gtput, reset - initialize a terminal or query
terminfo database
gtput [-Ttype] capname
[parameters]
gtput [-Ttype] [-x] clear
gtput [-Ttype] init
gtput [-Ttype] reset
gtput [-Ttype] longname
gtput -S <<
gtput -V
The gtput utility uses the terminfo database to make
the values of terminal-dependent capabilities and information available to
the shell (see sh(1)), to initialize or reset the terminal, or return
the long name of the requested terminal type. The result depends upon the
capability's type:
- string
- gtput writes the string to the standard output. No trailing newline
is supplied.
- integer
- gtput writes the decimal value to the standard output, with a
trailing newline.
- boolean
- gtput simply sets the exit code (0 for TRUE if the terminal
has the capability, 1 for FALSE if it does not), and writes nothing
to the standard output.
Before using a value returned on the standard output, the
application should test the exit code (e.g., $?, see sh(1)) to
be sure it is 0. (See the EXIT CODES and DIAGNOSTICS
sections.) For a complete list of capabilities and the capname
associated with each, see terminfo(5).
- -S
- allows more than one capability per invocation of gtput. The
capabilities must be passed to gtput from the standard input
instead of from the command line (see example). Only one capname is
allowed per line. The -S option changes the meaning of the 0
and 1 boolean and string exit codes (see the EXIT CODES
section).
- Because some capabilities may use string parameters rather than
numbers, gtput uses a table and the presence of parameters
in its input to decide whether to use tparm(3X), and how to
interpret the parameters.
- -Ttype
- indicates the type of terminal. Normally this option is
unnecessary, because the default is taken from the environment variable
TERM. If -T is specified, then the shell variables
LINES and COLUMNS will also be ignored.
- -V
- reports the version of ncurses which was used in this program, and
exits.
- -x
- do not attempt to clear the terminal's scrollback buffer using the
extended “E3” capability.
A few commands (init, reset and longname) are
special; they are defined by the gtput program. The others are the
names of capabilities from the terminal database (see
terminfo(5) for a list). Although init and reset
resemble capability names, gtput uses several capabilities to perform
these special functions.
- capname
- indicates the capability from the terminal database.
- If the capability is a string that takes parameters, the arguments
following the capability will be used as parameters for the string.
- Most parameters are numbers. 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
- If the terminal database is present and an entry for the user's terminal
exists (see -Ttype, above), the following will occur:
- (1)
- first, gtput retrieves the current terminal mode settings for your
terminal. It does this by successively testing
- the standard error,
- standard output,
- standard input and
- ultimately “/dev/tty”
- to obtain terminal settings. Having retrieved these settings, gtput
remembers which file descriptor to use when updating settings.
- (2)
- if the window size cannot be obtained from the operating system, but the
terminal description (or environment, e.g., LINES and
COLUMNS variables specify this), update the operating system's
notion of the window size.
- (3)
- the terminal modes will be updated:
- any delays (e.g., newline) specified in the entry will be set in the tty
driver,
- tabs expansion will be turned on or off according to the specification in
the entry, and
- if tabs are not expanded, standard tabs will be set (every 8 spaces).
- (4)
- if present, the terminal's initialization strings will be output as
detailed in the terminfo(5) section on Tabs and
Initialization,
- (5)
- output is flushed.
- If an entry does not contain the information needed for any of these
activities, that activity will silently be skipped.
- reset
- This is similar to init, with two differences:
- (1)
- before any other initialization, the terminal modes will be reset to a
“sane” state:
- set cooked and echo modes,
- turn off cbreak and raw modes,
- turn on newline translation and
- reset any unset special characters to their default values
- (2)
- Instead of putting out initialization strings, the terminal's
reset strings will be output if present (rs1, rs2,
rs3, rf). If the reset strings are not present, but
initialization strings are, the initialization strings will
be output.
- Otherwise, reset acts identically to init.
- longname
- If the terminal database is present and an entry for the user's terminal
exists (see -Ttype above), then the long name of the
terminal will be put out. The long name is the last name in the first line
of the terminal's description in the terminfo database [see
term(5)].
gtput handles the clear, init and
reset commands specially: it allows for the possibility that it is
invoked by a link with those names.
If gtput is invoked by a link named reset, this has
the same effect as gtput reset. The gtset(1) utility also
treats a link named reset specially.
Before ncurses 6.1, the two utilities were different from each
other:
- gtset utility reset the terminal modes and special characters (not
done with gtput).
- On the other hand, gtset's repertoire of terminal capabilities for
resetting the terminal was more limited, i.e., only reset_1string,
reset_2string and reset_file in contrast to the tab-stops
and margins which are set by this utility.
- The reset program is usually an alias for gtset, because of
this difference with resetting terminal modes and special characters.
With the changes made for ncurses 6.1, the reset feature of
the two programs is (mostly) the same. A few differences remain:
- The gtset program waits one second when resetting, in case it
happens to be a hardware terminal.
- The two programs write the terminal initialization strings to different
streams (i.e., the standard error for gtset and the standard output
for gtput).
- Note: although these programs write to different streams,
redirecting their output to a file will capture only part of their
actions. The changes to the terminal modes are not affected by redirecting
the output.
If gtput is invoked by a link named init, this has
the same effect as gtput init. Again, you are less likely to use that
link because another program named init has a more well-established
use.
Besides the special commands (e.g., clear), gtput treats
certain terminfo capabilities specially: lines and cols. gtput
calls setupterm(3X) to obtain the terminal size:
- first, it gets the size from the terminal database (which generally is not
provided for terminal emulators which do not have a fixed window
size)
- then it asks the operating system for the terminal's size (which generally
works, unless connecting via a serial line which 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 finally, the terminal database).
- gtput init
- Initialize the terminal according to the type of terminal in the
environmental variable TERM. This command should be included in
everyone's .profile after the environmental variable TERM has been
exported, as illustrated on the profile(5) manual page.
- gtput -T5620
reset
- Reset an AT&T 5620 terminal, overriding the type of terminal in the
environmental variable TERM.
- gtput cup 0
0
- Send the sequence to move the cursor to row 0, column 0 (the
upper left corner of the screen, usually known as the “home”
cursor position).
- gtput
clear
- Echo the clear-screen sequence for the current terminal.
- gtput
cols
- Print the number of columns for the current terminal.
- gtput -T450
cols
- Print the number of columns for the 450 terminal.
- bold=`gtput
smso` offbold=`gtput rmso`
- Set the shell variables bold, to begin stand-out mode sequence, and
offbold, to end standout mode sequence, for the current terminal.
This might be followed by a prompt: echo "${bold}Please type in
your name: ${offbold}\c"
- gtput hc
- Set exit code to indicate if the current terminal is a hard copy
terminal.
- gtput cup 23
4
- Send the sequence to move the cursor to row 23, column 4.
- gtput
cup
- Send the terminfo string for cursor-movement, with no parameters
substituted.
- gtput
longname
- Print the long name from the terminfo database for the type of
terminal specified in the environmental variable TERM.
gtput -S <<!
> clear
> cup 10 10
> bold
> !
- This example shows gtput processing several capabilities in one
invocation. It clears the screen, moves the cursor to position 10, 10 and
turns on bold (extra bright) mode. The list is terminated by an
exclamation mark (!) on a line by itself.
- /usr/gnu/share/terminfo
- compiled terminal description database
- /usr/gnu/share/tabset/*
- tab settings for some terminals, in a format appropriate to be output to
the terminal (escape sequences that set margins and tabs); for more
information, see the Tabs and Initialization, section of
terminfo(5)
If the -S option is used, gtput checks for errors
from each line, and if any errors are found, will set the exit code to 4
plus the number of lines with errors. If no errors are found, the exit code
is 0. No indication of which line failed can be given so exit code
1 will never appear. Exit codes 2, 3, and 4
retain their usual interpretation. If the -S option is not used, the
exit code depends on the type of capname:
- boolean
- a value of 0 is set for TRUE and 1 for FALSE.
- string
- a value of 0 is set if the capname is defined for this
terminal type (the value of capname is returned on standard
output); a value of 1 is set if capname is not defined for
this terminal type (nothing is written to standard output).
- integer
- a value of 0 is always set, whether or not capname is
defined for this terminal type. To determine if capname is
defined for this terminal type, the user must test the value
written to standard output. A value of -1 means that capname
is not defined for this terminal type.
- other
- reset or init may fail to find their respective files. In
that case, the exit code is set to 4 + errno.
Any other exit code indicates an error; see the DIAGNOSTICS
section.
gtput prints the following error messages and sets the
corresponding exit codes.
exit code |
error message |
0 |
(capname is a numeric variable that is not specified in the
terminfo(5) database for this terminal type, e.g. gtput -T450
lines and gtput -Thp2621 xmc) |
1 |
no error message is printed, see the EXIT CODES section. |
2 |
usage error |
3 |
unknown terminal type or no terminfo database |
4 |
unknown terminfo capability capname |
>4 |
error occurred in -S |
The tput command was begun by Bill Joy in 1980. The initial
version only cleared the screen.
AT&T System V provided a different tput command:
- SVr2 provided a rudimentary tput which checked the parameter
against each predefined capability and returned the corresponding value.
This version of tput did not use tparm(3X) for the
capabilities which are parameterized.
- SVr3 replaced that, a year later, by a more extensive program whose
init and reset subcommands (more than half the program) were
incorporated from the reset feature of BSD tset written by
Eric Allman.
- SVr4 added color initialization using the orig_colors and
orig_pair capabilities in the init subcommand.
Keith Bostic replaced the BSD tput command in 1989 with a
new implementation based on the AT&T System V program tput. Like
the AT&T program, Bostic's version accepted some parameters named for
terminfo capabilities (clear, init, longname and
reset). However (because he had only termcap available), it
accepted termcap names for other capabilities. Also, Bostic's BSD
tput did not modify the terminal I/O modes as the earlier BSD
tset had done.
At the same time, Bostic added a shell script named
“clear”, which used tput to clear the screen.
Both of these appeared in 4.4BSD, becoming the
“modern” BSD implementation of tput.
This implementation of tput began from a different source
than AT&T or BSD: 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. Using the portions dealing with terminal capabilities
almost without change, Raymond made improvements to the way the command-line
parameters were handled.
This implementation of tput differs from AT&T
tput in two important areas:
- •
- gtput capname writes to the standard output. That need not
be a regular terminal. However, the subcommands which manipulate terminal
modes may not use the standard output.
- The AT&T implementation's init and reset commands use
the BSD (4.1c) tset source, which manipulates terminal modes. It
successively tries standard output, standard error, standard input before
falling back to “/dev/tty” and finally just assumes a 1200Bd
terminal. When updating terminal modes, it ignores errors.
- Until changes made after ncurses 6.0, gtput did not modify terminal
modes. gtput now uses a similar scheme, using functions shared with
gtset (and ultimately based on the 4.4BSD tset). If it is
not able to open a terminal, e.g., when running in cron(1),
gtput will return an error.
- •
- AT&T tput guesses the type of its capname operands by
seeing if all of the characters are numeric, or not.
- Most implementations which provide support for capname operands use
the tparm function to expand parameters in it. That function
expects a mixture of numeric and string parameters, requiring gtput
to know which type to use.
- This implementation uses a table to determine the parameter types for the
standard capname operands, and an internal library function to
analyze nonstandard capname operands.
- Besides providing more reliable operation than AT&T'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. That had been modified to interpret
multiple commands on a line. Portable applications should not rely upon
this feature; ncurses provides it to support applications written
specifically for OpenBSD.
This implementation (unlike others) can accept both termcap
and terminfo names for the capname feature, if termcap
support is compiled in. However, the predefined termcap and
terminfo names have two ambiguities in this case (and the
terminfo name is assumed):
- The termcap name dl corresponds to the terminfo name
dl1 (delete one line).
The terminfo name dl corresponds to the termcap name
DL (delete a given number of lines).
- The termcap name ed corresponds to the terminfo name
rmdc (end delete mode).
The terminfo name ed corresponds to the termcap name
cd (clear to end of screen).
The longname and -S options, and the
parameter-substitution features used in the cup example, were not
supported in BSD curses before 4.3reno (1989) or in AT&T/USL curses
before SVr4 (1988).
IEEE Std 1003.1/The Open Group Base Specifications Issue 7
(POSIX.1-2008) documents only the operands for clear, init and
reset. There are a few interesting observations to make regarding
that:
- In this implementation, clear is part of the capname
support. The others (init and longname) do not correspond to
terminal capabilities.
- Other implementations of tput on SVr4-based systems such as
Solaris, IRIX64 and HPUX as well as others such as AIX and Tru64 provide
support for capname operands.
- A few platforms such as FreeBSD recognize termcap names rather than
terminfo capability names in their respective tput commands. Since
2010, NetBSD's tput uses terminfo names. Before that, it (like
FreeBSD) recognized termcap names.
- Beginning in 2021, FreeBSD uses the ncurses tput, configured for
both terminfo (tested first) and termcap (as a fallback).
Because (apparently) all of the certified Unix systems
support the full set of capability names, the reasoning for documenting only
a few may not be apparent.
- X/Open Curses Issue 7 documents tput differently, with
capname 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 capabilities
database.
- While it is certainly possible to write a tput program without
using curses, none of the systems which have a curses implementation
provide a tput utility which does not provide the capname
feature.
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 (i.e., Unix features documented in SVID 3):
- It assigns exit code 4 to “invalid operand”, which may be
the same as unknown capability. For instance, the source code for
Solaris' xcurses uses the term “invalid” in this case.
- It assigns exit code 255 to a numeric variable that is not specified in
the terminfo database. That likely is a documentation error, confusing the
-1 written to the standard output for an absent or cancelled
numeric value versus an (unsigned) exit code.
The various Unix systems (AIX, HPUX, Solaris) use the same
exit-codes as ncurses.
NetBSD curses documents different exit codes which do not
correspond to either ncurses or X/Open.