pg.1

<B>Digital的Unix操作系统VAX 4.2源码</B>

.TH pg 1
.SH Name
pg \- file perusal filter for soft-copy terminals
.SH Syntax
.B pg
.BI [\- number ]
.B [\-p
.IB string ]
.B [\-cefs]
.BI [+ linenumber ]
.BI [+/ pattern /]
.BR [ files ...]
.SH Description
.NXR "pg command"
The
.PN pg
command is a filter that allows the examination
of
.I files
one screenful
at a time on a soft-copy terminal.
When the file name is
designated by a minus (\-) and/or NULL argument,
the
.PN pg
command reads from the standard input.
Each screenful is followed by a prompt.
If the user types a carriage return, another page is displayed.
.PP
This command is different from previous paginators
because it allows you to back up
and review material that has already passed.
.PP
In order to determine terminal attributes,
.PN pg
scans the
.MS terminfo 5
data base for the terminal type specified by the
environment variable
TERM.
If
TERM
is not defined,
the terminal is assumed to be a
dumb terminal.
The
.PN pg
command takes responses that
can be divided
into three categories: those causing further perusal, those that
search, and those that modify the perusal environment.
.PP
Commands causing further perusal normally take a preceding
.IR address,
which is an optionally signed number indicating the point from which
further text should be displayed.
This
.I address
is interpreted in either pages or lines depending
on the command.
A signed
.I address
specifies a point relative to the current page
or line, and an unsigned
.I address
specifies an address relative
to the beginning of the file.
Each command has a default address that is used if none is provided.
.PP
The perusal commands and their defaults are as follows:
.TP 20
.RI (+1)< newline "> or <" blank >
Causes one page to be displayed.
The address is specified in pages.
.TP
.RB "(+1) " l
Causes
.PN pg
to simulate scrolling the screen, forward or backward,
the number of lines specified when used with a relative address.
With an absolute address
this command prints a screenful
beginning at the specified line.
.TP
.RB "(+1) " d " or " ^D
Simulates scrolling half a screen forward or backward.
.PP
The following perusal commands take no
.IR address:
.TP 20
.BR . " or " ^L
Causes the current page of text
to be redisplayed.
.TP
.B $
Displays the last window full in the file.
Use with caution when the input is a pipe.
.PP
The following commands are available for searching for text patterns
in the text.
The regular expressions described in
.MS ed 1
are available.
They must always be terminated by a
.RI < newline >,
even if the
.I \-n
option is specified.
.TP 20
.IB i / pattern /
Searches forward for the
.IR i th
(default
.IR i =1)
occurrence
of
.IR pattern.
Searching begins immediately after the current page and continues to the
end of the current file, without wrap-around.
.PP
.IB i ^ pattern ^
.PD 0
.TP
.IB i ? pattern ?
Searches backwards for the
.IR i th
(default
.IR i =1)
occurrence of
.IR pattern.
Searching begins immediately before the current page
and continues to the beginning of the current file, without
wrap-around.
The circumflex (^) notation is useful for Adds 100 terminals
which do not
handle the question mark (?) properly.
.PD
.PP
After searching,
.PN pg
normally displays the line found at the top of the screen.
This can be modified by appending m or b
to the search
command to leave the line found in the middle or at the bottom of
the window from now on.
The suffix t
can be used to restore the original situation.
.PP
The user of
.PN pg
can modify the environment of perusal with the
following commands:
.TP 20
.IB i n
Begins perusing the
.IR i th
next file in the command line.
The
.I i
is an unsigned number.  Default value is 1.
.TP
.IB i 
Begins perusing the
.IR i th
previous file in the command line.
.I i
is an unsigned number.  Default is 1.
.TP
.IB i w
Displays another window of text.
If
.I i
is present, sets the window size to
.IR i.
.TP
.BI "s " filename
Saves the input in the named file.
Only the current file being perused is saved.
The white space between the
.B s
and
.I filename
is optional.
This command must always be terminated by a
.RI < newline >,
even if the
.I \-n
option is specified.
.TP
.B h
Helps by displaying an abbreviated summary of available commands.
.TP
.BR q " or " Q "
Quits
.PN pg .
.TP
\fB!\fIcommand\fR
The
.I command
is passed to the shell, whose name is
taken from the
SHELL
environment variable.
If this is not available, the default shell is used.
This command must always be terminated by a
.RI < newline >,
even if the
.B \-n
option is specified.
.PP
At any time when output is being sent to the terminal, the user can hit
the quit key (normally control-\\) or the interrupt (break) key.
This causes
.PN pg
to stop sending output and to display the prompt.
The user may then enter one of the above commands in the normal manner.
Unfortunately, some output is lost when this is done, because
any characters waiting in the terminal's output queue are flushed
when the quit signal occurs.
.PP
If the standard output is not a terminal, then
.PN pg
acts just like
.MS cat 1 ,
except that a header is printed before each file (if there is
more than one).
.SH Options
The command line options are:
.TP 15
.I \-number
Specifies the size (in lines)
of the window that
.PN pg
is to use instead of the default.
(On a terminal containing 24 lines, the default window size is 23).
.TP
.BI \-p " string"
Causes
.PN pg
to use 
.PN string
as the prompt.
If the prompt string contains a %d, the first occurrence
of %d in the prompt is replaced
by the current page number when the prompt is issued.
The default prompt string is designated by a colon
.RB (:) .
.TP
.B \-c
Homes the cursor and clears the screen before displaying each page.
This option is ignored if
.B clear_screen
is not defined for this terminal type in the
.MS terminfo 5
data base.
.TP
.B \-e
Causes
.PN pg
.I not
to pause at the end of each file.
.TP
.B \-f
Inhibits
.PN pg
from splitting lines.
Normally,
.PN pg
splits lines longer than the screen width,
but some sequences of characters
in the text being displayed
(for example, escape sequences for underlining)
generate undesirable results.
The
.I \-f
option prevents the splitting of these sequences.
.TP
.B \-s
Causes 
.PN pg
to print all messages and prompts in standout
mode (usually inverse video).
.TP
.BI + linenumber
Starts up at
.IR linenumber.
.TP
.BI +/ pattern /
Starts up at the first line containing
the regular expression pattern.
.SH Examples
The following example shows how the
.PN pg
command is used reading system news:
.EX
news | pg \-p "(Page %d):"
.EE
.SH Notes
While waiting for terminal input,
.PN pg
responds to
.BR \s-1BREAK\s+1 ,
.BR \s-1DEL\s+1 
and the circumflex (^)
by terminating execution.
Between prompts, however, these signals interrupt
.PN pg
command's
current task and place the user in prompt mode.
These should be used with caution when input is being read from
a pipe, since an interrupt is likely to terminate the other
commands in the pipeline.
.SH Restrictions
Terminal tabs must be set every eight positions.
.PP
Using
.PN pg
as a filter with another command changes the terminal I/O
options.  For example,
.MS crypt 1 
terminal settings may not be restored correctly.
.SH Files
.TP 22
.PN /usr/lib/terminfo/*
Terminal information data base
.TP
.PN /tmp/pg*
Temporary file when input is from a pipe
.SH See Also
crypt(1), ed(1), grep(1), terminfo(5)