awk explainer example

awk0.sh

# General pattern
# 
# awk '
#     BEGIN { a1; a2; a3; }
#     <pattern> { a1; a2; a3; }
#     END { a4; a6; }
# ' <filename>

# space - default file separator
# $0 - entire line
# $1 - word 1
# NR - number of records (line number - starts at 1
# NF - number of fields


awk '
  BEGIN { n = 0; }
  {
     if ($0 = "---") {
        if (n == 1) {
           print "xxx";
        } else {
          print;
        }

        n+=1;
       
     } else {
        print;
     }
  }
' <filename>

awk1.fish

for f in *.md
  
  awk -i inplace -v filename="$f" '
    BEGIN { n = 0; }
    {
       if ($0 = "---") {

          if (n == 1) {
            sub(".md", "/", filename)

            sub("-", "/", filename)
            sub("-", "/", filename)
            sub("-", "/", filename)

            print "redirect_from:\n   - /"filename;
            print "xxx";
          } else {
            print;
          }

          n+=1;

       } else {
          print;
       }
    }
  ' $f
end