4
\$\begingroup\$

My goal with the below piece of POSIX shell code was to address the more platforms the better with shell tput colors. With this code, I now start all of my scripts, and so it's time to review it for some things I overlooked, did not think of too well, and such. Note: I start my scripts with set -u, which is why I set all empty in unspecified cases. Thanks.

#!/bin/sh

set -u

if tput setaf > /dev/null 2>&1; then
    # Linux-like
    tput_number_of_colors=$(tput colors 2> /dev/null)
    tput_bold=$(tput bold 2> /dev/null)
    tput_reset=$(tput sgr0 2> /dev/null)
    tput_cmd_set_fg_color='tput setaf'
elif tput AF > /dev/null 2>&1; then
    # BSD-like
    tput_number_of_colors=$(tput Co 2> /dev/null)
    tput_bold=$(tput md 2> /dev/null)
    tput_reset=$(tput me 2> /dev/null)
    tput_cmd_set_fg_color='tput AF'
else
    # Console-like
    tput_number_of_colors=2
    tput_cmd_set_fg_color=
    tput_bold=
    tput_reset=
fi

tput_test ()
{
    [ -n "$tput_number_of_colors" ] && [ -n "$tput_bold" ] && [ -n "$tput_reset" ] &&
    { [ "$tput_number_of_colors" -ge 8 ] && printf '%s' "$tput_bold" && $tput_cmd_set_fg_color 1; } > /dev/null 2>&1
}

if tput_test; then
    color_red=$tput_bold$($tput_cmd_set_fg_color 1)
    color_green=$tput_bold$($tput_cmd_set_fg_color 2)
    color_yellow=$tput_bold$($tput_cmd_set_fg_color 3)
    color_blue=$tput_bold$($tput_cmd_set_fg_color 4)
    color_magenta=$tput_bold$($tput_cmd_set_fg_color 5)
    color_cyan=$tput_bold$($tput_cmd_set_fg_color 6)
    color_white=$tput_bold$($tput_cmd_set_fg_color 7)
else
    color_red=; color_green=; color_yellow=; color_blue=; color_magenta=; color_cyan=; color_white=
fi
\$\endgroup\$

2 Answers 2

Reset to default
3
\$\begingroup\$

Self-review

Since no one replied thus far, I decided to re-think and re-write the code myself this morning.

terminfo (*nix) vs termcap (*bsd)

I never really thought about how important to make note of this actually is. For searching info online, one needs to know these keywords. So, I added them as comments.

Structure into functions

I believe this code should be structured into suitable functions where available.

Find a way for an exit code from those functions

It's needed to simply chain (&&) the commands like tput_bold=$(tput bold 2> /dev/null) && tput_reset=$(tput sgr0 2> /dev/null) in order for the imagined functions to return a reliable exit code.

The most basic test missing

command -v tput was missing in my code, which is remedied now.

No unset variables

Since I use set -u in my scripts, it's necessary to set variables empty in case of failure. This feature has been enhanced.

Modified code

#!/bin/sh

set -u

tput_setup_nix ()
{
    # terminfo
    tput_cmd_set_fg_color='tput setaf'
    tput_number_of_colors=$(tput colors 2> /dev/null) &&
    tput_bold=$(tput bold 2> /dev/null) &&
    tput_reset=$(tput sgr0 2> /dev/null)
}

tput_setup_bsd ()
{
    # termcap
    tput_cmd_set_fg_color='tput AF'
    tput_number_of_colors=$(tput Co 2> /dev/null) &&
    tput_bold=$(tput md 2> /dev/null) &&
    tput_reset=$(tput me 2> /dev/null)
}

tput_setup_none ()
{
    # no unset variables
    tput_cmd_set_fg_color=
    tput_number_of_colors=
    tput_bold=
    tput_reset=
}

if command -v tput > /dev/null 2>&1; then

    if tput setaf > /dev/null 2>&1; then

        if ! tput_setup_nix; then tput_setup_none; fi

    elif tput AF > /dev/null 2>&1; then

        if ! tput_setup_bsd; then tput_setup_none; fi

    else
        tput_setup_none
    fi

else
    tput_setup_none
fi

tput_capability_test ()
{
    [ -n "$tput_cmd_set_fg_color" ] && [ -n "$tput_number_of_colors" ] && [ -n "$tput_bold" ] && [ -n "$tput_reset" ] &&
    [ "$tput_number_of_colors" -ge 8 ] && { $tput_cmd_set_fg_color 1 && printf '%s' "$tput_bold$tput_reset"; } > /dev/null 2>&1

}

if tput_capability_test; then
    color_red=$tput_bold$($tput_cmd_set_fg_color 1)
    color_green=$tput_bold$($tput_cmd_set_fg_color 2)
    color_yellow=$tput_bold$($tput_cmd_set_fg_color 3)
    color_blue=$tput_bold$($tput_cmd_set_fg_color 4)
    color_magenta=$tput_bold$($tput_cmd_set_fg_color 5)
    color_cyan=$tput_bold$($tput_cmd_set_fg_color 6)
    color_white=$tput_bold$($tput_cmd_set_fg_color 7)
else
    color_red=
    color_green=
    color_yellow=
    color_blue=
    color_magenta=
    color_cyan=
    color_white=
fi
\$\endgroup\$
2
  • \$\begingroup\$ I don't see how the command -v tput adds anything, except complexity. If there's no available tput command, then we get error return from trying to execute it. Also, you can simplify if ! tput_setup_nix; then tput_setup_none; fi to simple tput_setup_nix || tput_setup_none. \$\endgroup\$ Commented Oct 11, 2022 at 15:45
  • \$\begingroup\$ @TobySpeight Correct, command -v did not add anything. \$\endgroup\$ Commented Oct 12, 2022 at 22:34
1
\$\begingroup\$

2022 review

I found myself time for another self-review now, two years later.

Main features

  • Simplified code, better readability.

  • Removed unnecessary tests.

  • Shortened code, rather unimportant.

Modified code

# Linux uses terminfo; BSD uses termcap; the null command (:) ignores everything after
tput_init_linux () { set_fg_color='tput setaf'; reset_color=$(tput sgr0 2>/dev/null); }
tput_init_bsd   () { set_fg_color='tput AF';    reset_color=$(tput me   2>/dev/null); }
tput_init_none  () { set_fg_color=':';          reset_color=;                         }

# This routine prepares `tput` on Linux and BSD and no color console
if tput setaf >/dev/null 2>&1; then tput_init_linux || tput_init_none;
elif tput AF  >/dev/null 2>&1; then tput_init_bsd   || tput_init_none;
else tput_init_none; fi

no_color () { printf '%s' "$reset_color"; }
colorize ()
{
    case "$1" in
        (red)     $set_fg_color 1 ;;
        (green)   $set_fg_color 2 ;;
        (yellow)  $set_fg_color 3 ;;
        (blue)    $set_fg_color 4 ;;
        (magenta) $set_fg_color 5 ;;
        (cyan)    $set_fg_color 6 ;;
        (white)   $set_fg_color 7 ;;
        (*) printf '%s\n' "This color ('$1') is not supported. Quitting!" >&2; exit 1 ;;
    esac
}

color_red=$(colorize red)
color_green=$(colorize green)
color_yellow=$(colorize yellow)
color_blue=$(colorize blue)
color_magenta=$(colorize magenta)
color_cyan=$(colorize cyan)
color_white=$(colorize white)
color_none=$(no_color)
\$\endgroup\$
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