EVAL - evaluate arithmetic and logical expressions.

Syntax:

EVAL expression [expression]*

Examples:

eval 3+3 4**2 "xxx"+"yyy"
eval sin( 90.0 / (360.0/(2*pi)))

Description:

EVAL displays the value of each expression, separated by spaces. EVAL expressions take the same form as expressions in the TSS IF command.

An "_" in any expression represents the value of the previous expression. For example,

eval 3+3 _

displays

6 6

As with IF, EVAL keeps the value of "_" in the UST core file for subsequent use by later EVAL or IF commands.

EVAL lets you redirect its output using the normal ">file" and ">>file" constructions. However, to avoid confusion with expressions that use ">" or ">>" as operators, the following rules apply:

A redirection may only appear on the command line as the first argument (after the command name EVAL) or as the last argument. Putting the redirection first is preferred, since this syntax cannot be confused with valid expressions. If a ">name" or ">>name" construct appears elsewhere on the command line, EVAL assumes it is part of an expression.
A redirection construct must have a space before the ">" or ">>". If the redirection is the first argument, it must also have a space after the filename. If there is a space immediately after the ">" or ">>", the construct is assumed to be part of an expression rather than a redirection construct. To be on the safe side, it is a good idea to put a space after ">" or ">>" whenever they are used as operators.
If a construct has the form ">something" or ">>something" and is in the right place on the command line, the construct is assumed to be a redirection. EVAL tries to open "something" as an output file name; if this fails because "something" doesn't have the proper syntax to be a pathname, EVAL then assumes the string was part of an expression after all and attempts to evaluate it as an expression.
If "something" has the syntax of a pathname but there is some other reason why it can't be opened, EVAL terminates with an appropriate error message.

These rules do not avoid all ambiguity. For example, in an expression like

eval 3+5 >4/2

the "4/2" is assumed to be a file named "2" under a userid named "4". This will probably fail unless your site really has a userid named "4". Such situations seldom occur. If you do not want "4/2" to be taken as a filename, put a space after the ">", as in

eval 3+5 > 4/2

EVAL - evaluate arithmetic and logical expressions.

Syntax:

Examples:

Description:

See Also: