watch
—
snoop on another tty line
watch |
[-cinotW ] [-f
snpdev] [tty] |
The watch
utility allows the user to examine all data
coming through a specified tty using the
snp(4)
device. If the
snp(4)
device is not available, watch
will attempt to load
the module (snp
). The watch
utility writes to standard output.
The options are as follows:
-c
- Reconnect on close. If the tty observed by
watch
is closed, automatically reattach to the same tty. If this option is not
specified, watch
will request a new tty if running
in interactive mode or exit if running without a controlling tty.
-f
snpdev
- If this option is specified,
watch
will use
snpdev as the
snp(4)
device. Without this option, watch
will attempt to
find the next available
snp(4)
device.
-i
- Force interactive mode. Interactive mode is a default if
watch
is started from a tty. If output is
redirected to a file, interactive mode can still be requested by
specifying this option.
-n
- Disable the ability to switch the watched tty interactively. This disables
both change requests made with <control-X> as well as automatic
prompting when the current tty is closed or overflows. In all cases where
a prompt would be displayed,
watch
will exit. The
reconnect flags are unaffected by this option. When this flag is used,
<control-X> is passed through to the terminal.
-o
- Reconnect on overflow. The behavior of
watch
if
the observed tty overflows is similar to the behavior if the observed tty
is closed. For more info see
snp(4).
-t
- Print the date and time when observation of a given tty is started.
-W
- Allow write access to observed tty.
- tty
- Tty may be specified as a tty-style device, such as a pseudo tty device, a
virtual console, or a serial line, etc. Names may be preceded by
/dev/.
While running in interactive mode, all user input is discarded except for:
- <control-G>
- Exit
watch
.
- <control-W>
- Clear screen.
- <control-X>
- Change attached tty, unless this feature is disabled, in which case
control-X is passed to the terminal as with other control characters.
The watch
utility first appeared in
FreeBSD 2.1.
No terminal emulation is performed. All user output is reproduced as-is.