KTRACE(2) BSD System Calls Manual KTRACE(2)NAME
ktrace — process tracing
SYNOPSIS
#include <sys/types.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 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
On successful completion a value of 0 is returned. Otherwise, a value of
-1 is returned and errno is set to show the error.
ERRORSKtrace() 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.
[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 ALSOktrace(1), kdump(1)HISTORY
A ktrace function call first appeared in 4.4BSD.
4th Berkeley Distribution June 4, 1993 4th Berkeley Distribution
