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https://github.com/dongyx/hardv

A Powerful Flashcard Program for Linux, macOS, and Other Unix-like Systems
https://github.com/dongyx/hardv

cli command-line flashcard flashcard-application flashcard-generator flashcards line-oriented linux plaintext quiz shell terminal unix unix-filter unix-philosophy

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A Powerful Flashcard Program for Linux, macOS, and Other Unix-like Systems

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README 

        
HardV

=====



HardV is a powerful flashcard program for Linux, macOS and other Unix-like systems.

The key features are listed below.



- Almost everything can be customized,

with any programming language you prefer.

E.g.:



	- HardV runs in the CLI mode by default;

	but you may configure it to a TUI program,

	or to view images in a GUI window.



	- HardV can open the editor;

	send the content you wrote

	to an online judging system,

	and determine the next quiz time by the judging result.



	- It can be used to implement

	keyboard shortcut practice,

	cloze deletion,

	text-to-speech review,

	typing in the answer,

	and more.



- The format of input files are

easy to be parsed by both human and other Unix utilities

like `grep`, `sed`, and `awk`.



- Metadata like scheduled time is written back to input files;

thus all your data is in files created and managed by yourself.



- HardV respects contents of input files as long as possible;

you could use empty lines to layout your card files.



- HardV is a Unix filter in the default mode;

that makes it easy to be called by other programs.

Eg. You could pipe HardV to a voice synthesizer to make an audio quiz.



**Table of Contents**



* [Getting Started](#getting-started)

* [Customize Quizzes](#customize-quizzes)

* [Installation](#installation)

* [Input Format](#input-format)

* [Documentation](#documentation)

* [Credits](#credits)



Getting Started

---------------



First of all, let's see the standard quiz of HardV.



Suppose we have a file `input.fc` consists of flashcards.



	$ cat input.fc



	Q	hex(128) = ?

	A	0x80

	%%

	Q	hex(32768) = ?

	A	0x8000

	%%

	Q	the most famous C program from K&R, second edition

	A	#include 

		

		main()

		{

			printf("hello world\\n");

		}



Cards are separated by `%%` on a line by itself.

The key and value of a field in a card are separated by a tab character.

Subsequent lines in the value are indented by a tab character.

(See the [*Input Format*](#input-format) section)



We could use HardV to run a quiz.

	

	$ hardv input.fc

	...



	Q:



		hex(128) = ?



	Press  to check the answer.



	A:



		0x80



	Do you recall? (y/n/s)

	y



	...



After running a quiz,

two new fields `PREV` and `NEXT` may be inserted to the original file,

to indicate the previous and the next scheduled quiz time.



	NEXT    2001-08-21 15:31:06 -0500

	PREV    2001-08-23 15:31:06 -0500

	Q       hex(128) = ?

	A       0x80



You could manually modify these two fields to tune the quiz time.



The time interval is doubled if you are able to recall the card.

Otherwise the card will be scheduled at 24 hours later.

See the man page `hardv(1)` for detail.



To customize the quiz,

a `MOD` field is required to be added to the card.

See the [*Customize Quizzes*](#customize-quizzes) section.



Customize Quizzes

-----------------



If a card contains the `MOD` field,

the customized quiz is used.

The value of the `MOD` field is passed to `/bin/sh -c` by HardV,

and several environment variables are set,

for the mod can read information about the card.

The exit status of the mod determines the action HardV would take

for the card.



Let's write a simple mod called `recite`.

When a card with this mod is quizzed,

it prints the content of the `Q` field,

then the user is required to copy the `A` field exactly.

If the answer is correctly copied,

this mod notifies HardV that the user is able to recall the card.

If the answer is incorrectly copied,

this mod notifies HardV that the user is unable to recall the card.

The user can type `!` to skip the card,

and this mod notifies HardV to update nothing.



We create a shell script named `/usr/loca/bin/recite`

with the following content and make it executable.



	#!/bin/sh



	# Print a blank line before quizzing a card, except the first

	if ! [ "$HARDV_FIRST" ]; then

		printf '\n'

	fi

	printf 'Q: %s\n' "$HARDV_Q"	# Print the question

	printf '(recite) A: '		# Print the prompt

	read a				# Read the user-input line to variable a

	if [ "$a" = "!" ]; then

		exit 2;			# Skip this card

	fi

	if [ "$a" = "$HARDV_A" ]; then

		echo 'Correct!'

		exit 0;			# The user is able to recall

	fi

	printf 'Wrong! The answer is: %s\n' "$HARDV_A"

	exit 1;				# The user is unable to recall



For the card we want to enable this mod,

we add the `MOD` field with the value `recite`.

(Ensure `/usr/local/bin` is in the `$PATH` environment variable)



	$ cat input.fc



	MOD	recite

	Q	hex(128) = ?

	A	0x80

	%%

	MOD	recite

	Q	hex(32768) = ?

	A	0x8000



When we run `hardv` on this card, `recite` is called.



	$ hardv input.fc

	Q: hex(128) = ?

	(recite) A: 0x80

	Correct!



	Q: hex(32768) = ?

	(recite) A: 0x800

	Wrong! The answer is: 0x8000



Mods can also be embedded in the input file,

demonstrated by the following.



	$ cat input.fc



	MOD

		! [ "$HARDV_FIRST" ] && printf '\n'

		printf 'Q: %s\n(recite) A: ' "$HARDV_Q"

		read a

		[ "$a" = "!" ] && exit 2;

		if [ "$a" = "$HARDV_A" ]; then

			echo 'Correct!'

			exit 0;

		fi

		printf 'Wrong! The answer is: %s\n' "$HARDV_A"

		exit 1;

	Q	hex(128) = ?

	A	0x80



This could be very handy if you want to wrap existed programs to a

HardV mod.



See the man page `hardv(1)` for detail about how to implement a mod.



Installation

------------



- Choose a version from

the [release page](https://github.com/dongyx/hardv/releases);

The latest is always recommended unless otherwise noted in the

release note.



- Extract the source.



- Execute in the source tree:



	~~~

	$ make

	$ sudo make install

	~~~



`make install` copies files to `/usr/local` by default.

The man page `hardv(1)` is shipped with the installation.



Input Format

------------



A card is a key-value structure contains at least two fields `Q`

and `A`.



The key and the value are separated by a tab character or a newline

character.

Every line in the value which is not on the same line with the key

must start with a tab character, except for blank lines.

For blank lines in the value, the leading tab character is optional.



Cards are typically separated by `%%` on a line by itself.

In fact, any line starting with `%` is regarded as a card separator.



Empty cards are ignored.

In the standard quiz, the leading and trailing empty lines in values are ignored too.

Thus separators can be used as comments,

and you could add empty lines for readability,

demonstrated by the following.



	%% This is a card set for hardv(1)

	%% Created at Feb 1, 1997



	Q       hex(256) = ?

	A

		0x100



	%%



	Q       hex(128) = ?



	A	0x80



	%% Arithmetic cards begin



	Q       1 + 1 = ?

	A       2

	%%

	Q       8 - 5 = ?

	A       3



	%% Arithmetic cards end



See the man page `hardv(1)`

for the full description of the input format.



Documentation

-------------



Calling `hardv --help` prints a brief help.

Full description is documented in the man page `hardv(1)`.



Credits

-------



HardV was created by [DONG Yuxuan](https://www.dyx.name) in 2022.



Other code contributors are listed below:



- Song, Yuanjia