A.2 Changes Between SVR3.1 and SVR4

The System V Release 4 (1989) version of Unix awk added these features (some of which originated in gawk):

• The ENVIRON variable (see section 7.5 Built-in Variables).

• Multiple `-f' options on the command line (see section Command-Line Options).

• The `-v' option for assigning variables before program execution begins (see section Command-Line Options).

• The `--' option for terminating command-line options.

• The `\a', `\v', and `\x' escape sequences (see section 3.2 Escape Sequences).

• A defined return value for the srand built-in function (see section 9.1.2 Numeric Functions).

• The toupper and tolower built-in string functions for case translation (see section String Manipulation Functions).

• A cleaner specification for the `%c' format-control letter in the printf function (see section Format-Control Letters).

• The ability to dynamically pass the field width and precision ("%*.*d") in the argument list of the printf function (see section Format-Control Letters).

• The use of regexp constants, such as /foo/, as expressions, where they are equivalent to using the matching operator, as in `$0 ~ /foo/' (see section Using Regular Expression Constants).

• Processing of escape sequences inside command-line variable assignments (see section Assigning Variables on the Command Line).