Modifying Options

Options may be set in a D script by using #pragma D followed by the string option and the option name. If the option takes a value, the option name should be followed by an equals sign (=) and the option value. The following examples are all valid option settings:

#pragma D option nspec=4
#pragma D option grabanon
#pragma D option bufsize=2g
#pragma D option switchrate=10hz
#pragma D option aggrate=100us
#pragma D option bufresize=manual

The dtrace(1M) command also accepts option settings on the command-line as an argument to the -x option. For example:

# dtrace -x nspec=4 -x grabanon -x bufsize=2g \
    -x switchrate=10hz -x aggrate=100us -x bufresize=manual

If an invalid option is specified, dtrace indicates that the option name is invalid and exits:

# dtrace -x wombats=25
dtrace: failed to set option -x wombats: Invalid option name
#

Similarly, if an option value is not valid for the given option, dtrace will indicate that the value is invalid:

# dtrace -x bufsize=100wombats
dtrace: failed to set option -x bufsize: Invalid value for specified option
#

If an option is set more than once, subsequent settings overwrite earlier settings. Some options, such as grabanon, may only be set. The presence of such an option sets it, and you cannot subsequently unset it.

Options that are set for an anonymous enabling will be honored by the DTrace consumer that claims the anonymous state. See Chapter 36, Anonymous Tracing for information about enabling anonymous tracing.