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KTRACE(2)		  FreeBSD System Calls Manual		     KTRACE(2)

NAME
     ktrace -- process tracing

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <sys/param.h>
     #include <sys/time.h>
     #include <sys/uio.h>
     #include <sys/ktrace.h>

     int
     ktrace(const char *tracefile, int ops, int	trpoints, int pid);

DESCRIPTION
     The ktrace() function enables or disables tracing of one or more pro-
     cesses.  Users may	only trace their own processes.	 Only the super-user
     can trace setuid or setgid	programs.

     The tracefile gives the pathname of the file to be	used for tracing.  The
     file must exist and be a regular file writable by the calling process.
     All trace records are always appended to the file,	so the file must be
     truncated to zero length to discard previous trace	data.  If tracing
     points are	being disabled (see KTROP_CLEAR	below),	tracefile may be NULL.

     The ops parameter specifies the requested ktrace operation.  The defined
     operations	are:

	   KTROP_SET		 Enable	trace points specified in trpoints.
	   KTROP_CLEAR		 Disable trace points specified	in trpoints.
	   KTROP_CLEARFILE	 Stop all tracing.
	   KTRFLAG_DESCEND	 The tracing change should apply to the	speci-
				 fied process and all its current children.

     The trpoints parameter specifies the trace	points of interest.  The
     defined trace points are:

	   KTRFAC_SYSCALL	Trace system calls.
	   KTRFAC_SYSRET	Trace return values from system	calls.
	   KTRFAC_NAMEI		Trace name lookup operations.
	   KTRFAC_GENIO		Trace all I/O (note that this option can gen-
				erate much output).
	   KTRFAC_PSIG		Trace posted signals.
	   KTRFAC_CSW		Trace context switch points.
	   KTRFAC_INHERIT	Inherit	tracing	to future children.

     Each tracing event	outputs	a record composed of a generic header followed
     by	a trace	point specific structure.  The generic header is:

     struct ktr_header {
	     int     ktr_len;		     /*	length of buf */
	     short   ktr_type;		     /*	trace record type */
	     pid_t   ktr_pid;		     /*	process	id */
	     char    ktr_comm[MAXCOMLEN+1];  /*	command	name */
	     struct  timeval ktr_time;	     /*	timestamp */
	     caddr_t ktr_buf;
     };

     The ktr_len field specifies the length of the ktr_type data that follows
     this header.  The ktr_pid and ktr_comm fields specify the process and
     command generating	the record.  The ktr_time field	gives the time (with
     microsecond resolution) that the record was generated.  The ktr_buf is an
     internal kernel pointer and is not	useful.

     The generic header	is followed by ktr_len bytes of	a ktr_type record.
     The type specific records are defined in the <sys/ktrace.h> include file.

RETURN VALUES
     The ktrace() function returns the value 0 if successful; otherwise	the
     value -1 is returned and the global variable errno	is set to indicate the
     error.

ERRORS
     Ktrace() will fail	if:

     [ENOTDIR]		A component of the path	prefix is not a	directory.

     [ENAMETOOLONG]	A component of a pathname exceeded 255 characters, or
			an entire path name exceeded 1023 characters.

     [ENOENT]		The named tracefile does not exist.

     [EACCES]		Search permission is denied for	a component of the
			path prefix.

     [ELOOP]		Too many symbolic links	were encountered in translat-
			ing the	pathname.

     [EIO]		An I/O error occurred while reading from or writing to
			the file system.

     [ENOSYS]		The kernel was not compiled with ktrace	support.

SEE ALSO
     kdump(1), ktrace(1)

HISTORY
     A ktrace()	function call first appeared in	4.4BSD.

FreeBSD	9.2			 June 4, 1993			   FreeBSD 9.2

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | HISTORY

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