FreeBSD Man Pages

truss(1)

SYNOPSIS

     truss [-faedDS] [-o file] -p pid
     truss [-faedDS] [-o file] 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 procfs(5).

     The options are as follows:

     -f      Trace decendants 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.

     -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.

     -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 1

SEE ALSO

     kdump(1), ktrace(1), procfs(5)

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.

SPONSORED LINKS