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5.6. Expressions

SystemTap supports a number of operators that use the same general syntax, semantics, and precedence as in C and awk. Arithmetic is performed per C rules for signed integers. If the parser detects division by zero or an overflow, it generates an error. The following subsections list these operators.

5.6.1. Binary numeric operators

* / % + - > > < < & | && ||

5.6.2. Binary string operators

. (string concatenation)

5.6.3. Numeric assignment operators

= *= /= %= += -= > >= < <= &= = |=

5.6.4. String assignment operators

= .=

5.6.5. Unary numeric operators

+ - ! ~ ++ --

5.6.6. Binary numeric or string comparison operators

< > <= >= == !=

5.6.7. Ternary operator

cond ? exp1 : exp2

5.6.8. Grouping operator

( exp )

5.6.9. Function call

General syntax:

fn ([ arg1, arg2, ... ])

5.6.10. $ptr->member

ptr is a kernel pointer available in a probed context.

5.6.11. <value> in <array_name>

This expression evaluates to true if the array contains an element with the specified index.

5.6.12. [ <value>, … ] in <array_name>

The number of index values must match the number of indexes previously specified.