window(1)window(1)NAMEwindow - Implements a window environment
SYNOPSISwindow [-dft] [-c command] [-e] [escape_character]
The window command implements a window environment on ASCII terminals.
OPTIONS
Executes the string command as a long command (see Long Commands)
before doing anything else. Ignores and creates the two default win‐
dows instead. Sets the Escape character to escape_character. The
escape_character can be a single character, or in the form <Ctrl-x>,
where x is any character. Does not perform any start-up action (Fast
option). Turns on terse mode (see the terse command later in this ref‐
erence page).
DESCRIPTION
A window is a rectangular portion of the physical terminal screen asso‐
ciated with a set of processes. Its size and position can be changed
by the user at any time. Processes communicate with their window in
the same way they normally interact with a terminal--through their
standard input, output, and diagnostic file descriptors. The window
program handles the details of redirecting input and output to and from
the windows. At any one time, only one window can receive input from
the keyboard, but all windows can simultaneously send output to the
display.
Windows can overlap and are framed as necessary. Each window is named
by one of the digits 1 to 9. This 1-character identifier, as well as a
user-definable label string, are displayed with the window on the top
edge of its frame. A window can be designated to be in the foreground,
in which case it will always be on top of all normal, nonforeground
windows, and can be covered only by other foreground windows. A window
need not be completely within the edges of the terminal screen. Thus,
a large window (possibly larger than the screen) can be positioned to
show only a portion of its full size.
Each window has a cursor and a set of control functions. Most program‐
mable terminal operations, such as line and character deletion and
insertion, are supported. Display modes, such as underlining and
reverse video, are available if they are supported by the terminal. In
addition, like terminals with multiple pages of memory, each window has
a text buffer that can have more lines than the window itself.
When window starts up, the commands (see Long Commands) contained in
the file in the user's home directory are executed. If the file does
not exist, two equal-sized windows spanning the terminal screen are
created by default.
Process Environment
With each newly created window, a shell program is spawned with its
process environment tailored to that window. Its standard input, out‐
put, and diagnostic file descriptors are bound to one end of either a
pseudoterminal (pty or a UNIX domain socket, socketpair. If a pseu‐
doterminal is used, then its special characters and modes (see the stty
command) are copied from the physical terminal. A termcap entry tai‐
lored to this window is created and passed as environment (environ)
variable TERMCAP. The termcap entry contains the window's size and
characteristics as well as information from the physical terminal, such
as the existence of underline, reverse video, and other display modes,
and the codes produced by the terminal's function keys, if any. In
addition, the window size attributes of the pseudoterminal are set to
reflect the size of this window, and updated whenever it is changed by
the user. In particular, the editor vi uses this information to redraw
its display.
Operation
During normal execution, window can be in one of two states: conversa‐
tion mode and command mode. In conversation mode, the terminal's real
cursor is placed at the cursor position of a particular window (called
the current window), and input from the keyboard is sent to the process
in that window. The current window is always on top of all other win‐
dows, except those in foreground. In addition, it is set apart by
highlighting its identifier and label in reverse video.
Typing window's Escape character (normally ^P) in conversation mode
switches it into command mode. In command mode, the top line of the
terminal screen becomes the command prompt window, and window inter‐
prets input from the keyboard as commands to manipulate windows.
There are two types of commands: short commands are usually one or two
keystrokes; long commands are strings that are typed in the command
window (see the : command under Short Commands) or read from a file
(see the built-in function source under Built-In Functions).
Short Commands
The # variable represents one of the digits 1 to 9 corresponding to the
windows 1 to 9. The sequence ^X means <Ctrl-x>, where x is any charac‐
ter. In particular, ^^ is <Ctrl-^>. escape is the <Esc> key, or ^[.
Selects window # as the current window and returns to conversation
mode. Selects window #, but stays in command mode. Selects the previ‐
ous window and returns to conversation mode. This is useful for tog‐
gling between two windows. Returns to conversation mode. Returns to
conversation mode and writes ^P to the current window. Thus, typing
two ^Ps in conversation mode sends one to the current window. If the
window Escape character is changed to some other character, that char‐
acter takes the place of ^P here. Lists a short summary of commands.
Redraws the screen. Exits window after requesting confirmation. Sus‐
pends window. Creates a new window. You are prompted for the posi‐
tions of the upper-left and lower-right corners of the window. The cur‐
sor is placed on the screen and the keys <h>, <j>, <k>, and <l> move
the cursor left, down, up, and right, respectively. The keys <H>, <J>,
<K>, and <L> move the cursor to the respective limits of the screen.
Typing a number before the movement keys repeats the movement that num‐
ber of times. Pressing <Return> enters the cursor position as the
upper-left corner of the window. The lower-right corner is entered in
the same manner. During this process, the placement of the new window
is indicated by a rectangular box drawn on the screen, corresponding to
where the new window will be framed. Pressing escape (see preceding
description) at any point cancels this command.
This new window becomes the current window, and is given the
first available ID. The default buffer size is used (see the
built-in function nline under Built-In Functions). Only fully
visible windows can be created this way. Closes window #. The
process in the window is sent the Hangup signal (see the kill
command). The csh command should handle this signal correctly
and cause no problems. Moves window # to another location. A
box in the shape of the window is drawn on the screen to indi‐
cate the new position of the window, and the same keys as those
for the w command are used to position the box. The window can
be moved partially off the screen. Moves window # to its previ‐
ous position. Changes the size of window #. You are prompted
to enter the new lower-right corner of the window. A box is
drawn to indicate the new window size. The same keys used in w
and m are used to enter the position. Changes window # to its
previous size. Scrolls the current window up by one line.
Scrolls the current window down by one line. Scrolls the cur‐
rent window up by half the window size. Scrolls the current
window down by half the window size. Scrolls the current window
up by the full window size. Scrolls the current window down by
the full window size. Moves the cursor of the current window
left by one column. Moves the cursor of the current window down
by one line. Moves the cursor of the current window up by one
line. Moves the cursor of the current window right by one col‐
umn. Stops output in the current window. Starts output in the
current window. Enters a line to be executed as long commands.
Normal line editing characters (erase character, erase word,
erase line) are supported.
Long Commands
Long commands are a sequence of statements parsed much like a program‐
ming language, with a syntax similar to that of C. Numeric and string
expressions and variables are supported, as well as conditional state‐
ments.
There are two data types: string and number. A string is a sequence of
letters or digits beginning with a letter. The _ (underscore) and
(dot) characters are considered letters. Alternately, nonalphanumeric
characters can be included in strings by escaping them with a \ (back‐
slash). In addition, the \ sequences of C are supported, both inside
and outside quotes (that is, \n is a newline, and \r a carriage-
return). The following are also legal strings: abcde01234, $^*,
ab$#cd, ab\$\#cd, /usr/bin/window.
A number is an integer value in one of three forms: a decimal number,
an octal number preceded by 0 (zero), or a hexadecimal number preceded
by 0x or 0X. The natural machine integer size is used (the signed
integer type of the C compiler). As in C, a nonzero number represents
a Boolean TRUE.
The # (number sign) begins a comment that terminates at the end of the
line.
A statement is either a conditional or an expression. Expression
statements are terminated with a newline or with the ; (semicolon)
character. To continue an expression on the next line, terminate the
first line with a \ (backslash).
Conditional Statements
The window command has a single control structure: the fully bracketed
if statement in the following form: if <expression> then <state‐
ment> . . . elsif <expression> then <statement> . . .
else <statement> . . . endif
The else and elsif parts are optional, and the latter can be repeated
any number of times. expression must be numeric.
Expressions
Expressions in window are similar to those in the C language, with most
C operators supported on numeric operands. In addition, some are over‐
loaded to operate on strings.
When an expression is used as a statement, its value is discarded after
evaluation. Therefore, only expressions with side effects (assignments
and function calls) are useful as statements.
Single-valued (no arrays) variables are supported for both numeric and
string values. Some variables are predefined. They are listed as fol‐
lows:
The operators in order of increasing precedence are as follows: Assigns
the variable <expression1>, which must be string valued, to the result
of <expression2>. Returns the value of <expression2>. Returns the
value of <expression2> if <expression1> evaluates TRUE (nonzero numeric
value); returns the value of <expression3> otherwise. Either <expres‐
sion2> and <expression3> is evaluated, but not both. <expression1> must
be numeric. Performs a logical OR. Numeric values only. Short circuit
evaluation is supported (that is, if <expression1> evaluates TRUE, then
<expression2> is not evaluated). Performs a logical AND with short
circuit evaluation. Numeric values only. Performs a bitwise OR.
Numeric values only. Performs a bitwise exclusive OR. Numeric values
only. Performs a bitwise AND. Numeric values only. <expression1> !=
<expression2>
Performs a comparison (equal and not equal, respectively). The
Boolean result (either 1 or 0) is returned. The operands can be
numeric or string valued. One string operand forces the other
to be converted to a string if necessary. <expression1> >
<expression2>, <expression1> <= <expression2>, <expression1> >=
<expression2>
Performs a less than, greater than, less than or equal to,
greater than or equal to operation. Both numeric and string
values, with automatic conversion as stated previously.
<expression1> >> <expression2>
Bit shifts <expression1> left (or right) by <expression2> bits
if both operands are numbers. If <expression1> is a string,
then its first (or last) <expression2> characters are returned
(if <expression2> is also a string, then its length is used in
place of its value). <expression1> - <expression2>
Performs addition and subtraction on numbers. For +, if one
argument is a string, then the other is converted to a string,
and the result is the concatenation of the two strings.
<expression1> / <expression2>, <expression1> % <expression2>
Performs multiplication, division, modulo. Numbers only.
$<expression>, $?<expression>
Performs unary minus, bitwise complement, and logical complement
on numbers only (the first three expressions, respectively). The
operator, $, takes <expression> and returns the value of the
variable of that name. If <expression> is numeric with value n
and it appears within an alias macro (described later), then it
refers to the nth argument of the alias invocation. $? tests
for the existence of the variable <expression>, and returns 1 if
it exists or 0 otherwise. Performs a function call. <expres‐
sion> must be a string that is the unique prefix of the name of
a built-in window function or the full name of a user-defined
alias macro. In the case of a built-in function, <argu‐
ment_list> can be in one of two forms: <expression1>, <expres‐
sion2>, ...
argument1 = <expression1>, argument2 = <expression2>, ...
The two forms can in fact be intermixed, but the result is
unpredictable. Most arguments can be omitted; default values
will be supplied for them. Arguments can be unique prefixes of
the argument names. The commas separating arguments are used
only to prevent ambiguity, and can usually be omitted.
Only the first argument form is valid for user-defined aliases.
Aliases are defined using the alias built-in function (described
later). Arguments are accessed through a variant of the vari‐
able mechanism (see $ operator previously described).
Most functions return a value, but some are used for side
effects only and so must be used as statements. When a function
or an alias is used as a statement, the parentheses surrounding
the argument list can be omitted. Aliases return no value.
Built-In Functions
The arguments are listed by name in their natural order. Optional
arguments are in [ ] (brackets). Arguments that have no names are in <
> (angle brackets). Lists all currently defined alias macros, if no
argument is given. Otherwise, <string> is defined as an alias, with
expansion <string_list>. The previous definition of <string>, if any,
is returned. Default for <string_list> is no change. Closes the win‐
dows specified in <window_list>. If <window_list> is the word all, all
windows are closed. No value is returned. Sets the window cursor to
modes. modes is the bitwise OR of the mode bits defined as the vari‐
ables m_ul (underline), m_rev (reverse video), m_blk (blinking), and
m_grp (graphics, terminal dependent). Return value is the previous
modes. Default is no change. For example, cursor($m_rev|$m_blk) sets
the window cursors to blinking reverse video. Writes the list of
strings, <string_list>, to window, separated by spaces and terminated
with a newline. The strings are only displayed in the window; the pro‐
cesses in the window are not involved (see the built-in function write,
under Built-In Functions). No value is returned. Default is the cur‐
rent window. Sets the Escape character to escape_character. Returns
the old Escape character as a 1-character string. Default is no
change. escape_character can be a string of a single character, or in
the form ^X, meaning <Ctrl-x>. Moves window in or out of foreground.
flag can be on, off, yes, no, true, or false, with obvious meanings, or
it can be a numeric expression, in which case a nonzero value is TRUE.
Returns the old foreground flag as a number. Default for window is the
current window; default for flag is no change. Sets the label of win‐
dow to label. Returns the old label as a string. Default for window
is the current window; default for label is no change. To turn off a
label, set it to an empty string (" "). Lists the identifiers and
labels of all windows. No value is returned. Sets the default buffer
size to nline. Initially, it is 48 lines. Returns the old default
buffer size. Default is no change. Using a very large buffer can slow
the program down considerably. Makes window the current window. The
previous current window is returned. Default is no change. Sets the
default window shell program to <string_list>. Returns the first
string in the old shell setting. Default is no change. Initially, the
default shell is taken from the SHELL environment variable. Reads and
executes the long commands in file. Returns -1 if the file cannot be
read, 0 otherwise. Sets terse mode to flag. In terse mode, the com‐
mand window stays hidden even in command mode, and errors are reported
by sounding the terminal's bell. The flag can take on the same values
as in foreground. Returns the old terse flag. Default is no change.
Undefines alias. Returns -1 if alias does not exist, 0 otherwise.
Undefines variable. Returns -1 if variable does not exist, 0 other‐
wise. Lists all variables. No value is returned. Opens a window with
upper-left corner at row (row), column (column) and of size nrow, ncol‐
umn. If nline is specified, then that many lines are allocated for the
text buffer. Otherwise, the default buffer size is used. Default val‐
ues for row, column, nrow, and ncolumn are, respectively, the upper,
leftmost, lower, or rightmost extremes of the screen. The frame
(frame), pty, and mapnl (mapnl) are flag values interpreted in the same
way as the argument to foreground (previously described); they mean,
respectively, put a frame around this window (default TRUE), allocate
pseudoterminal for this window rather than socketpair (default TRUE),
and map newline characters in this window to carriage-return and line‐
feed (default TRUE if socketpair is used, FALSE otherwise). sh is a
list of strings that will be used as the shell program to place in the
window (default is the program specified by shell). The created win‐
dow's identifier is returned as a number. Sends the list of strings,
<string_list>, to window, separated by spaces but not terminated with a
newline. The strings are actually given to the window as input. No
value is returned. Default is the current window.
Predefined Variables
These variables are for information only. Redefining them does not
affect the internal operation of window. The baud rate as a number
between 50 and 38,400. The display modes (reverse video, underline,
blinking, graphics) supported by the physical terminal. The value of
modes is the bitwise OR of some of the 1-bit values, m_blk, m_grp,
m_rev, and m_ul. These values are useful in setting the window cursor
modes (see cursormodes under Built-In Functions). The blinking mode
bit. The graphics mode bit (not very useful). The reverse video mode
bit. The underline mode bit. The number of columns on the physical
screen. The number of rows on the physical screen. The terminal type.
The standard name, found in the second name field of the terminal's
TERMCAP entry, is used.
FILES
Start-up file. Pseudoterminal devices.
SEE ALSO
Commands: stty(1)
The environ variable.
window(1)