Firefox blocks certain clipboard events by default. This breaks some Google Docs functionality. To reenable it, go to about:config and set dom.event.clipboardevents.enabled to true
Please be aware that this is a global setting and allows all websites access to your clipboard, which is a potential privacy/security risk.
Monday, September 21, 2020
Prevent Gentoo Portage from unmerging kernel sources during a world upgrade
Portage typically unmerges all but the newest kernel sources, while I'd prefer to leave the sources to the running kernel and backup kernel installed. I don't reboot very often and I don't bother to build an updated kernel until I'm ready to reboot, just in case there are any issues. I also like to keep the sources to the previous kernel around just in case I need to revert.
First, define a kernel set in /etc/portage/sets.conf:
[kernels] class = portage.sets.dbapi.OwnerSet world-candidate = False files = /usr/src
Tthen add the @kernel set to your /var/lib/portage/world_sets file.
By doing this, you will need to manually unmerge the specific kernel source packages you want to remove, but none of them will ever be removed otherwise.
Determining the manufacturer and recording medium of a blank CD or DVD
Every recordable CD and DVD actually has a little bit of data on the blank disc. On CDs this is called the ATIP (Absolute Time in Pregroove) and contains things like the manufacturer, length, dye type, and rated speed. This information is used by the disc drive to choose the optimal burning strategy.
Keep in mind this info can be faked (Hong Kong manufacturers putting fake TY01 codes on their discs was a thing when Taiyo Yuden discs were in high demand). And the dye type is not necessarily the actual dye type used, but the hint to the drive about which burning mode to use (I've read that azo discs are burned using the cyanine strategy).
To view the atip of a CD-R/CD-RW on Linux using the cdrecord package:
# cdrecord -atip
Recordable DVDs have a similar area called the Media Identification Code. To read this information on Linux using the dvd+rw-tools package:
# dvd+rw-mediainfo /dev/sr0
SQL: Get just the date part of a DATETIME on SQL Server 2005
In Microsoft SQL Server 2008+ there is a DATE type, and getting just the date portion of a DATETIME is as easy as a cast or convert to DATE. But, at my job, we're still using SQL Server 2005. What then?
A common technique is to cast to a float, which gives you a number where the part to the left of the decimal point is the date and the part to the right of the decimal point is the time. Wrap that in a FLOOR function to round down to the nearest whole number and you have effectively truncated the time portion. You can then cast that back to a DATETIME.
I have, however, read that doing it that way can be inefficient as it won't use DATETIME indexes. Another approach that it supposed to be more efficient is to use DATEADD and DATEDIFF like so:
1 | SELECT DATEADD([dd], 0, DATEDIFF([dd], 0, GETDATE())); |
Again, there is no reason to do that unless you are on a Microsoft SQL Server version prior to 2008.
Easily straighten a crooked scan or photo in GIMP
To easily straighten a crooked scan or photo in GIMP, don't bother with manual rotation and rulers. Just use the Measure tool (Shift-M) and draw a line along a straight edge or horizon line of your image. Then click the "straighten" button and it will rotate the image to match the line you just drew.
Determining where a CD or DVD was manufactured
On factory-pressed CDs (and some DVDs), on the shiny side of the disc near the center spindle ring there is usually text, known as the matrix string. Old vinyl records usually had writings in the same area. You can sometimes determine where a disc was mastered or pressed by the text contained in this area. For example a music CD with the text "EMI JAX" was manufactured at EMI's manufacturing plant, located in Jacksonville, Illinois, just west of Springfield. Additionally there are sometimes text stamped or etched into the plastic mould such as "MADE IN USA BY PMDC" (indicating the disc was made by PolyGram Manufacturing And Distribution Centers in Grover, North Carolina). A search for the text on Discogs will usually yield useful information.
There was no standard to how any of that text was formatted and often it was not obvious where the disc was made. Beginning in 1994, Philips and the International Federation of the Phonographic Industry created a system of markings called a SID code (Source Identification). The goal of this was to be able to trace a disc back to its origins to fight piracy/counterfeiting. The SID code always begins with the letters "IFPI" followed by a 4- or 5-digit code. There are two types of SID codes. The matrix SID code (present in the matrix area of the disc) identifies where the glass master of the disc was cut. The Mould SID code (in the plastic area) identifies where the disc was pressed/stamped.
The most thorough list of SID codes I have found is on the Musik-Sammler wiki though again a search of Discogs often also provides clues.
Because of consolidation, a decline in CD sales and an increase in DVD sales, the disc pressing plants changed ownership quite often during the 90s and early 2000s. By identifying the codes or matrix text on your disc, it can help you narrow down when it was actually manufactured and whether it is an original release or a repress/reissue from later years. Sometimes the artwork and copyright dates are identical and the only difference the original pressing and a later reissue is on the matrix/SID codes.
There are pressing plants in Russia and China and other places that do not conform to this standard, so the lack of SID code does not automatically mean the disc is from before 1994. But the presence of one means it is surely no older than 1994.
SQL: TRY_CAST alternative for old versions of SQL Server
In modern versions of Microsoft SQL Server there is a TRY_CAST function which returns NULL if the type cast fails, and returns the converted value if it succeeds. This is helpful if you're trying to format numbers from non-sanitized input and somebody put malformed data into a field.
At my job, I'm still dealing with SQL Server 2005 which does not provide this function. An alternative that I found online was to use XML to accomplish the same result:
1 | CAST('' AS XML).value('sql:column("ItemHeight") cast as xs:decimal ?', 'decimal(28,10)') |
SQL: Replace repeated spaces with a single space
In SQL dialects that provide a REPLACE function you can replace instances of repeated spaces with a single space (you may replace CHAR(7) with another character that you know won't appear in your dataset):
1 | SELECT REPLACE(REPLACE(REPLACE('some string with many spaces', ' ', ' ' + CHAR(7)), CHAR(7) + ' ', ''), ' ' + CHAR(7), ' '); |
Rosetta Code
Rosetta Code is a programming chrestomathy site. The idea is to present solutions to the same task in as many different languages as possible, to demonstrate how languages are similar and different, and to aid a person with a grounding in one approach to a problem in learning another.
For example, to calculate the Fibonacci sequence in ArnoldC:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | IT'S SHOWTIME HEY CHRISTMAS TREE f1 YOU SET US UP @I LIED TALK TO THE HAND f1 HEY CHRISTMAS TREE f2 YOU SET US UP @NO PROBLEMO HEY CHRISTMAS TREE f3 YOU SET US UP @I LIED STICK AROUND @NO PROBLEMO GET TO THE CHOPPER f3 HERE IS MY INVITATION f1 GET UP f2 ENOUGH TALK TALK TO THE HAND f3 GET TO THE CHOPPER f1 HERE IS MY INVITATION f2 ENOUGH TALK GET TO THE CHOPPER f2 HERE IS MY INVITATION f3 ENOUGH TALK CHILL YOU HAVE BEEN TERMINATED |
Bit-Twiddling Hacks
Sean Eron Anderson has collected a great bunch of bit-twiddling hacks at his website. Even if you may never have a need for operating at this level, it's a good mental exercise to to solve these kinds of puzzles.
For example, a C macro to swap two values without use of a third variable and by only using addition and subtraction:
1 2 | #define SWAP(a, b) ((&(a) == &(b)) || \ (((a) -= (b)), ((b) += (a)), ((a) = (b) - (a)))) |
If you really want to jump head-first into the deep end, check out the book Hacker's Delight by Henry S. Warren.
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