Modifying Files while Preserving Timestamps

Properties2

Type	Practice
Note created	Jan 22, 2026

When modifying files programmatically (e.g., with sed), the file’s modification timestamp is updated automatically. This can be problematic when the modification date carries semantic meaning, such as in Obsidian vaults where notes are sorted by modification time.

A possible approach, in macOS:

1. Save the original modification time using stat
2. Modify the file
3. Restore the original modification time using touch

# Save original modification time (macOS format)
mod_time=$(stat -f "%Sm" -t "%Y%m%d%H%M.%S" "$file")
 
# Modify the file (example: replace text with sed)
sed -i '' 's/old_text/new_text/' "$file"
 
# Restore the original modification time
touch -t "$mod_time" "$file"

A full example is:

#!/usr/bin/env bash
 
for file in *.md; do
  # Save original modification time
  mod_time=$(stat -f "%Sm" -t "%Y%m%d%H%M.%S" "$file")
  
  # Modify the file
  sed -i '' 's/old_pattern/new_pattern/' "$file"
  
  # Restore the original modification time
  touch -t "$mod_time" "$file"
  
  echo "Modified: $file"
done