We started producing shows as Today with a Techie on 2005-09-19, 19 years, 0 months, 26 days ago. Our shows are produced by listeners like you and can be on any topics that "are of interest to hackers". If you listen to HPR then please consider contributing one show a year. If you record your show now it could be released in 1 days.
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Hosted by Dave Morriss on 2024-10-15 is flagged as Explicit and released under a CC-BY-SA license.
JSON, JavaScript Object Notation, jq, jq filter, jq language.
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Duration: 00:25:53
In this episode we will continue looking at basic filters. Then we
will start looking at the feature that makes jq very
powerful, the ability to transform JSON from one form to another. In
essence we can read and parse JSON and then construct an alternative
form.
.[<number>:<number>]This filter allows parts of JSON arrays or strings to be extracted.
The first number is the index of the elements of the array or string, starting from zero. The second number is an ending index, but it means "up to but not including". If the first index is omitted it refers to the start of the string or array. If the second index is blank it refers to the end of the string or array.
This example shows using an array and extracting part of it:
$ x="[$(seq -s, 1 10)]"
$ echo "$x"
[1,2,3,4,5,6,7,8,9,10]
$ echo "$x" | jq -c '.[3:6]'
[4,5,6]Here we use the seq command to generate the numbers 1-10
separated by commas in a JSON array. Feeding this to jq on
its standard input with the slice request '.[3:6]' results
in a sub-array from element 3 (containing value 4), up to but not
including element 6 (containing 7). Note that using the
'-c' option generates compact output, as we discussed in
the last episode.
For a string, the idea is similar, as in:
$ echo '"Hacker Public Radio"' | jq '.[7:10]'
"Pub"Notice that we provide the JSON string quotes inside single quotes
following echo. The filter '.[7:10]' starts
from element 7 (letter "P") up to but not including element 10
(letter "l").
Both of the numbers may be negative, meaning that they are offsets from the end of the array or string.
So, using '.[-7:-4]' in the array example gives the same
result as '.[3:6]', as do '.[3:-4]' and
'.[-7:6]'. This example uses the x variable
created earlier:
$ for f in '.[-7:-4]' '.[3:6]' '.[3:-4]' '.[-7:6]'; do
> echo "$x" | jq -c "$f"
> done
[4,5,6]
[4,5,6]
[4,5,6]
[4,5,6]Similarly, using '.[-12:-9]' gives the same result as
'.[7:10]' when used with the string.
$ echo '"Hacker Public Radio"' | jq '.[-12:-9]'
"Pub"As a point of interest, I wrote a little Bash loop to show the positive and negative offsets of the characters in the test string - just to help me visualise them. See the footnote1 for details.
Finally, here is how to get the last character of the example string using positive and negative offsets:
$ echo '"Hacker Public Radio"' | jq '.[18:]'
"o"
$ echo '"Hacker Public Radio"' | jq '.[-1:]'
"o".[]This filter generates values from iterating through an array or an
object. It is similar to the .[index] syntax we have
already seen, but it returns all of the array elements:
$ arr='["Kohinoor","plastered","downloadable"]'
$ echo "$arr" | jq '.[]'
"Kohinoor"
"plastered"
"downloadable"The strings in the array are returned separately, not as an array. This is because this is an iterator, and its output can be linked to other filters.
It can also be used to iterate over values in an object:
$ obj='{"name": "Hacker Public Radio", "type": "Podcast"}'
$ echo "$obj" | jq '.[]'
"Hacker Public Radio"
"Podcast"This iterator does not work on other data types, just arrays and objects.
An alternative iterator .[]? exists which ignores
errors:
$ echo "true" | jq '.[]'
jq: error (at <stdin>:1): Cannot iterate over boolean (true)Ignoring errors:
$ echo "true" | jq '.[]?'There are two operators that can be placed between filters to combine
their effects: the comma (',') and the
pipe ('|').
The comma (',') operator allows you to chain together
multiple filters. As we already know, the jq program feeds
the input it receives on standard input or from a file into whatever
filter it is given. So far we have only seen a single filter being
used.
With the comma operator the input to jq is fed to all of
the filters separated by commas in left to right order. The result is a
concatenation of the output of all of these filters.
For example, if we take the output from the HPR stats page which was
mentioned in part 1
of this series of shows, and store it in a file called
stats.json we can view two separate parts of the JSON like
this:
$ curl -s https://hub.hackerpublicradio.org/stats.json -O
$ jq '.shows , .queue' stats.json
{
"total": 4756,
"twat": 300,
"hpr": 4456,
"duration": 7640311,
"human_duration": "0 Years, 2 months, 29 days, 10 hours, 18 minutes and 31 seconds"
}
{
"number_future_hosts": 6,
"number_future_shows": 18,
"unprocessed_comments": 0,
"submitted_shows": 0,
"shows_in_workflow": 51,
"reserve": 20
}This applies the filter .shows (an object
identifier-index filter, see part 2)
which returns the contents of the object with that name, then it applies
filter .queue which returns the relevant JSON object.
The pipe ('|') operator combines filters by feeding the
output of the first (left-most) filter of a pair into the second
(right-most) filter of a pair. This is analogous to the way the same
symbol works in the Unix shell.
For example, if we extract the 'shows' object from
stats.json, we can then extract the value of the
total' key' as follows:
$ jq '.shows | .total' stats.json
4756Interestingly, chaining two object identifier-index filters gives the same output:
$ jq '.shows.total' stats.json
4756(Note: to answer the question in the audio, the two filters shown can
also be written as '.shows .total' with intervening
spaces.)
We will see the pipe operator being used in many instances in upcoming episodes.
It is possible to use parentheses in filter expressions in a similar way to using them in arithmetic, where they group parts together and can change the normal order of operations. They can be used in other contexts too. The example is a simple arithmetic one:
$ jq '.shows.total + 2 / 2' stats.json
4757
$ jq '(.shows.total + 2) / 2' stats.json
2379Here we are using a file called countries.json obtained
from the GitHub
project listed below. This file is around 39,000 lines long so it is
not being distributed with the show. However, it's quite interesting and
you are encouraged to grab a copy and experiment with it.
I will show ways in which the structure can be examined and reported
with jq in a later show, but for now I will show an example
of extracting data:
$ jq '.[42] | .name.common , .capital.[]' countries.json
"Switzerland"
"Bern""name",
with the common name in a keyed field called "common", thus
the filter .name.common."capital"
holding an array containing the name (or names) of the capital city (or
cities). The filter .capital.[] obtains and displays the
contents of the array.comma operator between the
filters.Another search of the countries.json file, this time
looking at the languages spoken. There is an object called
"languages" which contains abbreviated language names as
keys and full names as the values:
$ jq '.[42] | .name.common , .capital.[] , .languages' countries.json
"Switzerland"
"Bern"
{
"fra": "French",
"gsw": "Swiss German",
"ita": "Italian",
"roh": "Romansh"
}.languages we get the whole object,
however, using the iterator .[] we get just the
values.$ jq '.[42] | .name.common , .capital.[] , .languages.[]' countries.json
"Switzerland"
"Bern"
"French"
"Swiss German"
"Italian"
"Romansh"jq to generate more meaningful output.In the next episode we will look at construction - how new JSON output data can be generated from input data.
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Duration: 00:18:42
JAMBOREE.rmccurdy.com : SOCFortress CoPilot / Velociraptor / Wazuh
PREP TIME
5 minutes
TOTAL TIME
5 minutes
Ingredients
½ cup mayonnaise
½ cup sour cream
3 Tablespoons pickled jalapeno juice (from a jar of pickled jalapenos)
3 Tablespoons pickled jalapenos (diced)
2 teaspoon paprika
2 teaspoons ground cumin
1 teaspoon garlic granules
1 teaspoon onion powder
½ teaspoon salt (or to taste)
½ teaspoon chili powder
Hosted by Ken Fallon on 2024-10-11 is flagged as Clean and released under a CC-BY-SA license.
FOSDEM, HAM.
HAM radio.
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Duration: 00:52:55
Known in the Hacker world as the Ham Radio Guy at FOSDEM, Kristoff Bonne ON1ARF, and Ken Fallon PA7KEN/G5KEN sit down to discuss "vergrijzing, changing attitudes, and increasing participation in the Amateur Radio Community."
Hosted by Archer72 on 2024-10-10 is flagged as Clean and released under a CC-BY-SA license.
AutoMaintenance, AutoShop.
general.
1.
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Duration: 00:06:54
Archer72 rambles about an experience in a Wal-Mart oil change shop, and a positive interaction with a customer there.
Hosted by Some Guy On The Internet on 2024-10-09 is flagged as Clean and released under a CC-BY-SA license.
MovieReview, LinuxLUGcastz.
general.
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Duration: 00:34:27
Welcome to Episode 237 the LinuxLUGcastz
The Artifice Girl is a 2022 science fiction psychological thriller written and directed by Franklin Ritch, produced by Aaron B. Koontz and released direct to VOD. It stars Tatum Matthews, Sinda Nichols, David Girard, Lance Henriksen, and Franklin Ritch. NGO agents discover a revolutionary Artificial intelligence (AI) computer program that uses a digital child to catch online predators, it advances far more rapid than they could have imagined, posing unforeseen challenges for the relationship between humans and AI.
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
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Duration: 00:16:09
Picture 1
Shows the EPROM (Erasable Programmable Read Only Memory) fitted with a
label marked JAF7. EPROM's can be erased by removing the sticker and
exposing the device to strong ultraviolet light. I incorrectly refer to
it as a PROM (Programmable Read Only Memory. Below it is the old leaking
PLL backup battery.
Wikipedia article about EPROM’s (Erasable Programmable Read Only Memory)
Link / example of a Fluke 77 DMM (Digital Multi Meter) I mention that I used it to check the battery voltage of the original PLL backup battery which I think was manufactured around 1984. I was very surprised to find that the battery which is likely 40 years old had a battery voltage of 3.2V which is a healthy voltage. The battery still needed changed due to liquid (probably acid) which can be seen in picture 1 being present on the top surface of the battery.
Picture 2
Shows me extending the new battery terminal using the leg of a 1.8 kilo
ohm resistor. Note that the resistor leg is shiny because this time I
scraped away the surface oxidation using pliers prior to soldering it in
place. This improves the final solder joint.
Hosted by HPR Volunteers on 2024-10-07 is flagged as Explicit and released under a CC-BY-SA license.
Community News.
HPR Community News.
2.
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Duration: 01:10:21
Welcome to our new host:
hairylarry.
These are comments which have been made during the past month, either to shows released during the month or to past shows. There are 23 comments in total.
There are 6 comments on 6 previous shows:
There are 17 comments on 8 of this month's shows:
Policy decisions surrounding HPR are taken by the community as a whole. This discussion takes place on the Mail List which is open to all HPR listeners and contributors. The discussions are open and available on the HPR server under Mailman.
The threaded discussions this month can be found here:
https://lists.hackerpublicradio.com/pipermail/hpr/2024-September/thread.htmlWith the kind permission of LWN.net we are linking to The LWN.net Community Calendar.
Quoting the site:
This is the LWN.net community event calendar, where we track events of interest to people using and developing Linux and free software. Clicking on individual events will take you to the appropriate web page.
The further back in time we go with these repairs, the more challenging they tend to become because of the variations in the way shows were put together. It has been difficult to process more than five a day, and there have been a few breaks along the way!
The current state of the project is that it has been completed:
+------------+------------+--------------+------------------+
| date | repairable | repair_count | unrepaired_count |
+------------+------------+--------------+------------------+
| 2024-10-03 | 352 | 352 | 0 |
+------------+------------+--------------+------------------+
Hosted by Ahuka on 2024-10-04 is flagged as Clean and released under a CC-BY-SA license.
Science fiction, Doctor Who, William Hartnell.
Science Fiction and Fantasy.
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Duration: 00:14:37
This is a look at the very first serial of Doctor who, and how the cast was first put in place. It is in many ways an unlikely story for a show that has gone on for 60 years and counting. I find the early stories to be charming and worth a look, and many things from these early stories come back in later stories as well.
Hosted by Some Guy On The Internet on 2024-10-03 is flagged as Clean and released under a CC-BY-SA license.
headlamp, backpack.
general.
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Duration: 00:24:16
black diamond spot 400 headlamp
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
Hosted by Swift110 on 2024-10-02 is flagged as Clean and released under a CC-BY-SA license.
batteries, remote control, tv.
general.
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Duration: 00:08:37
My telegram is t.me/forthenerdsremix
irc is #forthenerds on libera
Dirt Simple Photo Gallery put me on the path to Plain Text Programs
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Sgoti talks about Good Samaritan laws. Good Heavens!
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About setting up a rack mounted home lab
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The Hallway track from Spectrum24 day 2
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The Hallway track from Spectrum24 day 1
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Part 4 deals with getting access to the PLL backup battery.
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Neuro diverse TV/Movies, DIY Liquid Conductive paint, cold hands / feet, Linux CPU info apps
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We start our dive into the mechanics of this game
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The HPR community comes together to converse
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Plain Text Programs-what they are-what they do-why they're good-and why they're not for everything
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A response to hpr1949, about the KOReader
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Sgoti talks about resources for new Linux users.
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Trollercoaster interacts with the Community News Summary of August 2024
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It's how to use the normal menu items to make online tabular data easier to use.
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Kevie discusses Dynamic DNS and how to setup DuckDNS on a Raspberry Pi
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Part 3 deals with the replacement of the clock backup battery on my TS-940S
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Some random technical items this time
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An introduction to one of my favorites, Doctor Who
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The HPR community comes together to converse
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Personal reflections on hobbies, obsessive interests and mental health
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Ken interviews Gary Williams about rebooting the OggCamp meetup
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HPR Volunteers talk about shows released and comments posted in August 2024
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Social Engineering more contributions to HPR by picking when to publish your show
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How to use the tune2fs program to reduce the reserved block percentage value
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Dave records an episode for HPR explaining why he hasn't recorded an episode for HPR.
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Replacing batteries in my HF Amateur radio TS-940S. Covers replacement of the clock battery
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A brief introduction to the rkvm software KVM
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We start our look at the next game in the Civilization franchise, Civilization IV
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The HPR community comes together to converse
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Archer72 responds to Ken's comment on HPR4172 with hopefully enough detail
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