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Oracle® Solaris 11.4 DTrace (Dynamic Tracing) Guide

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Updated: September 2020
 
 

Macro Variables

The D compiler defines a set of built-in macro variables that you can use when writing D programs or interpreter files. Macro variables are identifiers that are prefixed with a dollar sign ($) and are expanded once by the D compiler when processing your input file. The D compiler provides the following macro variables:

Table 18  D Macro Variables
D Macro Variables
Description
Reference
$[0-9]+
macro arguments
$egid
effective group-ID
$euid
effective user-ID
$gid
real group-ID
$pid
process ID
$pgid
process group ID
$ppid
parent process ID
$projid
project ID
$sid
session ID
$target
target process ID
$taskid
task ID
$uid
real user-ID

Except for the $[0-9]+ macro arguments and the $target macro variable, the macro variables all expand to integers corresponding to system attributes such as the process ID and user ID. The variables expand to the attribute value associated with the current dtrace process itself, or whatever process is running the D compiler.

Using macro variables in interpreter files enables you to create persistent D programs that do not need to be edited each time you use the programs. For example, to count all system calls except those executed by the dtrace command, you can use the following D program clause containing $pid:

syscall:::entry
/pid != $pid/
{
        @calls = count();
}

This clause always produces the desired result, even though each invocation of the dtrace command will have a different process ID. Macro variables can be used anywhere an integer, identifier, or string can be used in a D program.

Macro variables are expanded only once (that is, not recursively) when the input file is parsed. Each macro variable is expanded to form a separate input token, and cannot be concatenated with other text to yield a single token. For example:

123$pid

If $pid expands to the value 456, the D code would expand to the two adjacent tokens 123 and 456, resulting in a syntax error, rather than the single integer token 123456.

Macro variables are expanded and concatenated with adjacent text inside of D probe descriptions at the start of your program clauses. For example, the following clause uses the DTrace pid provider to instrument the dtrace command:

pid$pid:libc.so:printf:entry
{
        ...
}

Macro variables are only expanded once within each probe description field; they may not contain probe description delimiters (:).