `ARGV', `FNR', `RLENGTH', `RSTART', and `SUBSEP'
built-in variables (Note: Built-in Variables.).
* The conditional expression using the ternary operator `?:' (Note:
* The exponentiation operator `^' (*note Arithmetic Operators:
Arithmetic Ops.) and its assignment operator form `^=' (Note:
* C-compatible operator precedence, which breaks some old `awk'
programs (*note Operator Precedence (How Operators Nest):
* Regexps as the value of `FS' (Note: Specifying How Fields are
Separated.), and as the third argument to the
`split' function (Note: Built-in Functions for String
* Dynamic regexps as operands of the `~' and `!~' operators (Note:
How to Use Regular Expressions.).
* The escape sequences `\b', `\f', and `\r' (Note: 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 (Note: Explicit
Input with `getline'.).
* Multiple `BEGIN' and `END' rules (Note: The `BEGIN' and `END'
* Multi-dimensional arrays (*note Multi-dimensional Arrays:
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