0

I want to change the text colour in a shell. I can use tput to get the correct escape codes. For example,

echo "$(tput setaf 5)My text$(tput sgr0)"

outputs My text in a pink-ish tone.

This works fine on Linux, macOS, FreeBSD, NetBSD, and Solaris. On OpenBSD 7.2, however, I get the following error:

tput: not enough arguments (3) for capability `setaf'

According to the OpenBSD docs of tput, the attribute should be defined in terminfo or termcap. I don't see setaf defined in the docs for termcap, so I assume tput interprets setaf as defined in the docs for terminfo. According to those docs:

To change the current foreground or background color on a Tektronix-type terminal, use setaf (set ANSI foreground) and setab (set ANSI background) or setf (set foreground) and setb (set background). These take one parameter, the color number.

This conflicts what I've been told by the error message. On the other hand, I can use tput setaf 5 0 0 and, regardless of the last two parameters, the foreground colour is changed to pink-ish.

Why does tput require three parameters on OpenBSD, and what do those extra two parameters mean?

Improve this question
1
  • 1
    This is probably a duplicate (I recall it being answered before). It's a known bug in the OpenBSD copy of tput. Perhaps someday OpenBSD will upgrade, and fix its problems. Commented Feb 17, 2023 at 20:06

2 Answers 2

Reset to default
1

Standard expectations from as far back as I can remember using tput on a variety of UNIX-type systems (two decades? probably more) are:

  • The tput setaf requires a single number following that indicates the ANSI colour number to use. Anything else is likely to be a bug.
  • tput sgr0 requires no parameter.
  • You can chain them (tput setaf 5 sgr0) but this particular construct would make no sense as you would be issuing a colour change that was immediately reset.

In your situation I would reiterate that tput setaf requiring more than one number is likely to be a bug.

On my Debian-based system (bullseye) I have found that tput setaf 5 0 0 is accepted, with the unexpected trailing values ignored (no error), so you might be able to satisfy the OpenBSD bug without breaking other systems. (The same applies for other tput commands: additional trailing arguments are accepted but ignored.) However, if this isn't always the case, code like this might provide a suitable but necessary workaround:

# Work around OpenBSD bug https://gitlab.com/jschx/ufetch/-/merge_requests/61
tputbug=; tput setaf 0 >/dev/null 2>&1 || tputbug='0 0'

tput setaf 2 $tputbug

As an aside, if you were going to use lots of colour codes my recommendation would be to capture them in variables so that the command execution was performed once per colour rather than once per line:

magenta=$(tput setaf 5 $tputbug)
normal=$(tput sgr0)

echo "${magenta}My text${normal}"

Further note for other readers: variables don't normally require curly braces ($magenta is quite acceptable) but in this case they are used to separate the variable name from the immediately following text. Otherwise you would have an unset variable called $magentaMy.

Improve this answer
4
  • Unfortunately, the tput setaf sgr0 is just a typo from when I wrote the question (I fixed the question now), I can confirm that the bug is indeed specifically due to tput setaf 1, because running only that command on the command line gives me the indicated error. It makes sense that it's an error, but OpenBSD is probably the Unix I used the least, so I started by assuming I made a mistake. And thank you for the suggestion of re-using tput output, though in my case the output is used only once ^^ Commented Feb 17, 2023 at 22:12
  • 1
    Thank you for the update! Simply using all three arguments indeed works on both OpenBSD and Debian Bookworm, but on Debian Testing it gives me the error tput: unknown terminfo capability '0'. And unfortunately, I agree with that error, because tput allows you to specify multiple commands in sequence: tput setaf 5 0 0 is like tput setaf 5 followed by tput setaf 0 0, and that second command is not valid :-( Commented Feb 18, 2023 at 15:06
  • 1
    @FWDekker there you go. Another proposal, tested as best I can given I don't have Bookworm Commented Feb 18, 2023 at 15:27
  • Oh nice, that's creative. I had written my own answer to this question, and while I saw one other solution checking the error output of tput, I think yours is much shorter and more elegant :-) Commented Feb 18, 2023 at 15:30
0

As Thomas Dickey pointed out in his comment to this question, this is a known bug where tput incorrectly calculates the required number of arguments, which has already been reported to OpenBSD; this is in addition to several other problems with OpenBSD's tput which basically result from OpenBSD's tput being outdated.

It looks like this bug has been encountered many times before by others ([1] [2] [3] [4] [5]). Obviously, the correct solution would be to fix this bug in OpenBSD, but I don't have the know-how to do that.

I've seen three possible workarounds:

  • Stuart Henderson recommended in the OpenBSD mailing list to use tput setaf 5 0 0 as a workaround, where the last two arguments are bogus. This works fine on OpenBSD, but results in errors on other systems, meaning that you'd have to detect OpenBSD and dynamically change how you invoke tput.
  • Set TERM=xterm if you detect OpenBSD is running. The drawback is that OpenBSD users have only 8 colours.
  • Check if tput setaf 5 returns an error, and change how you invoke tput depending on that.

In my case, I'll not spend any effort trying to work around or fix the issue. If a user of mine encounters this issue, they can choose to disable the colour feature of my program, revive the bug report on OpenBSD, or try to fix the bug in OpenBSD themselves.

Improve this answer

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.