Okay. To address the %20 and the https links, and the placeholder links, I came up with a bash script to handle this.

Because of the variation in the links, instead of trying to write a sed command that will match only %20 in anchor markdown links, and placeholder links, while ignoring https links and ignoring all other text in the document.

To do that, I used grep, a while loop, IFS, and sed

Here’s the script:

#! /bin/bash

mdlinks="$(grep -Po ']\((?!https).*\)' ~/mkdn"

while IFS= read -r line; do
	dashlink="$(echo "$line" | sed 's/%20/-/g')"
	sed -i "s/$line/${dashlink}/" /path/to/file
done <<<"$mdlinks"

I’m not sure how familiar you are with bash scripting, so I’ll do the same breakdown:

#! /bin/bash - This tells the shell what interpreter to use for the script. In this case it’s bash.

mdlinks="$(grep -Po ']\((?!https).*\)' /path/to/file" - This line uses grep to search for markdown link enclosures excluding https links and to output only the text that matches and saves all of that into a variable called mdlinks. Each link match will be a new line inside the variable.

The breakdown of the grep command is as followes:

grep - invokes the grep command

-Po - two command flags. The P tells grep to use perl regular expressions. The o tells grep to only print the output that matches, rather than the entire line.

' - opens the regex statement

]\( - finds a closing bracket followed by an opening parentheses

(?!https) - This is a negative look ahead, which a feature available in perl regex. This tells grep not to match if it finds the https string. The parentheses encloses the negative look ahead. The ?! Is what indicates it’s a negative look ahead, and the https is the string to look for and ignore.

' - closes the regex statement

/path/to/file - the file to search for matches

while IFS= read -r line; do - this invokes a while loop using the Internal Field Separator (IFS=), which by default includes newline character. This allows the loop to take in the variable containing all of the matched links and separate them line by line to work on one at a time. The read command does what it says and reads the input given. In this case our variable mdlinks. The -r flag tells read to ignore the backslash character and just treat it as a normal part of the input. line is the variable that each line will be saved in as they are worked through the loop. The ; ends while setup, and do opens the loop for the commands we want to run using the input saved in line.

dashlink="$(echo "$line" | sed 's/%20/-/g')" - This command sequence runs the markdown link saved in the line variable into sed to find all instances of %20 and replace them with a -.

dashlink - the variable we’re saving the new link with dashes to.

= - separates the variable from the input being saved into the variable.

" - opens this command string for variable expansion.

$ - tells bash to do command substition, meaning that the output of the following commands will be saved to the variable, rather than the actual text of the commands that follows.

( - opens the command set

echo - prints the given text or arguments to standard output, in this case the given argument is the variable $line

" - tells bash to expand any variables contained within the quote set while ignoring any nonstandard characters like spaces or special shell characters that are saved in the variable.

$line - the variable containing our active markdown link from the text document

" - the closing quote ending the argument and the expansion enclosure

| - This is a pipe, which redirects the standard output of the command on the left into the command on the right. Meaning we’re taking the markdown link currently saved in the variable and feeding it into sed

sed - invokes sed so we can manipulate our text, and because sed is receiving redirected input, and we’ve specified no flags, the modified text will be printed to standard output.

's/%20/-/g' - Our pattern match/substitution, which will find all occurrences of the string %20 in the markdown link fed into sed and replace them with -.

)" - closes our command sequence for command substitution, and the variable expansion. At this point the text printed to standard output by sed is saved to the variable dashlink

The next line is: sed -i "s/$line/${dashlink}/" /path/to/file, which uses sed to take the line and dashlink variables and use them to find the exact original markdown link in the text containing the %20 sequences, and replace it with the properly formatted markdown link with dashes.

sed -i - invokes sed and uses the -i flag to edit the file in place.

" - The double quote enclosure allows the expansion of variables in the pattern match/replacement sequence so it searches for the markdown link, and not the literal text string $line.

s/ - opens our match/modify sequence.

$line - the original markdown link that will be found

/ - ends the pattern matching section

${dashlink} - The variable containing the previously modified markdown link that now has dashes. This expands to that properly formatted link which will be written into the text file replacing the malformed link. I don’t know why this link has to be enclosed in curly braces while the first one does not.

/" - ends the text modification section and closes the variable expansion.

/path/to/file - the file to be worked on

Finally we have done<<<"$mdlinks", which ends the while loop and feeds the mdlinks variable into it.

done - closes the while loop

<<< - This feeds the given argument into the while loop for processing

" - expands the variable within while ignoring nonstandard characters

$mdlinks - the variable we’re feeding in with all of our links containing %20, except for https links.

" - closes the variable expansion.

If you’ve never written/created your own bash script, here’s what you need to do.

• in your home directory, or in the directory you’re working in with these files, use a text editor like vim or nano or gedit or kate or whatever plain text editor you want to to create a new file. Call the file whatever you want.

• Paste the entirety of the script text into the file. Modify the file paths as needed to work the file you want to work. if working multiple files, you’ll need to update the script for each new file path as you finish one and move on to the next

• Save and exit the file

• Make the file executable at the terminal with sudo chmod +x /path/to/script/file

• To run it:

  • Change directory to the directory that contains the script file (if you’re not already there)
  • at the command line use the command . ./name-of-script-file

Don’t worry or apologize about your English. I’m having no trouble understanding. :)

I’m going to take the second part first and come back with another comment to address the %20 and https bits.

So these variations, like [1.3 Subtitles](BDMV_svt-av1_encode_anime.md#1.3%20Subtitles), are where you would start to craft a new expression. Trying to catch every variation in a single expression would get to complicated and more likely to fail and/or modify text you don’t want modified.

So in this case, here’s the expression I’d use:

sed -ri 's|(]\(.+[0-9]+)\.([0-9]+.+\))|\1-\2|' somefile

And the breakdown:

sed -ri calls sed with the expanded regular expressions capabilities and to edit the file in place

's| - Begins the pattern match|modify expression

( - This very first opening parentheses is a special metacharacter that is used to group a sub-expression within the larger expression. By doing this we can create variables that we can refer to in the modification portion of the command.

]\( - Find the closing bracket character and an opening parentheses character, which we know will be the beginning of a markdown url. The backslash precedes the open parentheses to escape it and indicate it needs to look for the actual open parentheses character

.+ - Find any character (indicated by the .) one or more times (indicated by the +). This will find any characters until it gets to the next specified character in the expression

[0-9]+ - This is two parts. The first part is [0-9]. The brackets are metacharacters in regex that enclose a character set to match from. In this case the character set is the numbers zero to nine. What this means on its own is that sed will look for one occurrence of any number between zero and nine. The + tells sed to find one or more occurrences of a number between one and nine until it gets to the next portion of the pattern. I did this because I don’t know the upper bounds of the documentation numeration you’re working with in the links. If all the links only contain single digit numbers before the decimal, you can remove the +.

) - This closing parentheses marks the end of the subexpression that we want to refer to. In this case, the sub expression is capturing from the closing bracket up to (but not including) the decimal in the number.

\. - This tells sed to find the period/dot/decimal character in the number. It’s preceded by the backslash because the period/dot/decimal character is a metacharacter in regular expressions.

( - This is the beginning of a new subexpression

[0-9]+ - The numeral capture repeats to find the number after the period/dot/decimal. Similarly to the number before the decimal, if the number after the decimal is only ever single digit, the + can be removed.

.+ - Find any character (indicated by the .) one or more times (indicated by the +). This will find any characters until it gets to the next specified character in the expression, taking us to the end of the url

\) - Find the closing parentheses of the url. The backslash precedes the closing parentheses to escape it and indicate it needs to look for the actual open parentheses character.

) - This closes our second subexpression, which captures everything from the number after the decimal to the closing parentheses of the link.

| - Indicates the end of the pattern matching portion of the expression/command. and the beginning of the modification part of the command/expression.

\1 - This is how we refer to or call the subexpressions. The syntax is a backslash followed by a number, and the number indicates the sequential position of the subexpression. So \1 refers to this portion of the regex in the command above: (]\(.+[0-9]+). This section of the expression is capturing everything from the closing bracket up to (but not including) the period/dot/decimal character. By using it in this position in the substitution/modification, we’re just using it as a variable, so in the substitution, it’s going to put everything it finds in the first subexpression first in the new/modified string of text.

- - This tells sed to put a dash immediately after the first subexpression in this new/modified string of text, effectively replacing the period/dot/decimal in the number portion of the url.

\2 - This is calling the second subexpression, which is this portion of the pattern matching regex: [0-9]+.+\). This captures everything in the url from the number after the period/dot/decimal (not including the decimal), to the closing parthenses of the markdown url. Used in this position of the substitution it tells sed to place it after the dash in the new/modified text.

|' - This indicates the end of the modification portion of the command and closes the match|substitution expression.

somefile - The file to be worked on

Here is the full command again: sed -ri 's|(]\(.+[0-9]+)\.([0-9]+.+\))|\1-\2|' somefile

Altogether what this does is: Begin the first subexpression that starts with finding a closing bracket followed by an opening parentheses followed by any character one or more times until finding at least one or more numbers between zero and nine until it finds a decimal, and then close and remember what was found for this sub expression (not including the decimal). Then begin the second subexpression that starts with finding a number between zero and nine one or more times, and then find any character any number of times until a closing parentheses is found. Then close and remember what was found in this subexpression. Replace everything with subexpression one followed by a dash followed by subexpression two.

If you also need this markdown link text to be converted to lowercase, just add \L to the replacement section before the \1 like so:

sed -ri 's|(]\(.+[0-9]+)\.([0-9]+.+\))|\L\1-\2|' somefile

Quick question as I’m working on this, in the new link example, is the BDMV and other capitalized text in this link supposed to be converted to lowercase, or to remain uppercase?

Edit: expanded the question to question case in the whole link