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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.  Out-
     put 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
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