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HP-UX 11i Version 3: February 2007

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strace — write STREAMS event trace messages to standard output


strace [ mod sub pri ] ...


strace gets STREAMS event trace messages from STREAMS drivers and modules via the STREAMS log driver (strlog(7)), and writes these messages to standard output. By default, strace without arguments writes all STREAMS trace messages from all drivers and modules. strace with command-line arguments limits the trace messages received.

The arguments, which must be specified in groups of three, are:


Specifies the STREAMS module identification number from the streamtab entry.


Specifies a subidentification number (often corresponding to a minor device).


Specifies a tracing priority level. strace gets messages of a level equal to or less than the value specified by pri. Only positive integer values are allowed.

The value all can be used for any argument in the strace command line to indicate that there are no restrictions for that argument.

Multiple sets of the three arguments can be specified to obtain the messages from more than one driver or module.

Only one strace process can open the STREAMS log driver at a time.

When strace is invoked, the log driver compares the sets of command line arguments with actual trace messages, returning only messages that satisfy the specified criteria.

STREAMS event trace messages have the following format:

seq time tick pri ind mod sub text

Components are interpreted as follows:


Trace event sequence number.


Time the message was sent expressed in hh:mm:ss.


Time the message was sent expressed in machine ticks since the last boot.


Tracing priority level as defined by the STREAMS driver or module that originates the messages.


Can be any combination of the following three message indicators:


The message has also been saved in the error log.


The message signaled a fatal error.


The message has also been mailed to the system administrator.


Module identification number of the trace message source.


Subidentification number of the trace message source.


Trace message text.

strace runs until terminated by the user.


Display all trace messages received from the driver or module identified by mod 28:

strace 28 all all

Display trace messages of any tracing priority level from the driver or module identified by mod 28 and its minor devices identified by the sub 2, 3, or 4:

strace 28 2 all 28 3 all 28 4 all

Display the trace messages from the same driver or module and subs but limit the priority levels to 0 for subs 2 and 3; 1 for sub 4, driver or module 28:

strace 28 2 0 28 3 0 28 4 1


Running strace with several sets of arguments can impair STREAMS performance, particularly for those modules and drivers that are sending the messages.

Also be aware that strace may not be able to handle a large number of messages. If drivers and modules return messages to strace too quickly, some may be lost.



NLS catalog for strace.

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