Bash Sed Modify all files in directory

#bash #linux #automation #batch

Needed to batch edit the #frontmatter of my markdown files for my Obsidian.md vault.

This script checks if the first line is --- (i.e. the start of frontmatter) and decides if we just add the dg-publish: true or do we need a whole frontmatter block

---
dg-publish: true
---

#!/bin/bash

cd /home/icicle/scripts/test-md

for file in ./*.md; do

  FIRSTLINE=$(head -n 1  "$file")
  SECONDLINE=$(sed -n '2p' "$file")

  ## check if frontmatter already exists
  if [ "$FIRSTLINE" = "---" ]; then

    ## see if "dg-publish: true is already 2nd line"
    if [ "$SECONDLINE" = 'dg-publish: true' ]; then
      echo "Already PUBLISHED: $file"
    else
      sed -i '2i\dg-publish: true' "$file"
    fi
  else
    # add a frontmatter block
    sed -i '1s/^/---\ndg-publish: true\n---\n/' "$file"
  fi

done

MacOS

For #MacOs users use gsed instead of sed

brew install gnu-sed

Credits