Diomidis Spinellis

Professor of software engineering, programmer, technology author. (Tech tweets here. Follow @DSpinellis for Greek/Greece tweets.)

Last Notes

2026-08-29 15:50:03 UTC

Extracting information to aid debugging (here a binary tournament merge failure) can often be productively automated with Unix command-line tools.
awk '$4 == "BEGIN" && $8
{ print $8 " -> " $7}' file.log |
dot -Tsvg >diagram.svg
https://mastodon-acm-org.s3.bhs.io.cloud.ovh.net/media_attachments/files/117/179/545/312/495/983/original/ee67246bb452d1f9.png

2026-05-23 19:06:57 UTC

Have you noticed that reviewing AI-generated code is devilishly hard? Here’s the thing: when working on code with GenAI assistance (from a chat-bot, through IDE auto-completion, or, increasingly, with an AI agent) you need a better understanding of the system than when working without. Cognitive psychology and the workings of large language models give us four clues on why this happens.
https://www.spinellis.gr/blog/20260523/?utm=md260523

2025-12-23 18:38:50 UTC

Several news outlets reported the amazing discovery of a 1970s Fourth Edition Research Unix magnetic tape. I incorporated the tape’s source code into the Unix History Repository hosted on GitHub and studied the code’s composition. Here's what I found.
https://www.spinellis.gr/blog/20251223/?ms261223
https://mastodon.acm.org/system/media_attachments/files/115/770/331/314/686/507/original/c477e19419098312.jpg

2025-11-07 09:43:48 UTC

I just received an AI-generated GitHub pull-request that incorrectly replaced 450 test code lines with a comment. (Of course, all tests passed 😃.) People, be VERY CAREFUL when reviewing out-of-the-blue PRs these days. The AI-generated ones are likely to contain difficult-to-spot faults hidden as plausible fixes.
https://github.com/dspinellis/git-issue/pull/109/commits/d2ab3104643901d4ce5fbca33631fa7e0473df6a
https://mastodon.acm.org/system/media_attachments/files/115/507/724/306/152/350/original/bcc3298623818891.png

2025-10-07 06:28:32 UTC

Following the permanent loss of 858TB data from a South Korea government
datacenter, here's a reminder on the several technologies that are NOT
backup solutions:
RAID, snapshots, Apple Time Machine, cloud storage, availability zone mirroring, database replication, Git/GitHub.
Real backups must to be automatically maintained as multiple encrypted, integrity-checked, tested, monitored, and documented historical copies, on different media, offsite, and offline/immutable.
https://koreajoongangdaily.joins.com/news/2025-10-01/national/socialAffairs/NIRS-fire-destroys-governments-cloud-storage-system-no-backups-available/2412936

2025-05-29 17:57:49 UTC

Wow! The Rust compiler correctly guessed the correct method I should be calling. Helpful and very impressive error handling!
https://mastodon.acm.org/system/media_attachments/files/114/592/405/659/679/817/original/f433501a7a45a861.png

2025-05-27 14:44:21 UTC

In 2023 a fake AI-generated scientific article was falsely attributed to me. I was not the scheme's only victim. My study, just published in the Research Integrity and Peer Review journal, analyzes what going on and who profited from the mass publication of AI-generated articles. https://rdcu.be/enQqG
https://mastodon.acm.org/system/media_attachments/files/114/580/300/873/968/964/original/04e98336d367f170.png
https://mastodon.acm.org/system/media_attachments/files/114/580/301/697/167/254/original/27fdd680f9beb1e8.png

2025-05-02 20:45:20 UTC

Shocking! When I said text should wrap at 72 columns, a student asked what a “column” is. With punched cards and fixed-width font line / dot matrix printers fading into history, the idea of a text column doesn't seem to be obvious anymore.
https://mastodon.acm.org/system/media_attachments/files/114/440/186/393/699/384/original/64a03a0f5d9d24f0.jpg
https://mastodon.acm.org/system/media_attachments/files/114/440/186/878/903/756/original/05bfc7a26d989b25.jpg
https://mastodon.acm.org/system/media_attachments/files/114/440/187/393/991/851/original/ad8264471fc6c4b5.jpg

2025-04-24 19:48:32 UTC

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@nprofile…6m2n
HISTSIZE controls the number of in-memory entries, HISTFILESIZE the history file's entries. HISTIZE sets HISTFILESIZE if this isn't specified. Set it to -1 to get unlimited history.
I save all history and I can retrieve a command I entered several years ago.
https://mastodon.acm.org/system/media_attachments/files/114/394/665/960/288/680/original/fdb6c84414fb23c2.png

2025-04-11 03:59:35 UTC

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@nprofile…59k6 Transistors can degrade and fail due to electromigration and charge trapping . Also the devices you mention aren't entirely "solid state". Electrolytic capacitors are a major part of the problem. See https://en.wikipedia.org/wiki/Transistor_aging and https://en.wikipedia.org/wiki/Capacitor_plague

2024-05-10 09:02:47 UTC

Which general-purpose / domain-agnostic tool would you recommend to execute tasks based on dependencies between them?

2024-02-04 17:36:08 UTC

I love curl and ai-cli-lib! https://github.com/dspinellis/ai-cli-lib
https://mastodon.acm.org/system/media_attachments/files/111/874/416/933/012/187/original/f71a123d4a9ae2ff.png