Skip printing on line matching regex pattern

Question

How can I skip printing on the line that matches pattern. For remaining lines display with the corresponding printf until a new line matches another pattern.

Want I want is the Wht:, Grn:, and Blu: codes to indicate the colour of subsequent text. So they're not to be output but instead used for changing the colour setting.

Here's what I have so far, which handles colouring but but doesn't do what I want:

theone ()
 {
  printf '%s\n' "$@"  \
    | while IFS="" read -r vl; do
       if [[ "$vl" =~ ^[[:space:]]*Wht:[[:space:]]*$ ]]; then
         printf '%s%s%s\n' "${wht}" "$vl" "${rst}"
       elif [[ "$vl" =~ ^[[:space:]]*Grn:[[:space:]]*$ ]]; then
         printf '%s%s%s\n' "${grn}" "$vl" "${rst}"
       elif [[ "$vl" =~ ^[[:space:]]*Blu:[[:space:]]*$ ]]; then
         printf '%s%s%s\n' "${blu}" "$vl" "${rst}"
       else
         printf '%s%s%s\n' "${wht}" "$vl" "${rst}"
       fi
      done
 }

Here is an example

var="
Grn:
  Some lines in green
  More green lites
  Green light again

Blu:
  Now turning to blue
  And more blue"

theone "$var"

The result would be

  Some lines in green
  More green lites
  Green light again

  Now turning to blue
  And more blue

I'm trying to understand what you want. The code looks for `Wht:` (maybe surrounded by whitespace on either side) and if found prints it in what I assume is white text. Similarly green text for `Grn:` and blue for `Blu:`, with a fallback of white text for any other line. So what do you actually want instead of this? Please clarify this in your question - not here as a comment. An example might help (show input data and - as best you can - corresponding output) — roaima, Feb 16 '23 at 23:01
I'm now wondering if you want the `Wht:`, `Grn:`, and `Blu:` to indicate the colour of subsequent text. So they're not to be output but instead used for changing the colour setting — roaima, Feb 16 '23 at 23:04
You are correct on your last comment. Have called `continue` and `break`, but they would not continue to the next line. — Vera, Feb 17 '23 at 09:03
You should read [why-is-using-a-shell-loop-to-process-text-considered-bad-practice](https://unix.stackexchange.com/questions/169716/why-is-using-a-shell-loop-to-process-text-considered-bad-practice) to understand why you shouldn't be using a shell loop for this but instead should be using a text processing tool such as awk. — Ed Morton, Feb 27 '23 at 17:36

roaima · Accepted Answer · 2023-02-18T08:00:58.903

Here's one POSIX-compatible approach to the problem:

#!/bin/sh

# Colour codes
grn=$(tput setaf 2) blu=$(tput setaf 4) wht=$(tput setaf 7)
rst=$(tput sgr0)

theone()
{
    printf '%s\n' "$@" |
        while IFS= read -r vl
        do
            # Strip leading and trailing space
            ns=${vl##[[:space:]]}
            ns=${ns%%[[:space:]]}

            case "$ns" in
                # Look for a colour token
                Wht:)   use="$wht" ;;
                Grn:)   use="$grn" ;;
                Blu:)   use="$blu" ;;

                # Print a line
                *)      printf "%s%s%s\n" "${use:-$wht}" "$vl" "$rst" ;;
            esac
        done
}

If you're using bash you could alternatively put the colour codes into an associative array and look for entries in that instead of using a case … esac construct:

#!/bin/bash

theone()
{
    # Colour codes
    declare -A cc=(
        ['Grn:']=$(tput setaf 2)
        ['Blu:']=$(tput setaf 4)
        ['Wht:']=$(tput setaf 7)
    )
    local rst=$(tput sgr0)

    printf '%s\n' "$@" |
        while IFS= read -r vl
        do
            # Strip spaces
            ns=${vl//[[:space:]]/}

            # Look for a defined token
            if [[ -v cc[$ns] ]]
            then
                # Assign the next colour
                use=${cc[$ns]}
            else
                # Print a line
                printf "%s%s%s\n" "${use:-${cc['Wht:']}}" "$vl" "$rst"
            fi
        done
}

Skip printing on line matching regex pattern

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