strace(1M)

strace -- print STREAMS trace messages

Synopsis

strace [mid sid level] ...

Description

strace without arguments writes all STREAMS event trace messages from all drivers and modules to its standard output. These messages are obtained from the STREAMS log driver (see log(7)). If arguments are provided they must be in triplets of the form:

mid, sid, level

where mid is a STREAMS module ID number, sid is a sub-ID number, and level is a tracing priority level. Each triplet indicates that tracing messages are to be received from the given module/driver, sub-ID (usually indicating minor device), and priority level equal to or less than the given level. The token ``all'' may be used for any member to indicate no restriction for that attribute.

The format of each trace message output is:

   <seq> <time> <ticks> <level> <flags> <mid> <sid> <text>

seq

trace sequence number

time

time of message in hh:mm:ss

ticks

time of message in machine ticks since boot

level

tracing priority level

flags

E: message is also in the error log
F: indicates a fatal error
N: mail was sent to the system administrator

mid

module ID number of source

sid

sub-ID number of source

text

formatted text of the trace message

Once initiated, strace will continue to execute until terminated by the user.

References

log(7)

Notices

Due to performance considerations, only one strace process is permitted to open the STREAMS log driver at a time. The log driver has a list of the triplets specified in the command invocation, and compares each potential trace message against this list to decide if it should be formatted and sent up to the strace process. Hence, long lists of triplets will have a greater impact on overall STREAMS performance. Running strace will have the most impact on the timing of the modules and drivers generating the trace messages that are sent to the strace process. If trace messages are generated faster than the strace process can handle them, then some of the messages will be lost. This last case can be determined by examining the sequence numbers on the trace messages output.

Examples

Output all trace messages from the module or driver whose module ID is 41:

strace 41 all all

Output those trace messages from driver/module ID 41 with sub-IDs 0, 1, or 2:

strace 41 0 1 41 1 1 41 2 0

Messages from sub-IDs 0 and 1 must have a tracing level less than or equal to 1. Those from sub-ID 2 must have a tracing level of 0.