Limit Filename Length When Downloading in Ubuntu

Managing file names during downloads is essential for organization and compatibility across different systems. This guide explains how to download files on Ubuntu while controlling or restricting the length of the saved filename. We will cover command-line tools like wget and curl, discuss filesystem limitations, and provide scripts to automatically truncate long names during the download process.

Standard download tools in Ubuntu do not have a built-in flag to automatically restrict filename length based on character count. However, you can control the output name manually or use scripts to enforce limits. The most common filesystem used in Ubuntu, ext4, supports filenames up to 255 bytes. If you need to enforce a shorter limit for compatibility with other systems or personal organization, follow the methods below.

Using Wget with a Specific Name

The most direct way to control the filename is to specify it explicitly using the -O flag. This overrides the remote filename entirely.

wget -O short_name.zip https://example.com/very_long_filename.zip

This method ensures the local file matches your length requirements, but it requires you to know the name beforehand.

Using Curl with a Specific Name

Similar to wget, curl allows you to define the output file using the -o flag.

curl -o short_name.zip https://example.com/very_long_filename.zip

Automating Length Restrictions with a Script

If you are downloading multiple files and want to automatically truncate long filenames to a specific length, you can use a bash script. This script downloads the file using wget and then renames it if the name exceeds a set limit.

Create a file named safe_download.sh:

#!/bin/bash

URL=$1
MAX_LENGTH=50

# Download file allowing wget to choose the name initially
wget "$URL"

# Get the downloaded filename
FILENAME=$(basename "$URL")

# Check length and rename if necessary
if [ ${#FILENAME} -gt $MAX_LENGTH ]; then
    EXTENSION="${FILENAME##*.}"
    NEW_NAME="${FILENAME:0:$MAX_LENGTH}.${EXTENSION}"
    mv "$FILENAME" "$NEW_NAME"
    echo "Renamed to: $NEW_NAME"
else
    echo "Filename OK: $FILENAME"
fi

Make the script executable and run it:

chmod +x safe_download.sh
./safe_download.sh https://example.com/long_filename.zip

Understanding Filesystem Limits

When restricting filenames, ensure you do not exceed the underlying filesystem limits. Ubuntu typically uses ext4, which allows 255 bytes per filename. If you are sharing files with Windows users via Samba or NTFS partitions, note that Windows also has a 255 character limit for paths, though individual filename limits may vary slightly depending on the configuration. Keeping filenames under 100 characters is generally safe for cross-platform compatibility.