13.2.5 Positional Parameters

Normally radtest stops parsing its command line when it encounters either first non-optional argument (i.e. the one not starting with dash), or an argument consisting of two dashes. The rest of the command line starting from the first non-optional argument forms positional parameters. These parameters are said to form the top-level environment.

Similarly, when invoking a user-defined function (see section 13.2.7 Function Definitions), arguments passed to it are said to form the current environment of the function. These arguments are positional parameters for this function.

Positional parameters are assigned numbers starting from 1. To access (dereference) a positional parameter, the syntax $n is used, where n is the number of the parameter. Alternative forms, such as ${n} or ${n:-text}, can also be used. These work exactly as described in 13.2.4.3 Dereferencing Variables).

The number of positional parameters can be accessed using a special notation $#.

Several things need to be mentioned:

• All top-level positional parameters have string data type, whereas the types of positional parameters in a function current environment are determined before inoking the function.

• Special notion $0 returns the name of the function being evaluated. When used in the top-level environment, it returns the name of radtest program as given by `--file' (`-f') option.

• Dereferencing non-existing parameter returns empty string. This differs from dereferencing non-existing variable, which results in error.

• AWK programmers should note that assignments (see section 13.2.4.5 Assignment Options) are not included in the top level environment (see example below).

For example, suppose you run:

radtest -f script.rad name foo=bar 5

Then, the top-level environment of program `script.rad' consists of the following variables:

$0 => script.rad $1 => name $2 => 5