NAME

dtruss - process syscall details. Uses DTrace.

SYNOPSIS

dtruss [-acdeflhoLs] [-t syscall] { -p PID | -n name | command }

DESCRIPTION

dtruss prints details on process system calls. It is like a DTrace version of truss, and has been designed to be less intrusive than truss.

Of particular interest is the elapsed times and on cpu times, which can identify both system calls that are slow to complete, and those which are consuming CPU cycles.

Since this uses DTrace, only users with root privileges can run this command.

OPTIONS

-a: print all details
-b bufsize: dynamic variable buffer size. Increase this if you notice dynamic variable drop errors. The default is "4m" for 4 megabytes per CPU.
-c: print system call counts
-d: print relative timestamps, us
-e: print elapsed times, us
-f: follow children as they are forked
-l: force printing of pid/lwpid per line
-L: don't print pid/lwpid per line
-n name: examine processes with this name
-W name: wait for a process matching this name
-o: print on-cpu times, us
-s: print stack backtraces
-p PID: examine this PID
-t syscall: examine this syscall only

EXAMPLES

run and examine the "df -h" command: # dtruss df -h
examine PID 1871: # dtruss -p 1871
examine all processes called "tar": # dtruss -n tar
run test.sh and follow children: # dtruss -f test.sh
run the "date" command and print elapsed and on cpu times,: # dtruss -eo date

FIELDS

PID/LWPID: Process ID / Lightweight Process ID
RELATIVE: relative timestamps to the start of the thread, us (microseconds)
ELAPSD: elapsed time for this system call, us
CPU: on-cpu time for this system call, us
SYSCALL(args): system call name, with arguments (some may be evaluated)

DOCUMENTATION

See the DTraceToolkit for further documentation under the Docs directory. The DTraceToolkit docs may include full worked examples with verbose descriptions explaining the output.

EXIT

dtruss will run forever until Ctrl-C is hit, or if a command was executed dtruss will finish when the command ends.

AUTHOR

Brendan Gregg [Sydney, Australia]