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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 array (see Predefined Variables)
• Multiple -f options on the command line (see Command-Line Options)
• The -v option for assigning variables before program execution begins (see Command-Line Options)
• The -- signal for terminating command-line options
• The ‘\a’, ‘\v’, and ‘\x’ escape sequences (see Escape Sequences)
• A defined return value for the srand() built-in function (see Numeric Functions)
• The toupper() and tolower() built-in string functions for case translation (see String-Manipulation Functions)
• A cleaner specification for the ‘%c’ format-control letter in the printf function (see Format-Control Letters)
• The ability to dynamically pass the field width and precision ("%*.*d") in the argument list of printf and sprintf() (see 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 Using Regular Expression Constants)
• Processing of escape sequences inside command-line variable assignments (see Assigning Variables on the Command Line)