在bash中有效地重用printf％s替换中的颜色代码

Question

biwhite=$(tput bold)$(tput setaf 7)
color_off=$(tput sgr0)

printf "%s$USER%s at %s$HOME%s has path %s$PATH%s" "$biwhite" "$color_off" "$biwhite" "$color_off" "$biwhite" "$color_off"

Is there a printf shortcut to avoid having to define every %s when I want to add color to only certain parts of a statement?

Entering "$biwhite" "$color_off" 3 times seems redundant.

Answer 1

It's good practice to avoid putting parameter expansions in the format string of printf , in case they contain percent signs as well. That said, parameter substitution offers a way around some of the repetitiveness.

w="${biwhite}X${color_off}"

printf "%s at %s has path %s" "${w/X/$USER}" "${w/X/$HOME}" "${w/X/$PATH}"

It's not foolproof, but it's fairly unlikely that X will appear in the output of tput . You can pick a longer string instead, at the cost of more typing.

I'm afraid, though, that adding color codes to a string is inherently painful.

Answer 2

I think you could write a bash function:

biwhite=$(tput bold)$(tput setaf 7)
color_off=$(tput sgr0)

whiten() {
  echo "$biwhite$1$color_off"
}

echo "$(whiten "$USER") at $(whiten "$HOME") has path $(whiten "$PATH")"

Also, why use printf if you're not using any of it's formatting capabilities?

Answer 3

Provided below is a function which colorizes every other argument, starting with the second. (Thus, a non-colorized prefix can be provided by passing a non-empty string in this first position, or a colorized one by leaving it empty, as here).

Notably, no subshells are involved in this code's execution except in the tput invocations used for demonstrative purposes. It is thus, while verbose, very low-overhead to execute.

biwhite=$(tput bold)$(tput setaf 7)
color_off=$(tput sgr0)

# colorize every other argument, starting from the 2nd.
colorize_words() {
  local start_color end_color
  : "${start_color:=$biwhite}" "${end_color:=$color_off}"
  while (( $# )); do
    printf '%s' "$1"
    shift || break
    printf '%s%s%s' "$start_color" "$1" "$end_color"
    shift || break
  done
  printf '\n'
}

colorize_words "" "$USER" " at " "$HOME" " has path " "$PATH"

This can be customized by passing start_color and end_color values to an individual invocation; for example:

# this prints every other argument in red
start_color=$(tput setaf 1) colorize_words "hello " "cruel " world