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| -rw-r--r-- | LICENSE.markdown | 23 | ||||
| -rw-r--r-- | README.markdown | 25 | ||||
| -rwxr-xr-x | doomsh | 137 |
3 files changed, 185 insertions, 0 deletions
diff --git a/LICENSE.markdown b/LICENSE.markdown new file mode 100644 index 0000000..e55879c --- /dev/null +++ b/LICENSE.markdown @@ -0,0 +1,23 @@ +MIT License +=========== + +Copyright (c) 2016 Tom Ryder + +Permission is hereby granted, free of charge, to any person obtaining a copy of +this software and associated documentation files (the "Software"), to deal in +the Software without restriction, including without limitation the rights to +use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies +of the Software, and to permit persons to whom the Software is furnished to do +so, subject to the following conditions: + +The above copyright notice and this permission notice shall be included in all +copies or substantial portions of the Software. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE +SOFTWARE. + diff --git a/README.markdown b/README.markdown new file mode 100644 index 0000000..0ab49d1 --- /dev/null +++ b/README.markdown @@ -0,0 +1,25 @@ +doomsh +====== + +Use ulimit to severely restrict your Bash shell's resources, and see how long +you can last before segfaulting or giving up. + +Not really important or useful in any way, but kind of fun to see what breaks +when resources are really tight, especially when it exposes problems in +programs like failing to check for NULL returns from malloc(3). + +On the author's machine, at level 5, even ls(1) doesn't work, let alone Vim. + +If you're really crazy, you'll try and launch X processes from it, and watch +them twitch as they die. + +READ THE LICENSE. THE AUTHOR WAIVES ALL RESPONSIBILITY FOR ANYTHING THIS DOES +DO TO YOUR COMPUTER, YOUR DATA, OR YOUR DOG. + +Author +: Tom Ryder +Copyright +: 2016 +License: +: MIT (see LICENSE.markdown) + @@ -0,0 +1,137 @@ +#!/usr/bin/env bash + +# +# doomsh: Play with low ulimits in Bash +# +# Author: Tom Ryder +# Copyright: 2016 +# License: MIT (see LICENSE.markdown) +# +self=doomsh + +# Don't try to play doomsh if already playing doomsh +if [[ $DOOMSH ]] ; then + printf '%s: Already playing doomsh!\n' \ + "$self" >&2 + exit 2 +fi + +# Show the coloured logo; thanks to Frans P. de Vries for the classic ASCII art +# <http://www.gamers.org/~fpv/doombann.html> +printf >&2 %s "$( { + tput AF 3 || tput setaf 3 + tput md || tput bold +} 2>/dev/null )" +while IFS= read -r line ; do + printf >&2 '%s\n' "$line" +done <<EOF +______ _____ _____ __ ___ +| __ \ _ | _ | \ / | +| | \ | | | | | | | . V . | +| | / | \_/ | \_/ | |\ /| | +| |/ / \ / \ /| | V | | +| ' / \_/ \_/ \_| | | +|__/ \_| +EOF +printf >&2 %s "$( { + tput me || tput sgr0 +} 2>/dev/null )" + +# Need to figure out a skill level +declare -i skill + +# If we have an argument, that must be the skill level +if (($#)) ; then + skill=$1 + shift + +# Otherwise, we'll give the user a menu to choose from +else + while IFS= read -r line ; do + printf >&2 '%s\n' "$line" + done <<EOF + +1. I'm too young to die +2. Hey, not too rough +3. Hurt me plenty +4. Ultra-Violence +5. Nightmare! + +EOF + read -er -p '[1-5]: ' skill + + # If the user chose "Nightmare!" mode, get them to confirm, in the true + # spirit of things; otherwise, quit + if ((skill == 5)) ; then + while IFS= read -r line ; do + printf '%s\n' "$line" >&2 + done <<EOF + +Are you sure? This skill level isn't even remotely fair. +EOF + read -er -p '[y/N]: ' confirm + [[ $confirm == [Yy]* ]] || exit 1 + fi +fi + +# Don't accept any other skill level settings +case $skill in + 1|2|3|4|5) + ;; + *) + printf '%s: Unknown skill level\n' \ + "$self" >&2 + exit 2 +esac + +# Form a red prompt (hopefully) using terminal escapes +ps1=$(printf '%sdoomsh[%u]\$%s ' \ + "$( { + tput AF 1 || tput setaf 1 + } 2>/dev/null )" \ + "$skill" \ + "$( { + tput me || tput sgr0 + } 2>/dev/null )" +) + +# Set the limits based on the skill level +declare -i filesize files stack memory +filesize=$((1 << (8 - skill))) +files=$((11 - skill)) +stack=$((1 << (11 - skill))) +memory=$((1 << (19 - skill))) + +# Display the limits +printf >&2 '\n' +printf >&2 'File size writing limit: %u blocks\n' \ + "$filesize" +printf >&2 'Open files limit: %u\n' \ + "$files" +printf >&2 'Stack size: %u kbytes\n' \ + "$stack" +printf >&2 'Memory size: %u kbytes\n' \ + "$memory" +printf >&2 '\n' + +# Record the current seconds since shell start, so we can tell how long the +# user lasts before giving up or segfaulting +declare -i start +start=$SECONDS + +# Open a subshell so that the ulimit settings don't persist after the fork +( + # We only proceed if the ulimit call succeeds + ulimit \ + -f "$filesize" \ + -n "$files" \ + -s "$((1 << (10 - skill)))" \ + -v "$((1 << (19 - skill)))" \ + || exit 2 + DOOMSH=$skill PS1=$ps1 bash --norc +) + +# Give the user some statistics about their performance +printf >&2 '%s: You lasted %u seconds at skill level %u!\n' \ + "$self" "$((SECONDS - start))" "$skill" + |