From 533f4c5076d3f3d0ea7cb5e3c1d1df37ce05a18d Mon Sep 17 00:00:00 2001
From: Paul Traina <pst@FreeBSD.org>
Date: Thu, 23 Feb 1995 01:25:48 +0000
Subject: [PATCH] Clean up man page

---
 share/man/man4/snp.4 | 113 +++++++++++++++++++++++++++----------------
 1 file changed, 72 insertions(+), 41 deletions(-)

diff --git a/share/man/man4/snp.4 b/share/man/man4/snp.4
index 47b97d8ae896..f2930701d247 100644
--- a/share/man/man4/snp.4
+++ b/share/man/man4/snp.4
@@ -1,49 +1,80 @@
-.Dd Februar 17, 1995
-.Dt SNP(4)
-.Os
+.\"
+.\" 	@(#)snp.4	1.1 (FreeBSD) 2/17/95
+.\"
+.Dd February 17, 1995
+.Dt SNP 4
+.Os FreeBSD
 .Sh NAME
-
- snp  - tty snoop interface.
-
+.Nm snp
+.Nd tty snoop interface
 .Sh SYNOPSIS
-#include <sys/snoop.h>
-
+.Fd #include <sys/ioctl.h>
+.Fd #include <sys/snoop.h>
+.Ft int
+.Fn ioctl fd SNPSTTY &snptty
+.Ft int
+.Fn ioctl fd SNPGTTY &snptty
+.Ft int
+.Fn ioctl fd FIONREAD 0
 .Sh DESCRIPTION
- /dev/snp? are snoop devices which allow user to attach to any tty
-and watch activities on it. Device can be used by root only.
- To connect device to tty use special iocontrol SNPSTTY.Argument to
-it is a structure 'snptty'. 
-              struct snptty {
-                     int st_type;
-                     int st_unit;
-              }
+/dev/snp? are snoop devices which allow user to attach to any tty
+and watch activities on it.
 
-st_type - type of tty to attach. Currently supported are :
-       ST_PTY - pseudo-tty devices.
-       ST_VTY - virtual ttys (syscons).
-       ST_SIO - serial ttys.
+To associate a given
+.Nm snp
+device with a tty to be observed,  open the
+.Nm snp
+device and then use the SNPSTTY ioctl.
+The argument passed to the IOCTL is the address of a structure of
+the following type:
+.Bd -literal -ffset indent
+struct snptty {
+	int	st_type;		/* type of the tty to attach */
+	int	st_unit;		/* number of the tty unit */
+}
 
-st_unit - number of tty unit.
-By specifying ever st_type or st_unit -1 user can detach snp 
-device from tty.
-
- SNPGTTY  - iocontrol returns current tty attached.
- FIONREAD - iocontrol returns ever positive value equal to number of
-            characters in read buffer. Also special values defined:
-             SNP_OFLOW    - device overflow occured,device automatically
-                            detached.
-             SNP_TTYCLOSE - tty still has not been attached.       
-             SNP_DETACH   - snp device has been detached by user or
-                            tty device has been closed and detached
-                            automatically.
-  
+#define	ST_PTY		0		/* regular pty */
+#define	ST_VTY		1		/* syscons vty */
+#define	ST_SIO		2		/* serial lines */
+.Ed
+.Pp
+By setting st_type or st_unit to -1, the user may detach the snp device
+for a tty.
+.Pp
+The SNPGTTY ioctl returns information about the current tty attached to
+the open
+.Nm snp
+device.
+.Pp
+The FIONREAD ioctl returns a positive value equal to the number of characters
+in a read buffer.
+Special values defined are:
+.Bl -tag -width SNP_TTYCLOSE
+.It Dv SNP_OFLOW
+device overflow occured, device detatched.
+.It Dv SNP_TTYCLOSE
+tty not attached.
+.It Dv SNP_DETACH
+.Nm snp
+device has been detatched by user or tty device has been closed
+and detatched.
 .Sh SEE ALSO
-
-watch(8), pty(4), sio(4)
+.Xr watch 8 ,
+.Xr pty 4 ,
+.Xr sio 4
+.Sh RESTRICTIONS
+Only the superuser may access the
+.Nm snp
+devices.
 .Sh BUGS
-
-While in line mode,user input can't be seen.
-Has no ability to write to attached tty device.
-
+While in line mode, user input can't be seen.
+.Nm
+snp
+is a read-only device, there is no ability to write to attached tty device.
+.Sh AUTHOR
+Ugen J.S. Antsilevich <ugen@NetVision.net.il>
 .Sh HISTORY
-FreeBSD 2.1 by Ugen J.S.Antsilevich <ugen@NetVision.net.il>
+The
+.Nm
+snp
+device first appeared in FreeBSD 2.1.