path: root/static/freebsd/man1/dwatch.1

.\" Copyright (c) 2014-2018 Devin Teske
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.Dd April 18, 2025
.Dt DWATCH 1
.Os
.Sh NAME
.Nm dwatch
.Nd watch processes as they trigger a particular DTrace probe
.Sh SYNOPSIS
.Nm
.Op Fl 1defFmnPqRvVwxy
.Op Fl B Ar num
.Op Fl E Ar code
.Op Fl g Ar group
.Op Fl j Ar jail
.Op Fl k Ar name
.Op Fl K Ar num
.Op Fl N Ar count
.Op Fl o Ar file
.Op Fl O Ar cmd
.Op Fl p Ar pid
.Op Fl r Ar regex
.Op Fl t Ar test
.Op Fl T Ar time
.Op Fl u Ar user
.Op Fl X Ar profile
.Op Fl z Ar regex
.Op Fl -
.Op probe[,...]
.Op args ...
.Nm
.Fl l
.Op Fl fmnPqy
.Op Fl r Ar regex
.Op probe ...
.Nm
.Fl Q
.Op Fl 1qy
.Op Fl r Ar regex
.Sh DESCRIPTION
The
.Nm
utility uses
.Xr dtrace 1
to display process info when a given DTrace probe point is triggered.
Only the root user or users with
.Xr sudo 8 Pq Pa ports/security/sudo
access can run this command.
.Pp
.Nm
automates the process of generating DTrace scripts to coalesce trace output by
date/time,
process info,
and
.Op optionally
probe-specific data.
.Pp
Output format without options is:
.Pp
.Dl date/time uid.gid execname[pid]: psargs
.Pp
For example,
the command
.Ql dwatch BEGIN
produces:
.Pp
.Dl INFO Watching 'dtrace:::BEGIN' ...
.Dl 2017 May 29 08:23:20 0.0 dtrace[60671]: dtrace -s /dev/stdin
.Pp
The
.Fl F
option causes
.Nm
to instead coalesce trace output by date/time,
process info,
and probe traversal.
.Pp
Output format with the
.Ql Fl F
option is:
.Pp
.Dl date/time uid.gid execname[pid]: {->,<-, |} prov:mod:func:name ...
.Pp
For example,
the command
.Ql dwatch -F BEGIN
produces:
.Pp
.Dl INFO Watching 'dtrace:::BEGIN' ...
.Dl 2017 May 29 21:34:41 0.0 dtrace[86593]:  | dtrace:::BEGIN ...
.Pp
The
.Fl R
option causes
.Nm
to display a process tree containing the parent,
grandparent,
and ancestor process info.
.Pp
Output format with the
.Ql Fl R
option is:
.Pp
.Dl date/time uid0.gid0 execname[pid0]: psargs0
.Dl " -+= pid3 uid3.gid3 psargs3"
.Dl "  \e\\-+= pid2 uid2.gid2 psargs2"
.Dl "    \e\\-+= pid1 uid1.gid1 psargs1"
.Dl "      \e\\-+= pid0 uid0.guid0 psargs0"
.Pp
For example,
the command
.Ql dwatch -R BEGIN
produces:
.Pp
.Dl INFO Watching 'dtrace:::BEGIN' ...
.Dl 2017 May 29 21:38:54 0.0 dtrace[86899]: dtrace -s /dev/stdin
.Dl " -+= 86855 604.604 -bash"
.Dl "  \e\\-+= 86857 604.604 /bin/sh /usr/sbin/dwatch -R BEGIN"
.Dl "    \e\\-+= 86897 0.0 sudo dtrace -s /dev/stdin"
.Dl "      \e\\-+= 86899 0.0 dtrace -s /dev/stdin"
.Pp
Of particular interest is the ability to filter using regular expressions.
The
.Ql Fl g Ar group ,
.Ql Fl p Ar pid ,
.Ql Fl r Ar regex ,
.Ql Fl u Ar user ,
and
.Ql Fl z Ar regex
options can be combined with
.Ql Fl R
to match on parent process criteria as well as current process info.
.Pp
In contrast,
the
.Ql Fl j Ar jail ,
and
.Ql Fl k Ar name
options apply only to the current process even if
.Ql Fl R
is given.
.Pp
The
.Ql Fl E Ar code
option gives the ability to customize probe-specific data.
For example,
the command:
.Pp
.Dl dwatch -E 'printf("%s", copyinstr(arg0))' chdir
.Pp
displays the path argument sent to
.Xr chdir 2
calls.
.Pp
Profiles can be written for more complex routines and/or convenience.
To list available profiles use the
.Ql Fl Q
option.
Use the
.Ql Fl X Ar profile
option to use a particular profile.
.Pp
For example,
the command
.Ql dwatch -X kill
displays arguments sent to
.Xr kill 2 .
.Sh OPTIONS
If a
.Ar probe
argument does not contain colon
.Pq Qo Li ":" Qc
and none of
.Ql Fl P ,
.Ql Fl m ,
.Ql Fl f ,
or
.Ql Fl n
are given,
the probe argument is intelligently mapped to its most-likely value.
Use
.Ql Nm Fl l Ar name
to see what probes will match a given name.
.Pp
Multiple probes must be given as a single
.Pq quoted
argument,
separated by comma and/or whitespace.
Any/all arguments following said probes will be passed to
.Xr dtrace 1
unmodified.
.Bl -tag -width "-c count"
.It Fl 1
Print one line per process/profile
.Pq Default; disables Ql Fl R .
.It Fl B Ar num
Maximum number of arguments to display
.Pq Default 64 .
.It Fl d
Debug.
Send
.Xr dtrace 1
script to stdout instead of executing.
.It Fl e
Exit after compiling request but prior to enabling probes.
.It Fl E Ar code
DTrace
.Ar code
for event details.
If `-',
read from stdin.
This allows customization of what is printed after date/time and process info.
By default,
the name and arguments of the program triggering the probe are shown.
Can be specified multiple times.
.It Fl f
Enable probes matching the specified function names.
.It Fl F
Coalesce trace output by probe.
.It Fl g Ar group
Group filter.
Only show processes matching
.Ar group
name/gid.
This can be an
.Xr awk 1
regular expression to match a numerical gid.
.It Fl j Ar jail
Jail filter.
Only show processes matching
.Ar jail
name/jid.
.It Fl k Ar name
Only show processes matching
.Ar name .
Can also be of the format
.Ql Li name*
to indicate
.Dq Li begins with ,
.Ql Li *name
to indicate
.Dq Li ends with ,
or
.Ql Li *name*
to indicate
.Dq Li contains .
Can be specified multiple times.
.It Fl K Ar num
Maximum directory depth to display
.Pq Default 64 .
.It Fl l
List available probes on standard output and exit.
.It Fl m
Enable probes matching the specified module names.
.It Fl X Ar profile
Load profile from DWATCH_PROFILES_PATH.
.It Fl n
Enable probes matching the specified probe names.
.It Fl N Ar count
Exit after
.Ar count
matching entries
.Pq Default 0 for disabled .
.It Fl o Ar file
Set output file.
If
.Ql Li - ,
the path
.Ql Li /dev/stdout
is used.
.It Fl O Ar cmd
Execute
.Ar cmd
for each event.
This can be any valid
.Xr sh 1
command.
The environment variables
.Ql Li $TAG
and
.Ql Li $DETAILS
are set for the given
.Ar cmd .
.It Fl p Ar pid
Process id filter.
Only show processes with matching
.Ar pid .
This can be an
.Xr awk 1
regular expression.
.It Fl P
Enable probe matching the specified provider name.
.It Fl q
Quiet.
Hide informational messages and all dtrace(1) errors.
.It Fl Q
List available profiles in DWATCH_PROFILES_PATH and exit.
.It Fl r Ar regex
Filter.
Only show blocks matching
.Xr awk 1
regular expression.
.It Fl R
Show parent,
grandparent,
and ancestor of process.
.It Fl t Ar test
Test clause
.Pq predicate
to limit events
.Pq Default none .
Can be specified multiple times.
.It Fl T Ar time
Timeout.
The format is
.Ql Li #[smhd]
or just
.Ql Li #
for seconds.
.It Fl u Ar user
User filter.
Only show processes matching
.Ar user
name/uid.
This can be an
.Xr awk 1
regular expression to match a numerical UID.
.It Fl v
Verbose.
Show all errors from
.Xr dtrace 1 .
.It Fl V
Report
.Nm
version on standard output and exit.
.It Fl w
Permit destructive actions
.Pq copyout*, stop, panic, etc. .
.It Fl x
Trace.
Print
.Ql Li <probe-id>
when a probe is triggered.
.It Fl y
Always treat stdout as console
.Pq enable colors/columns/etc. .
.It Fl z Ar regex
Only show processes matching
.Xr awk 1
regular expression.
.El
.Sh PROFILES
Profiles customize the data printed during events.
Profiles are loaded from a colon-separated list of directories in
.Ev DWATCH_PROFILES_PATH .
This is an incomplete list of profiles with basic descriptions:
.Bl -tag -width "vop_readdir"
.It chmod
Print mode and path from
.Xr chmod 2 ,
.Xr lchmod 2 ,
.Xr fchmodat 2
.It errno
Print non-zero errno results from system calls
.It io
Print disk I/O details provided by
.Xr dtrace_io 4
.It ip
Print IPv4 and IPv6 details provided by
.Xr dtrace_ip 4
.It kill
Print signal and pid from
.Xr kill 2
.It nanosleep
Print requested time from
.Xr nanosleep 2
.It open
Print path from
.Xr open 2 ,
.Xr openat 2
.It proc
Print process execution details provided by
.Xr dtrace_proc 4
.It proc-signal
Print process signal details provided by
.Xr dtrace_proc 4
.It rw
Print buffer contents from
.Xr read 2 ,
.Xr write 2
.It sched
Print CPU scheduling details provided by
.Xr dtrace_sched 4
.It tcp
Print TCP address/port details provided by
.Xr dtrace_tcp 4
.It tcp-io
Print TCP I/O details provided by
.Xr dtrace_tcp 4
.It udp
Print UDP I/O details provided by
.Xr dtrace_udp 4
.It vop_create
Print filesystem paths being created by
.Xr VOP_CREATE 9
.It vop_lookup
Print filesystem paths being looked-up by
.Xr VOP_LOOKUP 9
.It vop_mkdir
Print directory paths being created by
.Xr VOP_MKDIR 9
.It vop_mknod
Print device node paths being created by
.Xr VOP_MKNOD 9
.It vop_readdir
Print directory paths being read by
.Xr VOP_READDIR 9
.It vop_remove
Print filesystem paths being removed by
.Xr VOP_REMOVE 9
.It vop_rename
Print filesystem paths being renamed by
.Xr VOP_RENAME 9
.It vop_rmdir
Print directory paths being removed by
.Xr VOP_RMDIR 9
.It vop_symlink
Print symlink paths being created by
.Xr VOP_SYMLINK 9
.El
.Sh ENVIRONMENT
These environment variables affect the execution of
.Nm :
.Bl -tag -width "DWATCH_PROFILES_PATH"
.It Ev DWATCH_PROFILES_PATH
If
.Ev DWATCH_PROFILES_PATH
is set,
.Nm
searches for profiles in the colon-separated list of directories in that
variable instead of the default
.Ql Li /usr/libexec/dwatch:/usr/local/libexec/dwatch .
If set to NULL,
profiles are not loaded.
.El
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
Watch processes entering system CPU scheduler.
.Bd -literal -offset indent
dwatch on-cpu
.Ed
.Pp
List available profiles,
one line per profile.
.Bd -literal -offset indent
dwatch -1 -Q
.Ed
.Pp
Do not execute
.Xr dtrace 1
but display script on stdout and exit.
.Bd -literal -offset indent
dwatch -d fsync
.Ed
.Pp
Compile and test but do not execute code generated with given probe.
.Bd -literal -offset indent
dwatch -e test_probe
.Ed
.Pp
Print argument one being passed to each call of zfs_sync().
.Bd -literal -offset indent
dwatch -E 'printf("%i", arg1)' zfs_sync
.Ed
.Pp
Watch all functions named
.Ql Li read .
.Bd -literal -offset indent
dwatch -f read
.Ed
.Pp
Watch all probe traversal.
.Bd -literal -offset indent
dwatch -F :
.Ed
.Pp
Watch syscall probe traversal.
.Bd -literal -offset indent
dwatch -F syscall
.Ed
.Pp
Display only processes belonging to wheel super-group.
.Bd -literal -offset indent
dwatch -g wheel execve
.Ed
.Pp
Display only processes belonging to groups
.Ql Li daemon
or
.Ql Li nobody .
.Bd -literal -offset indent
dwatch -g '1|65534' execve
.Ed
.Pp
Ignore jails,
displaying only base system processes.
.Bd -literal -offset indent
dwatch -j 0 execve
.Ed
.Pp
Display only processes running inside the jail named
.Ql Li myjail .
.Bd -literal -offset indent
dwatch -j myjail execve
.Ed
.Pp
Watch syscall traversal by ruby processes.
.Bd -literal -offset indent
dwatch -k 'ruby*' -F syscall
.Ed
.Pp
Watch syscall traversal by processes containing
.Ql Li daemon
in their name.
.Bd -literal -offset indent
dwatch -k '*daemon*' -F syscall
.Ed
.Pp
Watch signals being passed to
.Xr kill 2 .
.Bd -literal -offset indent
dwatch -X kill
.Ed
.Pp
Watch signals being passed between
.Xr bash 1 Pq Pa ports/shells/bash
and
.Xr vi 1 .
.Bd -literal -offset indent
dwatch -k bash -k vi -X kill
.Ed
.Pp
Display a list of unique functions available.
.Bd -literal -offset indent
dwatch -l -f
.Ed
.Pp
List available probes for functions ending in
.Ql Li read .
.Bd -literal -offset indent
dwatch -l -f '*read'
.Ed
.Pp
List available probes ending in
.Dq Li read .
.Bd -literal -offset indent
dwatch -l -r 'read$'
.Ed
.Pp
Display a list of unique providers.
.Bd -literal -offset indent
dwatch -l -P
.Ed
.Pp
Watch paths being removed by
.Xr VOP_REMOVE 9 .
.Bd -literal -offset indent
dwatch -X vop_remove
.Ed
.Pp
Watch the name
.Ql Li read
instead of the function
.Ql Li read .
The
.Nm
selection algorithm will commonly favor the function named
.Ql Li read
when not given a type
.Pq using So Fl P Sc , So Fl m Sc , So Fl f Sc , or So Fl n Sc
because there are more probes matching the function named
.Ql Li read
than probes matching
.Ql Li read
for any other type.
.Bd -literal -offset indent
dwatch -n read
.Ed
.Pp
Display the first process to call
.Xr kill 2
and then exit.
.Bd -literal -offset indent
dwatch -N 1 kill
.Ed
.Pp
Watch processes forked by pid 1234.
.Bd -literal -offset indent
dwatch -p 1234 execve
.Ed
.Pp
Watch processes forked by either pid 1234 or pid 5678.
.Bd -literal -offset indent
dwatch -p '1234|5678' execve
.Ed
.Pp
Watch the provider
.Ql Li random
instead of the function
.Ql Li random .
The
.Nm
selection algorithm will commonly favor the function named
.Ql Li random
when not given a type
.Pq using So Fl P Sc , So Fl m Sc , So Fl f Sc , or So Fl n Sc
because there are more probes matching the function named
.Ql Li random
than probes matching the provider named
.Ql Li random .
.Bd -literal -offset indent
dwatch -P random
.Ed
.Pp
Display available profiles matching
.Ql Li vop .
.Bd -literal -offset indent
dwatch -Q -r vop
.Ed
.Pp
Watch
.Xr VOP_LOOKUP 9
paths containing
.Ql Li /lib/ .
.Bd -literal -offset indent
dwatch -r /lib/ -X vop_lookup
.Ed
.Pp
Show process tree for each command as it is executed.
.Bd -literal -offset indent
dwatch -R execve
.Ed
.Pp
Watch processes forked by pid 1234 or children thereof.
.Bd -literal -offset indent
dwatch -R -p 1234 execve
.Ed
.Pp
Display processes calling
.Xr write 2
with
.Dq nbytes
less than 10.
.Bd -literal -offset indent
dwatch -t 'arg2<10' -E 'printf("%d",arg2)' write
.Ed
.Pp
Display
.Xr write 2
buffer when
.Dq execname
is not
.Ql Li dtrace
and
.Dq nbytes
is less than 10.
.Bd -literal -offset indent
dwatch -X write -t 'execname != "dtrace" && this->nbytes < 10'
.Ed
.Pp
Watch
.Ql Li statfs
for 5 minutes and exit.
.Bd -literal -offset indent
dwatch -T 5m statfs
.Ed
.Pp
Display only processes belonging to the root super-user.
.Bd -literal -offset indent
dwatch -u root execve
.Ed
.Pp
Display only processes belonging to users
.Ql Li daemon
or
.Ql Li nobody .
.Bd -literal -offset indent
dwatch -u '1|65534' execve
.Ed
.Pp
Print version and exit.
.Bd -literal -offset indent
dwatch -V
.Ed
.Pp
View the first 100 scheduler preemptions.
.Bd -literal -offset indent
dwatch -y -N 100 preempt | less -R
.Ed
.Pp
Display processes matching either
.Dq Li mkdir
or
.Dq Li rmdir .
.Bd -literal -offset indent
dwatch -z '(mk|rm)dir' execve
.Ed
.Pp
Run a command and watch network activity only while that command runs.
.Bd -literal -offset indent
dwatch -X tcp -- -c "nc -zvw10 google.com 22"
.Ed
.Pp
Watch
.Xr open 2
and
.Xr openat 2
calls only while pid 1234 is active.
.Bd -literal -offset indent
dwatch -X open -- -p 1234
.Ed
.Pp
Watch probe traversal for a given command.
Note that
.Dq Li -c true
is passed to
.Xr dtrace 1
since it appears after the
.Nm
probe argument.
.Bd -literal -offset indent
dwatch -F 'pid$target:::entry' -c true
.Ed
.Sh SEE ALSO
.Xr dtrace 1
.Sh HISTORY
.Nm
first appeared in
.Fx 11.2 .
.Sh AUTHORS
.An Devin Teske Aq Mt dteske@FreeBSD.org