gtput - initialize a terminal, exercise its capabilities,
or query terminfo database
gtput [-T terminal-type] {cap-code
[parameter ...]} ...
gtput [-T terminal-type] [-x]
clear
gtput [-T terminal-type] init
gtput [-T terminal-type] reset
gtput [-T terminal-type] longname
gtput -S
gtput -V
gtput uses the terminfo library and database to make
terminal-specific capabilities and information available to the shell, to
initialize or reset the terminal, or to report a description of the current
(or specified) terminal type. Terminal capabilities are accessed by
cap-code.
terminfo(5) discusses terminal capabilities at length and
presents a complete list of cap-codes.
When retrieving capability values, the result depends upon the
capability's type.
- Boolean
- gtput sets its exit status to 0 if the terminal possesses
cap-code, and 1 if it does not.
- numeric
- gtput writes cap-code's decimal value to the standard output
stream if defined (-1 if it is not) followed by a newline.
- string
- gtput writes cap-code's value to the standard output stream
if defined, without a trailing newline.
Before using a value returned on the standard output, the
application should test gtput's exit status to be sure it is 0; see
section “EXIT STATUS” below.
Generally, an operand is a cap-code, a capability code from
the terminal database, or a parameter thereto. Three others are specially
recognized by gtput: init, reset, and longname.
Although these resemble capability codes, they in fact receive special
handling; we term them “pseudo-capabilities”.
- cap-code
- indicates a capability from the terminal database.
- If cap-code is of string type and takes parameters, gtput
interprets arguments following cap-code as the parameters, up to
the (fixed) quantity the capability requires.
- Most parameters are numeric. Only a few terminal capabilities require
string parameters; gtput uses a table to decide which to pass as
strings. Normally gtput uses tparm(3X) to perform the
substitution. If no parameters are given for the capability, gtput
writes the string without performing the substitution.
- init
- initializes the terminal. If the terminal database is present and an entry
for the user's terminal type exists, the following occur.
- (1)
- gtput retrieves the terminal's mode settings. It successively tests
the file descriptors corresponding to
- the standard error stream,
- the standard output stream,
- the standard input stream, and
- /dev/tty
- to obtain terminal settings. Having retrieved them, gtput remembers
which descriptor to use for further updates.
- (2)
- If the terminal dimensions cannot be obtained from the operating system,
but the environment or terminal type database entry describes them,
gtput updates the operating system's notion of them.
- (3)
- gtput updates the terminal modes.
- Any delays specified in the entry (for example, when a newline is sent)
are set in the terminal driver.
- Tab expansion is turned on or off per the specification in the entry,
and
- if tabs are not expanded, standard tabs (every 8 spaces) are set.
- (4)
- If initialization capabilities, detailed in subsection “Tabs and
Initialization” of terminfo(5), are present, gtput
writes them to the standard output stream.
- (5)
- gtput flushes the standard output stream.
- If an entry lacks the information needed for an activity above, that
activity is silently skipped.
- reset
- re-initializes the terminal. A reset differs from initialization in two
ways.
- (1)
- gtput sets the the terminal modes to a “sane”
state,
- enabling cooked and echo modes,
- disabling cbreak and raw modes,
- enabling newline translation, and
- setting any unset special characters to their default values.
- (2)
- If any reset capabilities are defined for the terminal type, gtput
writes them to the output stream. Otherwise, gtput uses any defined
initialization capabilities. Reset capabilities are detailed in subsection
“Tabs and Initialization” of terminfo(5).
- longname
- A terminfo entry begins with one or more names by which an
application can refer to the entry, before the list of terminal
capabilities. The names are separated by “|” characters.
X/Open Curses terms the last name the “long name”, and
indicates that it may include blanks.
- gtic warns if the last name does not include blanks, to accommodate
old terminfo entries that treated the long name as an optional
feature. The long name is often referred to as the description field.
- If the terminal database is present and an entry for the user's terminal
type exists, gtput reports its description to the standard output
stream, without a trailing newline. See terminfo(5).
Note: Redirecting the output of “gtput
init” or “gtput reset” to a file will
capture only part of their actions. Changes to the terminal modes are not
affected by file descriptor redirection, since the terminal modes are
altered via ioctl(2).
If gtput is invoked via link with any of the names
clear, init, or reset, it operates as if run with the
corresponding (pseudo-)capability operand. For example, executing a link
named reset that points to gtput has the same effect as
“gtput reset”.
This feature was introduced by ncurses 5.2 in 2000. It is
rarely used:
- clear
- is a separate program, which is both smaller and more frequently
executed.
- init
- has the same name as another program in widespread use.
- reset
- is provided by the gtset(1) utility (also via a link named
reset).
Besides the pseudo-capabilities (such as init),
gtput treats the lines and cols cap-codes
specially: it may call setupterm(3X) to obtain the terminal size.
- First, gtput attempts to obtain these capabilities from the
terminal database. This generally fails for terminal emulators, which lack
a fixed window size and thus omit the capabilities.
- It then asks the operating system for the terminal's size, which generally
works, unless the connection is via a serial line that does not support
“NAWS”: negotiations about window size.
- Finally, it inspects the environment variables LINES and
COLUMNS, which may override the terminal size.
If the -T option is given, gtput ignores the
environment variables by calling use_tioctl(TRUE), relying upon the
operating system (or, ultimately, the terminal database).
- -S
- retrieves more than one capability per invocation of gtput. The
capabilities must be passed to gtput from the standard input stream
instead of from the command line (see section “EXAMPLES”
below). Only one cap-code is allowed per line. The -S option
changes the meanings of the 0 and 1 exit statuses (see
section “EXIT STATUS” below).
- Some capabilities use string parameters rather than numeric ones.
gtput employs a built-in table and the presence of parameters in
its input to decide how to interpret them, and whether to use
tparm(3X).
- -T type
- indicates the terminal's type. Normally this option is unnecessary,
because a default is taken from the TERM environment variable. If
specified, the environment variables LINES and COLUMNS are
also ignored.
- -V
- reports the version of ncurses associated with gtput, and
exits with a successful status.
- -x
- prevents “gtput clear” from attempting to clear the
scrollback buffer.
Normally, one should interpret gtput's exit statuses as
follows.
| Status |
Meaning When -S Not Specified |
| 0 |
Boolean or string capability present |
| 1 |
Boolean or numeric capability absent |
| 2 |
usage error or no terminal type specified |
| 3 |
unrecognized terminal type |
| 4 |
unrecognized capability code |
| >4 |
system error (4 + errno) |
When the -S option is used, some statuses change
meanings.
| Status |
Meaning When -S Specified |
| 0 |
all operands interpreted |
| 1 |
unused |
| 4 |
some operands not interpreted |
gtput reads one environment variable.
- TERM
- denotes the terminal type. Each terminal type is distinct, though many are
similar. The -T option overrides its value.
- /usr/gnu/share/tabset
- tab stop initialization database
- /usr/gnu/share/terminfo
- compiled terminal description database
Over time ncurses gtput has differed from that of
System V in two important respects, one now mostly historical.
- •
- “gtput cap-code” writes to the standard
output, which need not be a terminal device. However, the operands that
manipulate terminal modes might not use the standard output.
- System V tput's init and reset operands use
logic from 4.1cBSD tset, manipulating terminal modes. It checks the
same file descriptors (and /dev/tty) for association with a
terminal device as ncurses now does, and if none are, finally
assumes a 1200 baud terminal. When updating terminal modes, it ignores
errors.
- Until ncurses 6.1 (see section “HISTORY” below),
gtput did not modify terminal modes. It now employs a scheme
similar to System V, using functions shared with gtset (and
ultimately based on 4.4BSD tset). If it is not able to open a
terminal (for instance, when run by cron(1)), gtput exits
with an error status.
- •
- System V tput assumes that the type of a cap-code
operand is numeric if all the characters of its value are decimal numbers;
if they are not, it treats cap-code as a string capability.
- Most implementations that provide support for cap-code operands use
the tparm(3X) function to expand its parameters. That function
expects a mixture of numeric and string parameters, requiring gtput
to know which type to use.
- ncurses gtput uses a table to determine the parameter types
for the standard cap-code operands, and an internal function to
analyze nonstandard cap-code operands.
- While more reliable than System V's utility, a portability problem
is introduced by this analysis. An OpenBSD developer adapted the internal
library function from ncurses to port NetBSD's termcap-based
tput to terminfo, and modified it to interpret multiple
cap-codes (and parameters) on the command line. Portable
applications should not rely upon this feature; ncurses offers it
to support applications written specifically for OpenBSD.
This implementation, unlike others, accepts both termcap
and terminfo cap-codes if termcap support is compiled
in. In that case, however, the predefined termcap and terminfo
codes have two ambiguities; ncurses assumes the terminfo
code.
- The cap-code dl means delete_line to termcap
but parm_delete_line to terminfo. termcap uses the
code DL for parm_delete_line. terminfo uses the code
dl1 for delete_line.
- The cap-code ed means exit_delete_mode to
termcap but clr_eos to terminfo. termcap uses
the code cd for clr_eos. terminfo uses the code
rmdc for exit_delete_mode.
The longname operand, -S option, and the
parameter-substitution features used in the cup example below, were
not supported in AT&T/USL curses before SVr4 (1989). Later,
4.3BSD-Reno (1990) added support for longname, and in 1994, NetBSD
added support for the parameter-substitution features.
IEEE Std 1003.1/The Open Group Base Specifications Issue 7
(POSIX.1-2008) documents only the clear, init, and
reset operands. A few observations of interest arise from that
selection.
- ncurses supports clear as it does any other standard
cap-code. The others (init and longname) do not
correspond to terminal capabilities.
- The tput on SVr4-based systems such as Solaris, IRIX64, and HP-UX,
as well as others such as AIX and Tru64, also support standard
cap-code operands.
- A few platforms such as FreeBSD recognize termcap codes rather than
terminfo capability codes in their respective tput commands.
Since 2010, NetBSD's tput uses terminfo codes. Before that,
it (like FreeBSD) recognized termcap codes.
- Beginning in 2021, FreeBSD uses ncurses tput, configured for
both terminfo (tested first) and termcap (as a
fallback).
Because (apparently) all certified Unix systems support the
full set of capability codes, the reason for documenting only a few may not
be apparent.
- X/Open Curses Issue 7 documents tput differently, with
cap-code and the other features used in this implementation.
- That is, there are two standards for tput: POSIX (a subset) and
X/Open Curses (the full implementation). POSIX documents a subset to avoid
the complication of including X/Open Curses and the terminal capability
database.
- While it is certainly possible to write a tput program without
using curses, no system with a curses implementation
provides a tput utility that does not also support standard
cap-codes.
X/Open Curses Issue 7 (2009) is the first version to document
utilities. However that part of X/Open Curses does not follow existing
practice (that is, System V curses behavior).
- It assigns exit status 4 to “invalid operand”, which may
have the same meaning as “unknown capability”. For instance,
the source code for Solaris xcurses uses the term
“invalid” in this case.
- It assigns exit status 255 to a numeric variable that is not specified in
the terminfo database. That likely is a documentation error,
mistaking the “-1” written to the standard output to
indicate an absent or cancelled numeric capability for an (unsigned) exit
status.
The various System V implementations (AIX, HP-UX, Solaris)
use the same exit statuses as ncurses.
NetBSD curses documents exit statuses that correspond to
neither ncurses nor X/Open Curses.
Bill Joy wrote a tput command during development of 4BSD in
October 1980. This initial version only cleared the screen, and did not ship
with official distributions.
System V developed a different tput command.
- SVr2 (1984) provided a rudimentary tput that checked the parameter
against each predefined capability and returned the corresponding value.
This version of tput did not use tparm(3X) for parameterized
capabilities.
- SVr3 (1987) replaced that with a more extensive program whose support for
init and reset operands (more than half the program)
incorporated the reset feature of BSD tset written by Eric
Allman.
- SVr4 (1989) added color initialization by using the orig_colors
(oc) and orig_pair (op) capabilities in its
init logic.
Keith Bostic refactored BSD tput for shipment in
4.3BSD-Tahoe (1988), then replaced it the next year with a new
implementation based on System V tput. Bostic's version
similarly accepted some parameters named for terminfo
(pseudo-)capabilities: clear, init, longname, and
reset. However, because he had only termcap available, it
accepted termcap codes for other capabilities. Also, Bostic's BSD
tput did not modify the terminal modes as the earlier BSD tset
had done.
At the same time, Bostic added a shell script named
“clear” that used tput to clear the screen. Both of
these appeared in 4.4BSD, becoming the “modern” BSD
implementation of tput.
The origin of ncurses gtput lies outside both
System V and BSD, in Ross Ridge's mytinfo package, published
on comp.sources.unix in December 1992. Ridge's program made more
sophisticated use of the terminal capabilities than the BSD program. Eric
Raymond used that tput program (and other parts of mytinfo) in
ncurses in June 1995. Incorporating the portions dealing with
terminal capabilities almost without change, Raymond made improvements to
the way command-line parameters were handled.
Before ncurses 6.1 (2018), its gtset and
gtput utilities differed.
- gtset was more effective, resetting the terminal modes and special
characters.
- On the other hand, gtset's repertoire of terminal capabilities for
resetting the terminal was more limited; it had only equivalents of
reset_1string (rs1), reset_2string (rs2), and
reset_file (rf), and not the tab stop and margin update
features of gtput.
The reset program is traditionally an alias for
gtset due to its ability to reset terminal modes and special
characters.
As of ncurses 6.1, the “reset” features of
the two programs are (mostly) the same. Two minor differences remain.
- The gtset program waits one second when resetting, in case the
terminal happens to be a hardware device.
- The two programs write the terminal initialization strings to different
streams; that is, standard error for gtset and standard output for
gtput.
- gtput init
- Initialize the terminal according to the type of terminal in the
TERM environment variable. If the system does not reliably
initialize the terminal upon login, this command can be included in
$HOME/.profile after exporting the TERM environment
variable.
- gtput -T5620
reset
- Reset an AT&T 5620 terminal, overriding the terminal type in the
TERM environment variable.
- gtput
cnorm
- Set cursor to normal visibility.
- gtput
home
- Move the cursor to row 0, column 0: the upper left corner of the screen,
usually known as the “home” cursor position.
- gtput
clear
- Clear the screen: write the clear_screen capability's value to the
standard output stream.
- gtput
cols
- Report the number of columns used by the current terminal type.
- gtput -Tadm3a
cols
- Report the number of columns used by an ADM-3A terminal.
- strong=`gtput smso`
normal=`gtput rmso`
- Set shell variables to capability values: strong and normal,
to begin and end, respectively, stand-out mode for the terminal. One might
use these to present a prompt.
printf "${strong}Username:${normal} "
- gtput hc
- Indicate via exit status whether the terminal is a hard copy device.
- gtput cup 23
4
- Move the cursor to row 23, column 4.
- gtput
cup
- Report the value of the cursor_address (cup) capability
(used for cursor movement), with no parameters substituted.
- gtput
longname
- Report the terminfo database's description of the terminal type
specified in the TERM environment variable.
- gtput
-S
- Process multiple capabilities. The -S option can be profitably used
with a shell “here document”.
-
$ gtput -S <<!
> clear
> cup 10 10
> bold
> !
- The foregoing clears the screen, moves the cursor to position (10, 10) and
turns on bold (extra bright) mode.
- gtput clear cup 10
10 bold
- Perform the same actions as the foregoing “gtput -S”
example.