oneliner « Narf

I recently had to restore databases from a rough mysqldump backup in a piecemeal fashion. One necessity is to SET the environment correctly, lest some weird encoding issues happen when restoring the data, leading to failures.

A sed one-liner can help for this.

DBNAME=mydb
sed -n "/^-- Server version/,/^-- Current Database/p;/^-- Current Database.*${DBNAME}\`/,/^-- Current Database/{p}" mysqldump.sql > ${DBNAME}.sql

This extracts SQL from the initial header, to the first database, which contains all the sessions SETs. It then captures statements any time the target database is the current one. Note that this doesn’t restore the GRANTs.

Befor blindly piping the output SQL into mysql, one would be well advised to review the contents of the file, to ensure only the desired modifications are included.

GitHub now allows to expand/collapse all files in a PR diff at once (pressing Alt while clicking one of the toggles). Unfortunately, there is no similar feature to mark all files as viewed. This is handy after having reviewed meaningful changes to file, and automatically modified/generated files can be ignored.

So here goes a one-liner for the JS console.

Array.from(document.getElementsByClassName('js-reviewed-toggle')).forEach(c => c.getElementsByTagName('input')[0].checked || c.click())

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Every now and then, some spurious peaks show up on munin graphs. The peaks are order of magnitude higher than the expected range of the data. This particularly happens with DERIVE plugins, that are notably used for network interfaces.

One way to fix this, as suggested by Steve Schnepp (and in the faq), is to set the maximum straight into the RRD database, and then let it reprocess the data to honour this maximum.

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When using syspatch on OpenBSD, the upgrade sometimes fails with

Relinking to create unique kernel... failed!
!!! "/usr/libexec/reorder_kernel" must be run manually to install the new kernel

This generally happens after a system upgrade, or an otherwise manual change of kernel. This fix is to update the kernel hash, before re-running reorder_kernel.

# sha256 /bsd > /var/db/kernel.SHA256
# /usr/libexec/reorder_kernel

Sometimes, one just needs an OAuth access token (for the client credential authentication flow).

export ACCESS_TOKEN=$(curl -X POST \
 --user "${CLIENT_ID}:${CLIENT_SECRET}" \
 --data-urlencode "grant_type=client_credentials" \
 --data-urlencode "scope=${SCOPE}" \
 ${TOKEN_URL} \
 | jp -u access_token)

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I finally mastered the shell (beit bash or zsh, but really, this is readline)’s history with command replacement. It took me 19 years and my entire family fortune to gather enough wits to read that part of the manual with enough attention and will as to learn to use it.

Essentially, you can recall previous commands from the history with !number. You can then change some content of the previous command programmatically before running it by adding :s/PATTERN/REPLACEMENT/ or :gs/PATTERN/REPLACEMENT/ (the first one will replace the first occurrence, the second one will replace them all).

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lpr -P <PRINTER> /usr/share/cups/data/testprint

security export -k /System/Library/Keychains/SystemRootCertificates.keychain -t certs -p

Useful for plain Unix/OpenSSL tools.

With M as the major, m as the minor, and r as the revision,

export M=8 m=65 r=17; wget --no-cookies --header "Cookie: oraclelicense=accept-securebackup-cookie" http://download.oracle.com/otn-pub/java/jdk/${M}u${m}-b${r}/jdk-${M}u${m}-linux-x64.tar.gz

Useful for scripting, headless operation, continuous integration, and just for any time when one doesn’t have any for unneeded account creation.

A screenshot showing URL completion in dmenu

I have parted with FVWM. Not that I was dissatisfied with more than 12 years of using it and organically growing its configuration. I was not.

But I was recently shown i3 which, despite not being Awesome, is indeed awesome. Particularly in the usability of its default, which I found did not require many a tweak. I was however a bit confused at first, then impressed, when I realised that the auto-generated configuration took into account my Dvorak keymap, and updated the keybindings so the keys would be the same as those on a QWERTY keyboard. That’s thoughtfullness.

The next great thing about i3 (save for $mod+Return to start a term anywhere, anytime), is dmenu. At a press of the relevant binding (equivalent to $mod+d on an 200-year-old keymap), one gets to enter a one-line entry where any command can be entered for execution, with incremental completion.

Dmenu is also nice due to its modularity. It takes a list of strings that can be completed on stdin, and outputs the typed or selected string on stdout, for consumption by whatever script called it.

I figured that it should be possible to handle URLs in a dmenu script. It is actually pretty trivial, and the friend who convinced me to take the jump also provided such a script, which would simply open the typed URL. But I wasn’t entirely satisfied, as recent years of browser usage taught me to expect URL completion. So I looked into ways of doing it.

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Narf

The blagosphere got me…

Category Archives: oneliner

Split a multi-DB dump from MySQL/MariaDB

GitHub Pull Request: mark all files as viewed

Removing spurious peaks from munin graphs

Relinking to create unique kernel… failed!

Getting an OAuth access token with cURL

Shell history and modifiers

CUPS: Print a test page from the console

Exporting the SSL root store from Mac OS X’s Keychain

Download Oracle JDK without nagscreens

URL completion in dmenu