Add a description of the special kernel thread "ioflush" to the "special

processes" section, per PR 10912. While we're here, clean up nroff nits,
like spaces at the ends of lines.

lib/libc/sys/intro.2

@@ -1,4 +1,4 @@
-.\"	$NetBSD: intro.2,v 1.22 2000/03/14 19:14:29 kleink Exp $
+.\"	$NetBSD: intro.2,v 1.23 2001/03/13 03:24:13 fair Exp $
 .\"
 .\" Copyright (c) 1980, 1983, 1986, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -95,7 +95,8 @@ An asynchronous signal (such as
 or
 .Dv SIGQUIT )
 was caught by the process during the execution of an interruptible
-function. If the signal handler performs a normal return, the
+function.
+If the signal handler performs a normal return, the
 interrupted function call will seem to have returned the error condition.
 .It Er 5 EIO Em "Input/output error" .
 Some physical input or output error occurred.
@@ -181,8 +182,8 @@ not a directory, when a directory was expected.
 .It Er 21 EISDIR Em "Is a directory" .
 An attempt was made to open a directory with write mode specified.
 .It Er 22 EINVAL Em "Invalid argument" .
-Some invalid argument was supplied. (For example,
+Some invalid argument was supplied.
-specifying an undefined signal to a
+(For example, specifying an undefined signal to a
 .Xr signal 3
 or
 .Xr kill 2
@@ -211,11 +212,12 @@ while the pure procedure file was being executed an
 .Xr open 2
 call requested write access.
 .It Er 27 EFBIG Em "File too large" .
-The size of a file exceeded the maximum.  (The system-wide maximum file size is
+The size of a file exceeded the maximum.
+(The system-wide maximum file size is
 .if t 2\u\s-263\s+2\d
 .if n 2**63
-bytes.  Each file system may impose a lower limit for files contained within
+bytes.
-it.)
+Each file system may impose a lower limit for files contained within it).
 .It Er 28 ENOSPC Em "Device out of space" .
 A
 .Xr write 2
@@ -235,9 +237,9 @@ An attempt was made to modify a file or directory
 was made
 on a file system that was read-only at the time.
 .It Er 31 EMLINK Em "Too many links" .
-The number of hard links to a single file has exceeded the maximum.  (The
+The number of hard links to a single file has exceeded the maximum.
-system-wide maximum number of hard links is 32767.  Each file system may
+(The system-wide maximum number of hard links is 32767.
-impose a lower limit for files contained within it.)
+Each file system may impose a lower limit for files contained within it).
 .It Er 32 EPIPE Em "Broken pipe" .
 A write on a pipe, socket or
 .Tn FIFO
@@ -270,7 +272,8 @@ A message sent on a socket was larger than the internal message buffer
 or some other network limit.
 .It Er 41 EPROTOTYPE Em "Protocol wrong type for socket" .
 A protocol was specified that does not support the semantics of the
-socket type requested. For example, you cannot use the
+socket type requested.
+For example, you cannot use the
 .Tn ARPA
 Internet
 .Tn UDP
@@ -319,9 +322,9 @@ The host you were connected to crashed and rebooted.
 .It Er 53 ECONNABORTED Em "Software caused connection abort" .
 A connection abort was caused internal to your host machine.
 .It Er 54 ECONNRESET Em "Connection reset by peer" .
-A connection was forcibly closed by a peer.  This normally
+A connection was forcibly closed by a peer.
-results from a loss of the connection on the remote socket
+This normally results from a loss of the connection on the remote
-due to a timeout or a reboot.
+socket due to a timeout or a reboot.
 .It Er 55 ENOBUFS Em "\&No buffer space available" .
 An operation on a socket or pipe was not performed because
 the system lacked sufficient buffer space or because a queue was full.
@@ -350,11 +353,12 @@ A
 or
 .Xr send 2
 request failed because the connected party did not
-properly respond after a period of time.  (The timeout
+properly respond after a period of time.
-period is dependent on the communication protocol.)
+(The timeout period is dependent on the communication protocol).
 .It Er 61 ECONNREFUSED Em "Connection refused" .
 No connection could be made because the target machine actively
-refused it.  This usually results from trying to connect
+refused it.
+This usually results from trying to connect
 to a service that is inactive on the foreign host.
 .It Er 62 ELOOP Em "Too many levels of symbolic links" .
 A path name lookup involved more than 8 symbolic links.
@@ -394,8 +398,7 @@ filesystem)
 which is now unavailable as referenced by the file descriptor.
 This may indicate the file was deleted on the
 .Tn NFS
-server or some 
+server or some other catastrophic event occurred.
-other catastrophic event occurred.
 .It Er 72 EBADRPC Em "RPC struct is bad" .
 Exchange of
 .Tn RPC
@@ -447,7 +450,8 @@ A wide character/multibyte character encoding error occured.
 .Bl -tag -width Ds
 .It  Process ID .
 Each active process in the system is uniquely identified by a non-negative
-integer called a process ID.  The range of this ID is from 0 to 30000.
+integer called a process ID.
+The range of this ID is from 0 to 30000.
 .It  Parent process ID
 A new process is created by a currently active process; (see
 .Xr fork 2 ) .
@@ -457,9 +461,9 @@ the parent process ID of each child is set to the ID of a system process,
 .Xr init 8 .
 .It  Process Group
 Each active process is a member of a process group that is identified by
-a non-negative integer called the process group ID.  This is the process
+a non-negative integer called the process group ID.
-ID of the group leader.  This grouping permits the signaling of related
+This is the process ID of the group leader.
-processes (see
+This grouping permits the signaling of related processes (see
 .Xr termios 4 )
 and the job control mechanisms of
 .Xr csh 1 .
@@ -513,9 +517,9 @@ termed the real user ID.
 .Pp
 Each user is also a member of one or more groups.
 One of these groups is distinguished from others and
-used in implementing accounting facilities.  The positive
+used in implementing accounting facilities.
-integer corresponding to this distinguished group is termed 
+The positive integer corresponding to this distinguished group is
-the real group ID.
+termed the real group ID.
 .Pp
 All processes have a real user ID and real group ID.
 These are initialized from the equivalent attributes
@@ -530,17 +534,18 @@ group IDs, and it is unspecified whether the effective group ID is
 a member of the list.)
 .Pp
 The effective user ID and effective group ID are initially the
-process's real user ID and real group ID respectively.  Either
+process's real user ID and real group ID respectively.
-may be modified through execution of a set-user-ID or set-group-ID
+Either may be modified through execution of a set-user-ID or
-file (possibly by one its ancestors) (see
+set-group-ID file (possibly by one its ancestors) (see
 .Xr execve 2 ) .
 By convention, the effective group ID (the first member of the group access
 list) is duplicated, so that the execution of a set-group-ID program
 does not result in the loss of the original (real) group ID.
 .Pp
 The group access list is a set of group IDs
-used only in determining resource accessibility.  Access checks
+used only in determining resource accessibility.
-are performed as described below in ``File Access Permissions''.
+Access checks are performed as described below in
+.Qq File Access Permissions .
 .It  "Saved Set User ID and Saved Set Group ID"
 When a process executes a new file, the effective user ID is set
 to the owner of the file if the file is set-user-ID, and the effective
@@ -559,13 +564,21 @@ A process is recognized as a
 .Em super-user
 process and is granted special privileges if its effective user ID is 0.
 .It  Special Processes
-The processes with process IDs of 0, 1, 2 and 3 are special.
+The processes with process IDs of 0, 1, 2, 3, and 4 are special.
-Process 0 is the scheduler.  Process 1 is the initialization process
+Process 0 is the scheduler.
+Process 1 is the initialization process
 .Xr init 8 ,
-and is the ancestor of every other process in the system.
+and is the ancestor (parent) of every other process in the system.
 It is used to control the process structure.
-Process 2 is the paging daemon.  Process 3 is the reaper, which handles
+Process 2 is the paging daemon.
-deallocating resources for exiting processes.
+Process 3 is the
+.Sy reaper ,
+which handles deallocating resources for exiting processes.
+Process 4 is
+.Sy ioflush ,
+which replaces the old
+.Sy update
+program that periodically flushes the disk buffer cache.
 .It  Descriptor
 An integer assigned by the system when a file is referenced
 by
@@ -592,8 +605,8 @@ excluding 0 (NUL) and the
 .Tn ASCII
 code for
 .Ql \&/
-(slash).  (The parity bit,
+(slash).
-bit 7, must be 0.)
+(The parity bit, bit 7, must be 0).
 .Pp
 Note that it is generally unwise to use
 .Ql \&* ,
@@ -620,13 +633,13 @@ If a path name begins with a slash, the path search begins at the
 .Em root
 directory.
 Otherwise, the search begins from the current working directory.
-A slash by itself names the root directory.  An empty
+A slash by itself names the root directory.
-pathname refers to the current directory.
+An empty pathname refers to the current directory.
 .It  Directory
 A directory is a special type of file that contains entries
 that are references to other files.
-Directory entries are called links.  By convention, a directory
+Directory entries are called links.
-contains at least two links,
+By convention, a directory contains at least two links,
 .Ql \&.
 and
 .Ql \&.. ,
@@ -634,40 +647,42 @@ referred to as
 .Em dot
 and
 .Em dot-dot
-respectively.  Dot refers to the directory itself and
+respectively.
-dot-dot refers to its parent directory.
+Dot refers to the directory itself and dot-dot refers to its parent directory.
 .It "Root Directory and Current Working Directory"
 Each process has associated with it a concept of a root directory
 and a current working directory for the purpose of resolving path
-name searches.  A process's root directory need not be the root
+name searches.
+A process's root directory need not be the root
 directory of the root file system.
 .It  File Access Permissions
 Every file in the file system has a set of access permissions.
 These permissions are used in determining whether a process
 may perform a requested operation on the file (such as opening
-a file for writing).  Access permissions are established at the
+a file for writing).
-time a file is created.  They may be changed at some later time
+Access permissions are established at the time a file is created.
-through the 
+They may be changed at some later time through the
 .Xr chmod 2
 call.
 .Pp
 File access is broken down according to whether a file may be: read,
-written, or executed.  Directory files use the execute
+written, or executed.
-permission to control if the directory may be searched. 
+Directory files use the execute permission to control if the
+directory may be searched.
 .Pp
 File access permissions are interpreted by the system as
 they apply to three different classes of users: the owner
 of the file, those users in the file's group, anyone else.
 Every file has an independent set of access permissions for
-each of these classes.  When an access check is made, the system
+each of these classes.
-decides if permission should be granted by checking the access
+When an access check is made, the system decides if permission should be
-information applicable to the caller.
+granted by checking the access information applicable to the caller.
 .Pp
 Read, write, and execute/search permissions on
 a file are granted to a process if:
 .Pp
-The process's effective user ID is that of the super-user. (Note:
+The process's effective user ID is that of the super-user.
-even the super-user cannot execute a non-executable file.)
+(Note: even the super-user cannot execute a non-executable file).
 .Pp
 The process's effective user ID matches the user ID of the owner
 of the file and the owner permissions allow the access.
@@ -701,9 +716,10 @@ for more information about the types available and
 their properties.
 .Pp
 Each instance of the system supports some number of sets of
-communications protocols.  Each protocol set supports addresses
+communications protocols.
-of a certain format.  An Address Family is the set of addresses
+Each protocol set supports addresses of a certain format.
-for a specific group of protocols.  Each socket has an address
+An Address Family is the set of addresses for a specific group of protocols.
+Each socket has an address
 chosen from the address family in which the socket was created.
 .El
 .Sh SEE ALSO