25 byte netpbm/shell script polyglot

[deepseagirl]

Entry Info

• Date: 2025-11-02
• BGGP Challenge: 2, 6
• Name: ackmage
• Contact Info:
• Online Presence: herm.it
• Writeup Link: tbd

File Info

• Target File Type: .pbm (netpbm), .sh (shell script)
• Target File Size: 25
• SHA256 Hash: 0973848372fa87c9e05f8f3b5cd8660ef04ae4a832218fd728f78ff66dd1e6a5

File Contents

Please encode the file as Base64

UDEgMyA1IDExMTEwMDExMTEwO2VjaG8gNg==

Environment Info

Target Software and Version

macOS file viewer (Finder)

macOS terminal (or any shell)

Environment Setup

Description of Target Software's Environment (Platform/OS, Setup Instructions, etc.)

macOS Sonoma 14.5

Additional Info

Here attach any additional information about the file, including supporting notes, screenshots, videos, console output, etc.

this file is a polyglot consisting of a netpbm image file and a shell script

to view as a netpbm image, save file and view in Finder:

double-click to open it in Preview:

you really gotta zoooooom in:

to run as a shell script, make executable and run it:

chmod +x 6.pbm
./6.pbm

feel free to test this out on other image viewers and lmk what happens!

[netspooky]

Verified! Thank you!!!

https://github.com/binarygolf/BGGP/blob/main/2025/entries/deepseagirl/deepseagirl.netpbm-shell.md

Verification

• Reviewer: netspooky
• Review Date: 2025-11-22
• SHA256: 0973848372fa87c9e05f8f3b5cd8660ef04ae4a832218fd728f78ff66dd1e6a5
• Score: 4327 (base 4071 + 256 for polyglot challenge)
• Note: Works as is on MacOS. On Ubuntu 24.04 with gnome - Image Viewer complains that the PNM loader expected to find an integer, but didn't. XnViewMP also doesn't have a loader for it.