Batch Rename Multiple Files with a Specific Pattern

#!/bin/bash

# Configuration
TARGET_DIR="./images" # Directory containing files to rename
OLD_PATTERN="image_"  # Part of the filename to replace
NEW_PATTERN="photo_"  # Replacement part
FILE_EXTENSION="jpg"  # Process only files with this extension (e.g., "png", "txt", "*")
DRY_RUN=true          # Set to 'false' to actually rename files. If 'true', it only prints what it *would* do.

# --- Functions ---
log_message() {
    echo "[$(date +'%Y-%m-%d %H:%M:%S')] $1"
}

# --- Main Script ---
log_message "Starting batch rename operation in $TARGET_DIR..."

if [ ! -d "$TARGET_DIR" ]; then
    log_message "ERROR: Target directory $TARGET_DIR does not exist."
    exit 1
fi

if [ "$DRY_RUN" = true ]; then
    log_message "DRY RUN MODE: No files will actually be renamed. Printing proposed changes."
else
    log_message "LIVE RUN MODE: Files will be renamed."
fi

COUNTER=0
# Loop through files matching the extension
# Using 'find' with '-depth' for safety if renaming directories too, but here focused on files
find "$TARGET_DIR" -maxdepth 1 -type f -name "*.${FILE_EXTENSION}" | while read -r old_path; do
    filename=$(basename "$old_path")
    dirname=$(dirname "$old_path")
    
    # Replace OLD_PATTERN with NEW_PATTERN in the filename
    new_filename="${filename/$OLD_PATTERN/$NEW_PATTERN}"
    new_path="$dirname/$new_filename"
    
    if [ "$filename" != "$new_filename" ]; then
        log_message "Proposed: '$filename' -> '$new_filename'"
        if [ "$DRY_RUN" = false ]; then
            mv "$old_path" "$new_path"
            if [ $? -eq 0 ]; then
                log_message "Renamed: '$old_path' to '$new_path'"
                COUNTER=$((COUNTER + 1))
            else
                log_message "ERROR: Failed to rename '$old_path'."
            fi
        fi
    fi
done

if [ "$DRY_RUN" = false ]; then
    log_message "Renamed $COUNTER files."
fi
log_message "Batch rename operation finished."