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TRUSS(1) BSD General Commands Manual TRUSS(1)
truss -- trace system calls
truss [-facedDS] [-o file] [-s strsize] -p pid
truss [-facedDS] [-o file] [-s strsize] command [args]
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
-D Include timestamps in the output showing the time elapsed since the last recorded
-S Do not display information about signals received by the process. (Normally, truss
displays signal as well as system call events.)
Print the output to the specified file instead of standard error.
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.
Execute command and trace the system calls of it. (The -p and command options are
# 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
kdump(1), ktrace(1), ptrace(2)
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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