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   tput    ( 1 )

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Портативность (Portability)

This implementation of tput differs from AT&T tput in two important areas:

• @TPUT@ 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, @TPUT@ did not modify terminal modes. @TPUT@ now uses a similar scheme, using functions shared with @TSET@ (and ultimately based on the 4.4BSD tset). If it is not able to open a terminal, e.g., when running in cron, @TPUT@ 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 @TPUT@ 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.

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.