pages tagged note

Warning about low disck space

Sun, 25 Oct 2020 00:50:16 +0000

For whatever reason, even if my Macbook Pro computer booted with more than 10 GB disk space available, after working on it and having it powered on constantly for a day or two, its disk space very often will fall dramatically and sometimes even almost fill up with nominally something like 200 MB left. And it often causes issues:

Having to "manually" kill applications that are no longer responsive using Activity Monitor.
Some applications not properly exiting and saving status and metadata. For example, Eclipse workspace data, backup files in Emacs, and currently opened tabs in Google Chrome.

I made a Bash script to check and warn about low disk space and have it run periodically as a cron job.

Examples of using wget

Sun, 03 May 2020 05:47:34 +0000

Download web pages recursively under an URL¹

 wget \
 --recursive \
 --no-clobber \
 --page-requisites \
 --html-extension \
 --convert-links \
 --restrict-file-names=windows \
 --domains example.com \
 -nH --cut-dirs=some_subdir \
 -e robots=off \
 --random-wait \
 --wait 5 \
 --no-parent \
     www.example.com/subdirectory/

Substitute example.com and www.example.com/subdirectory/ with relevant expressions in your problem.
--recursive: download the entire Web site.
--domains website.org: don't follow links outside website.org.
--no-parent: don't follow links outside the directory subdirectory.
--page-requisites: get all the elements that compose the page (images, CSS and so on).
--html-extension: save files with the .html extension.
--convert-links: convert links so that they work locally, off-line.
--restrict-file-names=windows: modify filenames so that they will work in Windows as well.
--no-clobber: don't overwrite any existing files (used in case the download is interrupted and resumed).
-e robots=off: force crawling regardless of robots.txt setting.
-nH --cut-dirs=some_subdir: cuts out hostname and subdirectory name.
--random-wait: randomizes the time between requests to vary between 0.5 and 1.5 times of the waiting time specified by the --wait option.
--wait 5: number of seconds to wait between requests. (See --random-wait.)

References

linuxjournal.com. Downloading an Entire Web Site with wget. 2008. https://www.linuxjournal.com/content/downloading-entire-web-site-wget ↩

git pull from master

Thu, 09 Apr 2020 05:00:48 +0000

Check out your development branch

git checkout my_branch

Update your development branch my pulling commits from origin/master

2a. method 1

git pull origin master

ab. method 2 ``` git fetch origin master git merge FETCH_HEAD

Resolving conflcits.

git status

If it shows some files contain conflicts, manually edit the files and resolve the conflict blocks.

git add the files edited. git add my_file_1 ...

git commit git push

(END)

一些劣质网络文章惯用的标题

Fri, 03 Apr 2020 20:58:33 +0000

一些劣质网络文章，惯用模式化的哗众取宠的标题，内容往往格调低劣、似是而非、甚至错误百出，一遍一遍地收到这类「信息污染」的骚扰，不厌其烦。个人建议遇到此类，跟本就不必打开，直接跳过。

就在刚刚…
央视曝光…
震惊国人…
惊天秘密…
疯狂转发…
删前速看…
千万别吃…
还敢喝吗…
癌症前兆…
赶快扔了…
太可怕了…
大事不好…
能害死你…
多活十年…
治病防癌…
毒素最多…
神奇功效…
惊悚一幕…
价值千万…
绝密隐私…
差点丧命…
看后崩溃…
身份曝光…
北京震怒…
xxxx震惊…
高层揭秘…
强硬反击…
全民炸锅…
摊大麻烦…
国人哽咽…
西方胆寒…
美国慌了…
安倍慌了…
美国沉默…
幕后黑手…
北京发飙…
世界哗然…
果断出手…
突然翻脸…
西方崩溃…
美国崩溃…
最后警告…
噩梦来临…
世界沸腾…
国人不忍了…
中国出手了…

Examples of using Evernote

Wed, 11 Mar 2020 18:41:54 +0000

Resync all data

Open Evernote.app on macOS.
Press Shift-Option/Alt and click the synchronization wheel icon next to the search input field (as of Evernote macOS version 7.14 and 2020-3).

Refresh database indices

Press Option/Alt and click menu item 'Option > Troubleshooting'
Click 'Recreate Full Text Search Index' and 'Recreate Spotlight Search Index'.

Installing and configuring mutt

Tue, 04 Feb 2020 19:44:45 +0000

Intro to Mutt

mutt is a text-based mail client for Unix operating systems.

Installing `mutt`

brew install mutt

Installing `getmail`

brew install getmail

Examples of using afinfo

Thu, 27 Dec 2018 19:29:57 +0000

Get metadata of an audio or video file:

$ afinfo 'some_multimedia_file.m4a''

Get the duration in the unit of seconds:

$ afinfo 'some_multimedia_file.m4a' | awk '/estimated duration/ { print $3 }'

References

https://stackoverflow.com/questions/8933053/check-duration-of-audio-files-on-the-command-line

Haskell

Sat, 13 Oct 2018 03:56:52 +0000

Journal

Entering multi-line code in GHCi

Use :{ and :} to sandwich a block of code consisting of multiple lines:

Prelude> :{
Prelude| incrementInteger :: Int -> Int
Prelude| incrementInteger x = x + 1
Prelude| :}
Prelude> incrementInteger 1
2

Using the latest released version of GHC with stack

Specify the version of LTS (i.e. Long Term Support) Haskell to use by default in `$HOME/.stack/global-project/stack.yaml:

resolver: lts-8.15

As of May, 2017, the newest released version of LTS Haskell is 8.15. This version number can be found on https://www.haskell.org/downloads.

`data`, `type`, and `newtype`

https://stackoverflow.com/a/33316715

In GHCi, print the type of a symbol

  Prelude> :type Nothing
  Nothing :: Maybe a
  Prelude> :type (+)
  (+) :: Num a => a -> a -> a
  Prelude> :type print "Hello World"
  print "Hello World" :: IO ()

`Nothing` and `Maybe`

Partial application

Functions are not partial, but rather a function can be applied partially.

Function type decalaration

myFunc :: type1 -> type2 -> type3 -> type4

Pure as in 'pure functional programming languages'

Get information about a Haskell word in GHCi

Prelude> :info pure
class Functor f => Applicative (f :: * -> *) where
  pure :: a -> f a
  ...
    -- Defined in ‘GHC.Base’

Concatenating multiple strings into one using `intercalate`, `intersperse` and `concat`, and `unword`.

Function application takes precedence over any binary operator.

For example,

ourPicture = colored green (solidCircle 1) & solidCircle 2

is equivalent to

ourPicture = (colored green (solidCircle 1)) & (solidCircle 2)

guard

Changing a prefixing function to an infix binary operator

Prelude> mod 3 2
1
Prelude> 3 `mod` 2
1

Largest integer

Prelude> :{
Prelude| myInt :: Int
Prelude| myInt = 2^63 - 1
Prelude| :}
Prelude> myInt
9223372036854775807
Prelude> myInt + 1
-9223372036854775808

Prelude> :{
Prelude| minInt :: Int
Prelude| minInt = - 2^63
Prelude| :}
Prelude> minInt
-9223372036854775808
Prelude> minInt - 1
9223372036854775807

Arithmetic expression with different types of numbers

Prelude> :{
Prelude| d :: Double
Prelude| i :: Int
Prelude| d = 1.2
Prelude| i = 1
Prelude| :}
Prelude> d+i

<interactive>:48:3: error:
    • Couldn't match expected type ‘Double’ with actual type ‘Int’
    • In the second argument of ‘(+)’, namely ‘i’
      In the expression: d + i
      In an equation for ‘it’: it = d + i
Prelude> d + fromIntegral i
2.2
Prelude>

References

https://www.stackage.org
- Lookup basic information about a word, e.g. pure: https://www.stackage.org/lts-8.15/hoogle?q=pure

Haskell

Sat, 13 Oct 2018 03:56:52 +0000

Misc

http://tryhaskell.org

Softwares

IDE's

http://code.world/haskell, an online IDE to write and run Haskell code, e.g. https://code.world/haskell#Ptxn0dmOwm9z1xqIGrwPfzQ.

Installing and configuring Homebrew

Sun, 02 Jul 2017 02:09:51 +0000

Topics

How to upgrade if Homebrew stuck at an old version?

$ "$(brew --repo)" && git fetch && git reset --hard origin/master && brew update

pages tagged note

Warning about low disck space

Examples of using wget

Download web pages recursively under an URL1

References

git pull from master

一些劣质网络文章惯用的标题

Examples of using Evernote

Resync all data

Refresh database indices

Installing and configuring mutt

Intro to Mutt

Installing mutt

Installing getmail

Examples of using afinfo

References

Haskell

Journal

Entering multi-line code in GHCi

Using the latest released version of GHC with stack

data, type, and newtype

Nothing and Maybe

Partial application

Function type decalaration

Pure as in 'pure functional programming languages'

Get information about a Haskell word in GHCi

Concatenating multiple strings into one using intercalate, intersperse and concat, and unword.

Function application takes precedence over any binary operator.

guard

Changing a prefixing function to an infix binary operator

Largest integer

Arithmetic expression with different types of numbers

References

Haskell

Misc

Softwares

IDE's

Installing and configuring Homebrew

Topics

How to upgrade if Homebrew stuck at an old version?

Download web pages recursively under an URL¹

Installing `mutt`

Installing `getmail`

`data`, `type`, and `newtype`

`Nothing` and `Maybe`

Concatenating multiple strings into one using `intercalate`, `intersperse` and `concat`, and `unword`.