Batch Rename Files with a Pattern or String Replacement

#!/bin/bash

# Configuration
SEARCH_STRING="old_prefix_"
REPLACE_STRING="new_prefix_"
TARGET_DIR="./assets"

# Ensure the target directory exists
if [ ! -d "$TARGET_DIR" ]; then
  echo "Error: Target directory '$TARGET_DIR' does not exist." >&2
  exit 1
fi

echo "Scanning '$TARGET_DIR' for files to rename..."

COUNT=0
# Loop through all files in the target directory
# Adjust '*.jpg' or '*' to match specific file types or all files
for filepath in "$TARGET_DIR"/*;
do
  # Check if it's a regular file and not a directory
  if [ -f "$filepath" ]; then
    filename=$(basename "$filepath")
    
    # Check if the filename contains the SEARCH_STRING
    if [[ "$filename" == *"$SEARCH_STRING"* ]]; then
      # Perform string replacement
      new_filename=$(echo "$filename" | sed "s/${SEARCH_STRING}/${REPLACE_STRING}/g")
      new_filepath="$TARGET_DIR/$new_filename"
      
      if [ "$filename" != "$new_filename" ]; then
        echo "Renaming: '$filename' to '$new_filename'"
        mv "$filepath" "$new_filepath" || {
          echo "Error: Failed to rename '$filename'." >&2
        }
        ((COUNT++))
      fi
    fi
  fi
done

echo "
Finished renaming. Total files renamed: $COUNT."