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I would like to replace strings in a file following this pattern:

  • <<key q>> → <kbd>q</kbd>
  • <<key Ctrl q>> → <kbd>Ctrl</kbd>+<kbd>q</kbd>
  • <<key Ctrl Shift Alt q>> → <kbd>Ctrl</kbd>+<kbd>Shift</kbd>+<kbd>Alt</kbd>+<kbd>q</kbd>

UPDATE: The file contains other text, too. Example: Press <<key Ctrl q>> to quit.

The best solution I could find for this problem is calling sed with separate scripts for 1, 2, 3 and 4 keys:

sed -i -E \
    -e 's|<<key ([^ ]+)>>|<kbd>\1</kbd>|g'
    -e 's|<<key ([^ ]+) ([^ ]+)>>|<kbd>\1</kbd>+<kbd>\2</kbd>|g' \
    -e 's|<<key ([^ ]+) ([^ ]+) ([^ ]+)>>|<kbd>\1</kbd>+<kbd>\2</kbd>+<kbd>\3</kbd>|g' \
    -e 's|<<key ([^ ]+) ([^ ]+) ([^ ]+) ([^ ]+)>>|<kbd>\1</kbd>+<kbd>\2</kbd>+<kbd>\3</kbd>+<kbd>\4</kbd>|g' \
    file.txt

Obviously, this fails for macros containing 5 or more keys.

Is there a more generic solution that works for n keys? Not restricted to sed. I also tried using structural regular expressions (sregx) but couldn't find how to do it.

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3
  • Are Ctrl Shift Alt in your example those literal strings or intended to represent the control characters with those names? Whatever it is, don't use those for an example, just pick 3 other visible characters like X Y Z or 3 unambiguous strings like foo bar etc (whichever you intend to show) and replace those with your real invisible characters or strings when you use the script later. Commented Aug 23, 2022 at 15:57
  • 1
    Yes, Ctrl, Shift and Alt are literal strings. Sorry for using confusing example strings. Next time I'll use foo and bar instead. Commented Aug 23, 2022 at 19:43
  • Regarding UPDATE: The file contains other text, too. Example: Press <<key Ctrl q>> to quit. - don't change your question after you got answers, please roll it back to what it was so as to not invalidate the answers you got. Commented Aug 24, 2022 at 11:50

2 Answers 2

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3

I would go with Perl for such task.

#!/bin/perl
while(<>) {
    if (/<<key (.*?)>>/) {
        my $pattern_with_keys = $1;
        my @keys = split / /, $pattern_with_keys ;
        my @kbd_keys = map {"<kbd>$_</kbd>"} @keys;
        print join('+', @kbd_keys), "\n";
    }
}

Run it with perl script.pl < source_file.txt and enjoy.

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3
  • What if the file contains unrelated text? I think your solution doesn't work for Press <<key Ctrl q>> for foo. If you want bar then press <<key Ctrl Shift Alt q>>.. Commented Aug 23, 2022 at 16:06
  • 2
    @KamilMaciorowski unrelated text can easily be passed through with a perl -pe 's{<<key (.+?)>>}{join "+", map { "<kbd>$_</kbd>" } split /\s+/, $1}eg' form Commented Aug 23, 2022 at 16:39
  • Thanks for your answer! I could accept only one answer but I upvoted both. Commented Aug 23, 2022 at 19:47
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  1. Replace one at a time.
  2. Repeat until no new replacement done.
  3. Remove garbage.

Like this:

sed -E ':start s|(<<key[^>]*) ([^>]*)>>|\1>>+<kbd>\2</kbd>|g; t start; s|<<key>>\+||g'

Where:

  • :start is a label.
  • s|(<<key[^>]*) ([^>]*)>>|\1>>+<kbd>\2</kbd>|g turns <<key Ctrl Shift Alt q>> into <<key Ctrl Shift Alt>>+<kbd>q</kbd>.
  • t start jumps to the label iff s has just substituted anything, so…
  • … <<key Ctrl Shift Alt>>+<kbd>q</kbd> becomes
    <<key Ctrl Shift>>+<kbd>Alt</kbd>+<kbd>q</kbd>, then
    <<key Ctrl>>+<kbd>Shift</kbd>+<kbd>Alt</kbd>+<kbd>q</kbd> and finally
    <<key>>+<kbd>Ctrl</kbd>+<kbd>Shift</kbd>+<kbd>Alt</kbd>+<kbd>q</kbd>. In the next iteration s substitutes nothing (<<key>> does not match because there is no space in it), thus t is a no-op.
  • s|<<key>>\+||g removes remainders.

Note: [^>]* (as opposed to .*) prevents matching across multiple <<key …>> snippets in the same line.

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