Make an index or table of contents in a markdown document

Problem:

I need to make an index or Table of Contents in a markdown document. For every: ## My title I have to make a link: My title

Solution:

To buil it automatically, you can use an awk script.

Step by step:

Option 1. Execute the script directly in Terminal.

1. Open a Terminal and type the awk script:

   awk '$0 ~ /^## / {gsub(/^## /,"",$0); gsub(/ $/,"",$0); mytitle=$0; $0=tolower($0);  gsub(/\(|\)|\[|\]|\/|\:|\./,"",$0);    gsub(/ /,"-",$0);    print "["mytitle"]""(#"$0")" }' mydatafile.md
   

2. The last awk script get list of links: every link in a new row. If you want a list comma separated you can execute this script:

   awk '$0 ~ /^## / {gsub(/^## /,"",$0); gsub(/ $/,"",$0); mytitle=$0; $0=tolower($0);  gsub(/\(|\)|\[|\]|\/|\:|\./,"",$0);    gsub(/ /,"-",$0);    print "["mytitle"]""(#"$0")" }' mydatafile.md | awk '{acumulador=acumulador", "$0}END{print substr(acumulador,3)}'
   

Option 2. Create awk files and then execute them from Terminal.

1. Create the file make-index-links.md with these lines:

   #/bin/bash/awk
   $0 ~ /^## / {gsub(/^## /,"",$0); gsub(/ $/,"",$0); mytitle=$0; $0=tolower($0);  gsub(/\(|\)|\[|\]|\/|\:|\./,"",$0);    gsub(/ /,"-",$0);    print "["mytitle"]""(#"$0")" }
   

2. Create the file replace-newline-for-comma-and-space.awk with these lines:

   #/bin/awk
   {acumulador=acumulador", "$0}END{print substr(acumulador,3)}
   

3. Execute from Terminal:

   awk -f make-index-links-in-markdown.md mydatafile.md | awk -f replace-newline-for-comma-and-space.awk 
   

Source:

https://www.gnu.org/software/gawk/manual/gawk.html
https://www.gnu.org/software/gawk/manual/html_node/String-Functions.html