TRUSS(1)						    BSD General Commands Manual 						  TRUSS(1)

NAME

     truss -- trace system calls

SYNOPSIS

     truss [-facedDS] [-o file] [-s strsize] -p pid
     truss [-facedDS] [-o file] [-s strsize] command [args]

DESCRIPTION

     The truss utility traces the system calls called by the specified process or program.  Output is to the specified output file, or standard
     error by default.	It does this by stopping and restarting the process being monitored via ptrace(2).

     The options are as follows:

     -f      Trace descendants of the original traced process created by fork(2), vfork(2), etc.

     -a      Show the argument strings that are passed in each execve(2) system call.

     -c      Do not display individual system calls.  Instead, before exiting, print a summary containing for each system call: the total system
	     time used, the number of times the call was invoked, and the number of times the call returned with an error.

     -e      Show the environment strings that are passed in each execve(2) system call.

     -d      Include timestamps in the output showing the time elapsed since the trace was started.

     -D      Include timestamps in the output showing the time elapsed since the last recorded event.

     -S      Do not display information about signals received by the process.	(Normally, truss displays signal as well as system call events.)

     -o file
	     Print the output to the specified file instead of standard error.

     -s strsize
	     Display strings using at most strsize characters.	If the buffer is larger, ``...'' will be displayed at the end of the string.  The
	     default strsize is 32.

     -p pid  Follow the process specified by pid instead of a new command.

     command [args]
	     Execute command and trace the system calls of it.	(The -p and command options are mutually exclusive.)

EXAMPLES

     # Follow the system calls used in echoing "hello"
	   $ truss /bin/echo hello
     # Do the same, but put the output into a file
	   $ truss -o /tmp/truss.out /bin/echo hello
     # Follow an already-running process
	   $ truss -p 34

SEE ALSO

     kdump(1), ktrace(1), ptrace(2)

HISTORY

     The truss command was written by Sean Eric Fagan for FreeBSD.  It was modeled after similar commands available for System V Release 4 and
     SunOS.

BSD
								   May 12, 2009 							       BSD