.B _POSIX_MAPPED_FILES
and
.B _POSIX_SYNCHRONIZED_IO
-are defined in \fI<unistd.h>\fP to a value greater than 0.
+are defined in
+.I <unistd.h>
+to a value greater than 0.
(See also
.BR sysconf (3).)
.\" POSIX.1-2001: It shall be defined to -1 or 0 or 200112L.
The
.BR getusershell ()
function returns the next line from the file
-\fI/etc/shells\fP, opening the file if necessary.
+.IR /etc/shells ,
+opening the file if necessary.
The line should contain
the pathname of a valid user shell.
-If \fI/etc/shells\fP does not exist or
+If
+.I /etc/shells
+does not exist or
is unreadable,
.BR getusershell ()
-behaves as if \fI/bin/sh\fP and
-\fI/bin/csh\fP were listed in the file.
+behaves as if
+.I /bin/sh
+and
+.I /bin/csh
+were listed in the file.
.PP
The
.BR setusershell ()
-function rewinds \fI/etc/shells\fP.
+function rewinds
+.IR /etc/shells .
.PP
The
.BR endusershell ()
-function closes \fI/etc/shells\fP.
+function closes
+.IR /etc/shells .
.SH RETURN VALUE
The
.BR getusershell ()
.SH NAME
full \- always full device
.SH CONFIGURATION
-If your system does not have \fI/dev/full\fP created already, it
+If your system does not have
+.I /dev/full
+created already, it
can be created with the following commands:
.nf
chown root:root /dev/full
.fi
.SH DESCRIPTION
-File \fI/dev/full\fP has major device number 1
+File
+.I /dev/full
+has major device number 1
and minor device number 7.
.LP
-Writes to the \fI/dev/full\fP device will fail with an
+Writes to the
+.I /dev/full
+device will fail with an
.B ENOSPC
error.
This can be used to test how a program handles disk-full errors.
-Reads from the \fI/dev/full\fP device will return \\0 characters.
+Reads from the
+.I /dev/full
+device will return \\0 characters.
-Seeks on \fI/dev/full\fP will always succeed.
+Seeks on
+.I /dev/full
+will always succeed.
.SH FILES
/dev/full
.SH SEE ALSO
.SH NAME
ptmx, pts \- pseudoterminal master and slave
.SH DESCRIPTION
-The file \fI/dev/ptmx\fP is a character file with major number 5 and
+The file
+.I /dev/ptmx
+is a character file with major number 5 and
minor number 2, usually of mode 0666 and owner.group of root.root.
It is used to create a pseudoterminal master and slave pair.
.PP
-When a process opens \fI/dev/ptmx\fP, it gets a file
+When a process opens
+.IR /dev/ptmx ,
+it gets a file
descriptor for a pseudoterminal master (PTM),
and a pseudoterminal slave (PTS) device is created in the
.I /dev/pts
directory.
-Each file descriptor obtained by opening \fI/dev/ptmx\fP
+Each file descriptor obtained by opening
+.IR /dev/ptmx
is an independent PTM with its own associated PTS, whose path can
be found by passing the descriptor to
.BR ptsname (3).