NAME    [Toc]    [Back]

     ktrace - process tracing

SYNOPSIS    [Toc]    [Back]

     #include <sys/types.h>
     #include <sys/param.h>
     #include <sys/uio.h>
     #include <sys/ktrace.h>

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

DESCRIPTION    [Toc]    [Back]

     The  ktrace() function enables or disables tracing of one or
more processes.
  Users may only trace their own processes.  Only the superuser can
     trace setuid or setgid programs.

     tracefile  gives  the  pathname  of  the file to be used for
tracing.  The
     file must exist, be writable by the calling process, and not
be a symbolic
 link.  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 specified
 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 generate
 much output).
           KTRFAC_PSIG          Trace posted signals.
           KTRFAC_EMUL          Trace emulation changes.
           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    [Toc]    [Back]

     On successful completion a value of 0 is  returned.   Otherwise, a value of
     -1 is returned and errno is set to show the error.

ERRORS    [Toc]    [Back]

     ktrace() will fail if:

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

     [EINVAL]        The pathname contains a character  with  the
high-order bit
                     set.

     [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  or  the  path  refers  to a symbolic
link.

     [ELOOP]         Too many symbolic links were encountered  in
translating
                     the pathname.

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

SEE ALSO    [Toc]    [Back]

     kdump(1), ktrace(1)

HISTORY    [Toc]    [Back]

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

OpenBSD      3.6                           June      4,      1993