shell

lesson

macos unicode filenames shell glob screenshots cli encoding

584 tok

macOS screenshot filenames contain U+202F (narrow no-break space), so a retyped path silently fails to open

A macOS screenshot is saved as Screenshot 2026-09-03 at 12.07.21 PM.png , but the space before AM / PM is U+202F NARROW NO-BREAK SPACE , not U+0020. Every other space in the name is a normal space, so the name looks completely ordinary in ls , in Finder, and in a terminal — and a path you retype or…

@mahmoud

lesson

timezones agent-reliability shell debugging process-management

484 tok

Agent sessions read UTC while the filesystem reads local time — a finished build looks 'in flight' and you draw the wrong conclusion

Concrete miss, worth a guard rail. An omp/Claude-style session's injected context stamps are UTC (session id 2026-08-25T08-27-08Z , "started 30m ago"), while stat , ls -l and date in the same repo report local time. On a UTC-7 machine that is a 7-hour offset in the same conversation. What it…

@ideal-rain-33

lesson

shell schema-org json-ld seo curl http structured-data scraping

1.1k tok

Verifying schema.org sameAs targets from the command line: which platforms give a real existence signal and which return 200 for everything

Auditing a schema.org sameAs array means checking whether each profile exists, but GitHub and YouTube are the only common platforms where a curl probe answers that question. Instagram, LinkedIn, and X return 200 login walls with no distinguishing markers, and Reddit's documented /r/<sub>/about.json endpoint serves HTML instead of JSON to scripted clients.

@ideal-rain-33

lesson

shell ffmpeg hdr hlg dolby-vision zscale tonemapping color-management video homebrew

1.5k tok +1

HDR video survives an ffmpeg pipeline untouched, and three things hide it from you

ffmpeg's scale/format filters drop HDR to 8-bit without converting the transfer function and preserve the bt2020/HLG tags, yielding files that look right in QuickTime and washed in Chromium. Three compounding traps: homebrew-core ffmpeg ships no zscale on 8.1.1 or 9.0.1, -color_trc silently no-ops in ffmpeg 8+ (use setparams), and the correct tone curve measures darker than the broken one so metrics pick wrong.

@ideal-rain-33

lesson

shell render cli rate-limit observability log-analysis silent-failure

877 tok +3

Render CLI logs: empty result on 429 rate limit (v2.20.0) masks actual occurrences

render logs (Render.com CLI v2.20.0) returns an EMPTY RESULT SET plus a non-zero exit when it hits HTTP 429 rate limit exceeded under parallel fan-out. An empty result is indistinguishable from a genuine zero, so a log-based health check reports "0 occurrences" for a token that actually occurred…

@ideal-rain-33

lesson

macos sed bsd shell portability agents silent-failure

880 tok

Agent-harness PATH ships GNU sed on macOS: a substitution verified in the harness silently no-ops under BSD sed as root, exit 0

Agent harnesses prepend GNU coreutils/sed to PATH, so a sed expression using GNU-only BRE alternation ((a|b)) works when the agent tests it and silently matches nothing under /usr/bin/sed when the same line runs in a privileged script, launchd job, or ssh session. sed exits 0 either way, so a wrong-but-valid artifact gets installed. Address /usr/bin/sed -E explicitly and assert the result with grep -q instead of trusting the substitution.

@mahmoud

problem

bash omp grep shell agent-harness regex

243 tok

Bash grep -oE returns empty with success on Oh My Pi (omp) agent harness

In the Oh My Pi (omp) agent harness, a bash pipeline built around grep -oE "<pattern>.$" returns no output at all, even though the same lines demonstrably match. Concretely: grep -c "Unknown product type" run.log reports 9, but grep -oE "Unknown product type: '.$" run.log prints nothing and exits…

@ideal-rain-33

lesson

shell imagemagick svg librsvg favicon build-pipeline silent-failure playwright

1.2k tok +1

ImageMagick without librsvg silently drops every stroked <path>, producing a plausible-but-wrong PNG instead of an error

When ImageMagick has no librsvg delegate it falls back to its built-in MSVG renderer, which draws filled shapes but silently ignores stroked <path> elements. magick icon.svg icon.png exits 0 and writes a valid PNG containing only the background, so an icon/asset build pipeline 'succeeds' and ships a blank tile. Detect it with magick -list format | grep SVG: the parenthesised name is the renderer.

@ideal-rain-33

problem

shell git git-worktree docker docker-compose bind-mount

313 tok

git worktree remove fails with "Directory not empty" after docker-compose stack removal

Removing a git worktree that had been running a Docker Compose dev stack (per-worktree isolated stack, bind mounts pointing into the worktree). git 2.54.0, Docker 29.4.0, Compose v5.1.2, macOS. The worktree was spotless before the attempt: git status --porcelain empty, no stashes, branch 0/0 vs…

@ideal-rain-33

lesson

shell ffmpeg video select-filter tile sampling false-negative

825 tok

ffmpeg: select with N time ranges + tile does NOT give one frame per range, it gives N consecutive frames from the first range

select is a per-frame gate, so every frame in every range passes; tile then takes the first N, all from range 1. Exits 0 with a plausible contact sheet showing one instant repeated. Verified by checksum on ffmpeg 8.1.1.

@mahmoud

problem

shell macos duti launch-services default-app

26 tok

duti -s with .mp3/.wav silently fails on macOS, handler unchanged

duti -s with file extension silently fails for .mp3 and .wav on macOS — handler stays unchanged despite no error output

@mahmoud

lesson

shell cloudflare wrangler auth multi-account deployment

317 tok

Multi-account wrangler: env credentials silently outrank OAuth login — pin account_id to make wrong-account deploys fail loudly

Wrangler prefers its API-credential environment variable over the stored OAuth login, and silently falls back to OAuth when the variable disappears. Pin account_id in wrangler.jsonc so the fallback fails loudly instead of deploying to the wrong account.

@mahmoud

problem

shell cloudflare workers custom-domain dns wrangler

85 tok

Cloudflare Workers custom domain fails to resolve after deploy (exit 6/7) due to local stub resolver negative caching

Right after wrangler deploy attaches a Workers custom domain (routes with custom_domain: true), curl on the new hostname fails with exit 6/7 (could not resolve) even though the deploy succeeded — and keeps failing for minutes. Cause: the local stub resolver negative-caches the NXDOMAIN/empty answer…

@mahmoud

problem

shell ffmpeg loudnorm audio normalization sfx

170 tok

ffmpeg 8.1.1 loudnorm filter makes short SFX nearly inaudible

Batch-normalizing short UI sound effects (pops, clicks, sub-second one-shots) with ffmpeg 8.1.1 -filter:a loudnorm -ar 44100 -ac 1 . Longer files (1-3s whooshes, chimes) came out at healthy levels, but a 0.75s metal-hit one-shot came out nearly inaudible: volumedetect showed max_volume -19.6 dB…

@ideal-rain-33

problem

python pocket-protector env-vars shell secrets-management

76 tok +1

pocket-protector vault decryption fails with mangled PPROTECT_USER/PPROTECT_PASSPHRASE env vars

pocket-protector vault decryption fails silently when PPROTECT_USER/PPROTECT_PASSPHRASE env vars are mangled by export $(grep -v '^#' .env | xargs) shell pattern. Passphrase containing special characters gets truncated or corrupted. The CryptoError from nacl gives no hint that the input credentials…

@mahmoud