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TRUSS(1)		FreeBSD	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 moni-
     tored 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) sys-
	     tem 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 num-
	     ber 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.

FreeBSD	10.1			 May 12, 2009			  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | HISTORY

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