What is truss or strace?

When you have a problem with your web server it is often quite useful to use a system call tracer to see what the web server is doing. System call tracers exist on most UNIX platforms.

truss

-vall Verbose. Displays the contents of any structures passed by address to all system calls. Input values as well as values returned by the operating system are shown.

-wall Show the contents of the I/O buffer for each write() on all file descriptors

-o output file

-p process id to trace

Replace -p [pid] with [command] to trace a specific command.

To truss ZWS upon startup you should invoke this command

truss -fae -vall -rall -wall -o /tmp/truss.log ./path/to/zeus/ -z

strace

The equivalent strace command would be :-

strace -fe verbose=all -e write=all -o /tmp/strace.log -p [pid]

-f traces all child processes as they are created byt he currently traced process as a result of the fork() system call.

-e is a qualifying expression which modifies which events to trace or how to race them

verbose=all dereferences structures for all system calls

write=all performs a full hexadecimal and ASCII dump of all the data written to all file descriptors

-o output file

-p process id to trace

Replace -p [pid] with [command] to trace a specific command.

tusc

Using tusc, would yield :-

tusc -fae -o /tmp/tusc.log -p [pid]

-f follows forks

-a prints exec arguements

-e prints environment variables

-o output file

-p process id to trace

Replace -p [pid] with [command] to trace a specific command.

ktrace

On FreeBSD, BSDI and Open BSD, use ktrace :-

ktrace -di -ta -f /tmp/ktrace.log -p [pid]

-d follows decendants

-i passess trace flags on to all future children of the designated processes

-ta traces all points

-f redirects output to specified file, rather than the default

-p process id to trace

Replace -p [pid] with [command] to trace a specific command.

The output of ktrace is not human readable. Use kdump to decode it.

trace

trace is the system tracing program on Tru64

Usage: trace -fPp [pid]

-f follows fork()ed child processes

-P prints process id of process being traced before each system call

-p process id to be traced

Replace -p [pid] with [command] to trace a specific command.

par

Use par on Irix to trace.

Usage: par -s -SS -o /tmp/trace.log -p [pid]

-s collects system call and signal data for the process being traced

-SS prints detailed system call trace and summary of system calls and signal counts

-o file in which raw output data is written

-p process id to be traced

Replace -p [pid] with [command] to trace a specific command.

Content Manager [Administrator] 19 September 2005