Chengings · July 25, 2025 16:46
diff --git a/.editorconfig b/.editorconfig
 trim_trailing_whitespace = true
diff --git a/_cheatsheets.md b/_cheatsheets.md
diff --git a/_template.md b/_template.md
diff --git a/curl_wget.sh b/curl_wget.sh
 ########
 # curl #
 ########

 curl --compressed					# Request compressed response

 curl -H "User-Agent:" https://goo.gl			# --header	Pass custom header(s) to server.
 							#		Delete an internally generated header by removing value after colon (:)

 curl -v https://captive.apple.com			# −−verbose
 							# 		’>’ means "header data" sent by curl
 							# 		’<’ means "header data" received by curl

 curl -i https://captive.apple.com			# --include	Include protocol response headers in the output

 curl -I https://captive.apple.com			# --head	Fetch headers only

 curl -s https://captive.apple.com http://neverssl.com 	# --silent	Quiet mode with multiple urls

 curl -L https://en.wikipedia.org/wiki/Special:Random	# --location	Follow redirects

 curl -w "%{url_effective}\n" -I -L -s -o /dev/null https://apple.co.uk		# print final follow url

 curl -O "https://via.placeholder.com/[50-75:5].{png,gif,jpg}"   # −−remote-name	Write output to a file named as the remOte file
 								# 		Numerical range start from 50 to 75 with an increment of 5
 								# 		And a list of png, gif and jpg
 # 50.gif 50.jpg 50.png ... 75.gif 75.jpg 75.png																															

 curl -R "https://www.iana.org/_img/bookmark_icon.ico"		# --remote-time	Set the remote file's time on the local output.

 curl -ROJ "https://www.iana.org/_img/bookmark_icon.ico"		# --remote-header-name	Use the Content-Disposition filename.
 								# 			Combined with RO options to save file with server's Last-Modified and filename.

 curl "https://via.placeholder.com/[50-75:5].png" -o "placeholder_#1.png"	# --output	Write output to <file>
 										# 		Each "glob" used in a URL gets a separate variable.
 										# 		They are referenced as '#[num]'. Start with 1
 # placeholder_50.png placeholder_55.png placeholder_60.png placeholder_65.png placeholder_70.png placeholder_75.png

 curl -o /tmp/apple.html https://captive.apple.com -o /tmp/neverssl.html http://neverssl.com	# Write multiple output files

 curl -fsSL https://deno.land/x/install/install.sh	# Multiple short options. -f  Fail silently. -S   Show error even when -s is used

 xargs curl --remote-name-all <urls.list.txt       # Download whole URLs at once and save file by its remote name. Serial manner by default.
 xargs curl -Z --remote-name-all <urls.list.txt    # --parallel	Perform transfers in parallel. Default is 50 transfers. Curl >= 7.66 (Sep 2019)
 xargs -P0 -n1 curl -O <urls.list.txt              # Alternatively, download one URL per time but use many processes (-P 0) simultaneously.

 curl -h 		# --help		Get a list of the most important and frequently used options.
 curl -h http		# HTTP and HTTPS protocol options
 curl -h verbose		# Options related to any kind of command line output of curl
 curl -h category	# Get more options listed for that specific area.
 curl -h all

 ########
 # wget #
 ########

 wget -r --no-parent					# Download whole site without parent (r)ecursively
 wget -i urls.txt						# Read URLs from a local or external f(i)le

 ##############
 # References #
 ##############

 cat <<EOF
 https://everything.curl.dev/
 https://everything.curl.dev/usingcurl/verbose/writeout
 https://curl.github.io/curl-cheat-sheet/http-sheet.html
 https://antonz.org/interactive-api-tutorials/
 https://www.gnu.org/software/wget/manual/wget.html
 EOF
diff --git a/date_time.sh b/date_time.sh
 date -u 			# Use UTC0

 date '+<format>'

 date '+%s'			# Unix Epoch time. Compatiable with BSD & GNU

 date '+%Y-%m-%d'
 # > 2199-12-31

 date '+%T'			# 24-hour clock time [00,23]; same as %H:%M:%S
 # > 22:25:59

 date '+%r'
 # > 10:25:59 pm

 date '+%c'			# Locale's date and time
 # > Thu 19 Aug 22:30:53 2021

 date '+%V'			# ISO week number of the yar [01,53]
 # > 33

 ###############
 # Adjust time #
 ###############

 ## BSD
 date -v -57M
 date -v -3H
 date -v -1d
 date -v -3d
 date -v +1d
 date -v +3m
 date -v +6m -v +15d

 ## GNU
 date -d '-57 minutes'
 date -d '-3 hours'
 date -d 'yesterday'
 date -d '-3 days'
 date -d 'tomorrow'
 date -d '+3 months'
 date -d '+6 months 15 days'

 ##################
 # Timezone & DST #
 ##################

 zdump -v GB | grep "$(date '+%Y')"		# Display GB timezone and begin/end of dst. Equivalent to https://www.gov.uk/when-do-the-clocks-change

 ##############
 # References #
 ##############

 cat <<EOF
 POSIX date: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/date.html
 GNU (coreutiles) date: https://www.gnu.org/software/coreutils/manual/html_node/date-invocation.html
 Example of GNU date: https://www.gnu.org/software/coreutils/manual/html_node/Examples-of-date.html
 EOF
diff --git a/docker.md b/docker.md
diff --git a/exiftool.md b/exiftool.md
diff --git a/eza.sh b/eza.sh
 eza -sold		# sort old files at bottom of list
 eza -snew		# sort new files at bottom of list
 eza --total-size	# show directory size

diff --git a/fd.sh b/fd.sh
 fd -0 <pattern> | xargs -0 rm -f # search and delete files, support file with space

 fd -e png -x sips -s format jpeg {} --out {.}.jpg # convert png to jpg. Required `sips`

 fd -e avi -x ffmpeg -i {} {.}.mp4 # convert avi to mp4 with default mode. Required `ffmpeg`

 # Search hidden and ignore file
 fd --hidden
 fd -H

 fd --no-ignore # disable .gitignore bahaviour
 fd -I

 fd -HI # equivalent to `fd --hidden --no-ignore`
 fd -HI '^\.' # list all hidden files and directories

 # Filtering by file modification time
 # duration uses human time: sec, min, hr, d, w, M, months, y. For instance, 2w or 1d.
 # date uses "2018-10-27 10:00:00"
 fd --changed-within <date|duration> <pattern>
 fd --changed-before <date|duration> <pattern>

 ##############
 # References #
 ##############

 cat <<EOF
 https://github.com/sharkdp/fd
 https://docs.rs/humantime/1.1.1/humantime/fn.parse_duration.html
 EOF
diff --git a/ffmpeg.md b/ffmpeg.md
diff --git a/fzf.md b/fzf.md
diff --git a/git.sh b/git.sh
 git branch -m <new name>			# Rename current branch.
 git branch -m <old> <new>			# Rename other branch.
 git branch | grep <regex> | xargs git branch -D		# --delete --force	Delete branch by regex pattern.

 git clone <repository> <directory>	# The repo is cloned into the specified directory.
 git clone <repository> .		# The repo is cloned into the current directory.

 git commit -a			# --all		Commit all local changes.
 git commit --amend		# Amend last commit message.

 # add --global after 'config' for global config
 git config user.name "username"
 git config user.email "email address"
 # Set default pull strategy to auto stash and rebase.
 git config pull.rebase true && git config rebase.autoStash true
 git config core.editor "vim"
 git config --get user.name
 git config --get user.email
 git config -l			# --list	List all variables set in config file.

 git mv <source> ... <destination>			# Move or rename a file, a directory, or a symlink.

 # use `git log` to display commit-hash.
 git revert <commit-hash>

 git restore		# Restore the file to the version in the latest commit
 git restore .		# Restore all files

 git stash
 git stash list
 git stash --include-untracked	# Include any untracked files in the stash.
 git stash apply	[<stash id>]	# Apply latest stash.
 git stash pop [<stash id>]	# Like 'apply' but also remove the stash after apply.

 git update-index --assume-unchanged <file>
 git update-index --no-assume-unchanged <file>

 git cherry-pick
 git cherry-pick -x 		# Append a line that says "(cherry picked from commit …)" to commit message.

 ##############
 # References #
 ##############

 cat <<EOF
 https://git-scm.com/docs
 https://gitexplorer.com
 EOF
diff --git a/github-cli.sh b/github-cli.sh
 # Pull request
 gh pr review --approve						# Approve the pull request of the current branch
 gh pr reivew -a
 gh pr reivew -a <number>					# Aprrove specific pull request
diff --git a/grep_ripgrep.sh b/grep_ripgrep.sh
 # Most `grep` options also AVAILABLE in `rg` too.

 cat /usr/share/dict/words
 grep -i '^.al.ation$' /usr/share/dict/words 		# Search for Incomplete Word (_AL_ATION) in the Dictionary
 grep -x '.al.ation' /usr/share/dict/words		# -x	This is equivalent to putting ^...$ around all of the search patterns (--line-regexp)

 rg --follow		# To follow symlink
 # Search hidden and ignore content
 rg --hidden
 rg -I 		# --no-filename
 rg --no-filename
 rg --no-ignore
 rg -l 		#  Only print the paths
 rg --files-with-matches
 rg -N -o 	# No line number and only matching pattern
 rg -No

 rg -u		# equivalent to --no-ignore
 rg -uu		# equivalent to --no-ignore and --hidden
 rg -v		# --invert-match

 # Search for content in specific file types
 grep "search" *.txt *.csv
 rg "search" --glob '*.txt' --glob '*.csv'
 rg "search" --type txt --type csv 
 rg --type-list # show supported file globs

 # Replacement -r, --replace
 rg -r 'additional-text-$0' # prepend text to the entire match
 rg -r '$1' # print only capturing group index 1

 # Get specific html tag
 rg -Nor '$1' 'href="(\S+)"'
 rg -Nor '$1' 'img src="(\S+)"'
 ## Get text inside <title /> and use pandoc to convert html entity to plain text
 rg -No '(?<=<title>)(.*)(?=</title>)' <(curl --silent 'url') | pandoc --from=html --to=plain

 # Context Line Control
 rg -B <num>  # --before-context   Show NUM lines before each match
 rg -A <num>  # --after-context    Show NUM lines after each match
 rg -C <num>  # --context          Show NUM lines before and after each match, equivalent to “-A <num> -B <num>”

 ##############
 # References #
 ##############

 cat <<EOF
 https://github.com/BurntSushi/ripgrep/blob/master/GUIDE.md
 EOF
diff --git a/imagemagick.md b/imagemagick.md
diff --git a/jq.sh b/jq.sh
 # Get active and owned GB servers from mullvad api.
 curl --silent --compressed https://api.mullvad.net/www/relays/all/ | jq '.[] | select(.owned == true and .active == true and .country_code == "gb") | .hostname'

 jq -r '.log.entries[].request.url' <file.json> 													# Retrieve urls from HAR file with raw output (-r) option.

 echo 'a "b" c' | jq -Rs		# Read raw input as a single long string and parse to json text. Similar to PHP's json_encode

 # Assign new value to specific key
 # For file, jq doesn't support in-place editing. Use `mktemp`, `mv` or `cp` to replace the target file.
 curl --silent https://wtfismyip.com/json | jq ".YourFuckingCountryCode = \"Unknown\""

 jq '[
  .[] |
  {
    title: .snippet.title,
    savedDate: .snippet.publishedAt,
    url: "https://youtu.be/\(.contentDetails.videoId)", 
    thumbnail: .snippet.thumbnails.high.url
  }
 ]' './Takeout/YouTube and YouTube Music/playlists/likes.json'									# Parse Youtube's like playlist
 
diff --git a/mac_os.md b/mac_os.md
diff --git a/network_utility.md b/network_utility.md
diff --git a/pihole.sh b/pihole.sh
 sqlite3 /etc/pihole/gravity.db 'SELECT * FROM domainlist' # query all domains list.

 sqlite3 /etc/pihole/gravity.db 'SELECT * FROM vw_regex_blacklist' # query specific type. This case is blacklist.regex type.

 sqlite3 /etc/pihole/gravity.db "
 UPDATE domainlist SET
  domain = 'google(tagservices|tagmanag)|tpc\.googlesyndication|app-measurement'
 WHERE id = 8
 " # update specific record

 sqlite3 -line /etc/pihole/pihole-FTL.db "
 SELECT domain, count(domain) as domain_count
 FROM queries
 WHERE status IN (2) and timestamp > "$(date -d '2 weeks ago' +%s)" and (domain NOT LIKE '%apple%' and domain NOT LIKE '%icloud%' and domain NOT LIKE '%aapl%')
 GROUP BY domain
 ORDER BY domain_count DESC
 LIMIT 20
 " # query top sites with specific timestamp and filter out Apple related domains.

 sqlite3 /etc/pihole/pihole-FTL.db "
 SELECT
  domain,
  status,
  count(domain) AS domain_count
 FROM queries
 WHERE client = ''
 GROUP BY domain
 ORDER BY domain_count DESC
 " # query domain with specific client

 SEARCH_DOMAIN='wiki'; sqlite3 -line /etc/pihole/pihole-FTL.db "
 SELECT *
 FROM (
  SELECT
    domain,
    client,
    datetime(timestamp, 'unixepoch', 'localtime') AS local_date_time
  FROM main.queries
  WHERE domain LIKE '%$SEARCH_DOMAIN%'
  ORDER BY timestamp DESC
  LIMIT 200
 )
 ORDER BY local_date_time
 " # search by domain and get output as a line with local date tiem, doamin and client.

 # query all block items with #comment
 sqlite3 -separator '' /etc/pihole/gravity.db 'select domain, "# " || comment from domainlist where type in (1, 3) and enabled = 1 order by domain'
 # query all block items with /regex/ format
 sqlite3 /etc/pihole/gravity.db 'select "/" || domain || "/" from domainlist where type in (1, 3) and enabled = 1 order by domain'
 # query all allow items with #comment
 sqlite3 -separator '' /etc/pihole/gravity.db 'select domain, "# " || comment from domainlist where type in (0, 2) and enabled = 1 order by domain'
 # query all allow items with /regex/ format
 sqlite3 /etc/pihole/gravity.db 'select "/" || domain || "/" from domainlist where type in (0, 2) and enabled = 1 order by domain'

 pihole -c -r 60 # Calculates stats and displays to an LCD and update every 60 seconds
 pihole -g # update domains 
 pihole tail # tail pihole's query log

 ## Domain list
 cat <<EOF
 https://gnuzilla.gnu.org/filters/blacklist.txt
 https://firebog.net
 EOF
diff --git a/pm2.sh b/pm2.sh
 pm2 start <file> \
  --name <app_name>
  
 pm2 restart <id|app_name|all>
 pm2 reload <id|app_name|all>
 pm2 stop <id|app_name|all>

 pm2 ls
 pm2 logs
 pm2 monit # realtime dashboard
diff --git a/raspios.sh b/raspios.sh
 sudo raspi-config

 ############
 # vcgencmd #
 ############

 vcgencmd measure_temp
 vcgencmd measure_clock arm
 vcgencmd measure_clock core     # GPU core
 vcgencmd get_config total_mem
 vcgencmd get_mem arm
 vcgencmd get_mem gpu
 # Reports whether the specified CODEC type is enabled.
 vcgencmd codec_enabled H264
 vcgencmd codec_enabled FLAC

 ##############
 # References #
 ##############

 cat <<EOF
 https://www.raspberrypi.com/documentation/computers/os.html#vcgencmd
 EOF
diff --git a/rsync.md b/rsync.md
diff --git a/sed.sh b/sed.sh
 # sed is a LINE-oriented text processing utility: it reads text, LINE by LINE, from an input stream or file.

 #################
 # SUBSTITUTION #
 #################

 # s                         Substitute command
 # /search/replacement/      Delimiter
 # ?search?replacement?      ? as a delimiter
 # _search_replacement_      _ as a delimiter
 # search                    Regular Expression Pattern Search Pattern
 # replacement               Replacement string

 sed 's/good/bad/' <<EOF
 It's a good good day.
 EOF
 # > It's a bad good day.

 ## with global (g) replacement, all matching occurrences in the line would be replaced. 
 sed 's/good/bad/g' <<EOF
 It's a good good day.
 EOF
 # > It's a bad bad day.

 sed 's/good //' <<EOF
 It's a good day.
 EOF
 # > It's a day.

 ## To replace 2 words simultaneously
 sed 's/good/new/; s/day/book/' <<EOF
 It's a good day.
 EOF
 # > It's a new book.

 # -e is POSIX standard.
 sed -e 's/good/new/' -e 's/day/book/' <<EOF
 It's a good day.
 EOF
 # > It's a new book.

 ##########
 # DELETE #
 ##########

 ## Delete comment line.
 sed '/^#/ d' <<EOF
 # this is a comment
 this is plain text.
 EOF
 # > this is plain text.

 ## Delete lines that are either blank or only contain spaces.
 sed '/^ *$/ d' <<EOF
 first line.

    
   
 final line.
 EOF
 # > first line.
 # > final line.

 # character class [:class:] must be used INSIDE bracket []
 sed '/^[[:space:]]*$/ d' <<EOF
 first line.

    
   
 final line.
 EOF
 # > first line.
 # > final line.

 ###################################
 # EDIT FILES IN-PLACE (non-POSIX) #
 ###################################

 sed -i '.backup' 's/abc/def/' thisisfile.txt

 ## GNU
 sed -i 's/abc/def/' thisisfile.txt              # overwrite file

 ## FreeBSD and macOS
 sed -i '' 's/abc/def/' thisisfile.txt           # must specific empty extension to overwrite file


 #######
 # FAQ #
 #######
 cat <<EOF
 Q: Remove comment (\#) and empty line
 A: \` sed -e 's/[[:space:]]*#.*//' -e '/^[[:space:]]*$/ d' \`				# 1st: remove from the # to the end of line. 2nd: delete blank line. Original empty line is also deleted.

 https://stackoverflow.com/a/3350246
 EOF

 cat <<EOF
 Q: Trim both ends
 A:
 sed -E 's/^[[:space:]]+|[[:blank:]]+$//g'
 # Use sub-exression \1 - \9 in replacment to replace only pritable character, no space/blank.
 sed -E -e 's/^[[:space:]]+([[:graph:]])/\1/ g' -e 's/([[:graph:]])[[:blank:]]+$/\1/ g'
 EOF

 cat <<EOF
 Q: Convert webvtt to plain txt
 A: 
 sed -E -e '/^([0-9]+:)?[0-9]{2}:[0-9]{2}.+(-->).+$/ d' -e '/^[0-9]+$/ d' -e '/^$/ d' -e '/^WEBVTT/ d' -e 's/<\/?[[:alpha:]]+>// g' -e 's/<c\.color[0-9a-fA-F]{6}>// g'
 1st expression to remove cue timing
 2nd expression to remove cue identifier
 3rd expression to remove empty line
 4th expression to remove the optional WEBVTT
 5th expression to remove tags
 6th expreesion to remove color tag
 EOF
 ##############
 # References #
 ##############

 cat <<EOF
 With various useful cases: https://www.grymoire.com/Unix/Sed.html
 https://en.wikipedia.org/wiki/Sed
 https://www.gnu.org/software/sed/manual/sed.html
 https://www.freebsd.org/cgi/man.cgi?query=sed&manpath=FreeBSD+13.0-stable
 https://pubs.opengroup.org/onlinepubs/9699919799/utilities/sed.html
 EOF
diff --git a/sqlite.sh b/sqlite.sh
 # backup db to specific path without worrying about locking mechanism (it uses transaction).
 # https://stackoverflow.com/a/41744952
 sqlite3 /etc/pihole/gravity.db '.backup /tmp/gravity.db'
 # backup and vacuum. it's sql script so file path must have quotes.
 sqlite3 /etc/pihole/gravity.db 'VACUUM INTO "/tmp/gravity.db"'
 # dump db to plain SQL file and gzip it. 
 # https://sqlite.org/cli.html#converting_an_entire_database_to_an_ascii_text_file
 sqlite3 /etc/pihole/gravity.db '.dump' | gzip -9 -c >gravity.sql.gz
 # dump specific table
 sqlite3 /etc/pihole/gravity.db '.dump adlist'
diff --git a/system_info.md b/system_info.md
diff --git a/text-processing.sh b/text-processing.sh
 head -c 20 # print the first 20 bytes of each file.
 head -n 20 # print the first 20 lines instead of the first 10.

 tail -c 20 # print the last 20 bytes.
 tail -n 20 # print the last 20 lines, instead of the last 10.
 tail -F <file> # Keep waiting for additional data to be appended and being followed (-F) has been renamed or rotated.
 tail -r # print lines in reverse order. Non-POSIX. Equivalent to `tac`

 head -n 22 | tail -n 11 # print the lines (from line number 12 to 22, both inclusive) for the input file by print the first 20 lines and then print the last 11 lines of first output.

 cut -c 1-16 # print the FIRST SIXTEEN characters of each line of the given files.
 cut -c 3- # print everything from the 3rd character to the end of each line.
 cut -c2,7 # print the 2nd and 7th character from each line of text.
 cut -c1-4 # print the FIRST FOUR characters.
 cut -c13- # print the characters from 13th position to the end.
 cut -f1-3 # Given a TAB delimited file with several columns (tsv format) print the FIRST THREE fields.
 cut -d '.' -f 1 # print 1st field by using . (dot) as a field delimiter
 rev | cut -d '.' -f 1 | rev # print last field by using . (dot) as a field delimiter

 tac <file|stdin>      # (cat) last line first

 # tr(anslate). It searchs and replaces an input.
 tr abcd wxyz # maps all characters: a => w, b => x, c => y and d => z
 tr a-d w-z
 tr A-Z a-z # Convert uppercase to lowercase
 tr '[:upper:]' '[:lower:]'
 tr -s ' ' # Squeeze repeated character to occurrence of that character. In this case, replace 'Hello        World' to 'Hello World'
 tr -s '\n' # Squeeze each sequence of repeated newlines to a single newline
 tr -d ' ' # Remove character. In this case, 'Hello  World' to 'HelloWorld'
 tr -d '[:blank:]'

 # paste is merge
 paste -s <input> # Merge input with tab delimiter. In this case, 'Line1	Line2	Line3	Line4'
 paste -s -d ';' <input> # Merge input with ';' delimiter. In this case, 'Line1;Line2;Line3,Line4'
 printf "1\n2\n3\n" | paste -sd ',' - # Merge input from standard input (stdin)  with ',' delimiter. In this case, '1,2,3'

 # Escaped string for shell
 printf '%q' "Character (computing) - Wikipedia"
 # Character\ \(computing\)\ -\ Wikipedia

 sort -u		# Unique
 sort -o <file>	# Output file. This file can be the same as one of the input files #POSIX
diff --git a/tmux.md b/tmux.md
diff --git a/uni.sh b/uni.sh
 # [e]moji [i]dentify [p]rint [s]earch
 uni e pray # name and CLDR data are searched. Handy than `search` cmd.
 #       name          (cldr)
 # 🙏	folded hands  (ask, high 5, high five, please, pray, thanks)
 # 📿	prayer beads  (clothing, necklace, religion)
 uni e -or pray cat bug

 uni i ฿£$ 
 #      cpoint  dec    utf8        html       name (cat)
 # '฿'  U+0E3F  3647   e0 b8 bf    &#xe3f;    THAI CURRENCY SYMBOL BAHT (Currency_Symbol)
 # '£'  U+00A3  163    c2 a3       &pound;    POUND SIGN (Currency_Symbol)
 # '$'  U+0024  36     24          &dollar;   DOLLAR SIGN (Currency_Symbol)

 uni p Currency_Symbol
 #      cpoint  dec    utf8        html       name (cat)
 # '$'  U+0024  36     24          &dollar;   DOLLAR SIGN (Currency_Symbol)
 # '¢'  U+00A2  162    c2 a2       &cent;     CENT SIGN (Currency_Symbol)
 # '£'  U+00A3  163    c2 a3       &pound;    POUND SIGN (Currency_Symbol)

 uni s pray        
 #      cpoint  dec    utf8        html       name (cat)
 # '📿' U+1F4FF 128255 f0 9f 93 bf &#x1f4ff;  PRAYER BEADS (Other_Symbol)
diff --git a/utilities.md b/utilities.md
diff --git a/watch.md b/watch.md
diff --git a/yt-dlp.sh b/yt-dlp.sh
 yt-dlp -a <list-of-urls-file> # inputs are separated by line break.

 yt-dlp -g <url> # get url.

 yt-dlp --skip-download --all-subs <url> # get subtitles.

 yt-dlp -x <url> # convert video files to audio-only files.

 yt-dlp -F # --list-formats List all avaialable formats.

 yt-dlp -f <number> <url> # get specific format.

 yt-dlp -f 'bestvideo[width<=3000]+bestaudio' # best video but no 4K.
	########
	# curl #
	########

	curl --compressed # Request compressed response

	curl -H "User-Agent:" https://goo.gl # --header Pass custom header(s) to server.
	# Delete an internally generated header by removing value after colon (:)

	curl -v https://captive.apple.com # −−verbose
	# ’>’ means "header data" sent by curl
	# ’<’ means "header data" received by curl

	curl -i https://captive.apple.com # --include Include protocol response headers in the output

	curl -I https://captive.apple.com # --head Fetch headers only

	curl -s https://captive.apple.com http://neverssl.com # --silent Quiet mode with multiple urls

	curl -L https://en.wikipedia.org/wiki/Special:Random # --location Follow redirects

	curl -w "%{url_effective}\n" -I -L -s -o /dev/null https://apple.co.uk # print final follow url

	curl -O "https://via.placeholder.com/[50-75:5].{png,gif,jpg}" # −−remote-name Write output to a file named as the remOte file
	# Numerical range start from 50 to 75 with an increment of 5
	# And a list of png, gif and jpg
	# 50.gif 50.jpg 50.png ... 75.gif 75.jpg 75.png

	curl -R "https://www.iana.org/_img/bookmark_icon.ico" # --remote-time Set the remote file's time on the local output.

	curl -ROJ "https://www.iana.org/_img/bookmark_icon.ico" # --remote-header-name Use the Content-Disposition filename.
	# Combined with RO options to save file with server's Last-Modified and filename.

	curl "https://via.placeholder.com/[50-75:5].png" -o "placeholder_#1.png" # --output Write output to <file>
	# Each "glob" used in a URL gets a separate variable.
	# They are referenced as '#[num]'. Start with 1
	# placeholder_50.png placeholder_55.png placeholder_60.png placeholder_65.png placeholder_70.png placeholder_75.png

	curl -o /tmp/apple.html https://captive.apple.com -o /tmp/neverssl.html http://neverssl.com # Write multiple output files

	curl -fsSL https://deno.land/x/install/install.sh # Multiple short options. -f Fail silently. -S Show error even when -s is used

	xargs curl --remote-name-all <urls.list.txt # Download whole URLs at once and save file by its remote name. Serial manner by default.
	xargs curl -Z --remote-name-all <urls.list.txt # --parallel Perform transfers in parallel. Default is 50 transfers. Curl >= 7.66 (Sep 2019)
	xargs -P0 -n1 curl -O <urls.list.txt # Alternatively, download one URL per time but use many processes (-P 0) simultaneously.

	curl -h # --help Get a list of the most important and frequently used options.
	curl -h http # HTTP and HTTPS protocol options
	curl -h verbose # Options related to any kind of command line output of curl
	curl -h category # Get more options listed for that specific area.
	curl -h all

	########
	# wget #
	########

	wget -r --no-parent # Download whole site without parent (r)ecursively
	wget -i urls.txt # Read URLs from a local or external f(i)le

	##############
	# References #
	##############

	cat <<EOF
	https://everything.curl.dev/
	https://everything.curl.dev/usingcurl/verbose/writeout
	https://curl.github.io/curl-cheat-sheet/http-sheet.html
	https://antonz.org/interactive-api-tutorials/
	https://www.gnu.org/software/wget/manual/wget.html
	EOF
	date -u # Use UTC0

	date '+<format>'

	date '+%s' # Unix Epoch time. Compatiable with BSD & GNU

	date '+%Y-%m-%d'
	# > 2199-12-31

	date '+%T' # 24-hour clock time [00,23]; same as %H:%M:%S
	# > 22:25:59

	date '+%r'
	# > 10:25:59 pm

	date '+%c' # Locale's date and time
	# > Thu 19 Aug 22:30:53 2021

	date '+%V' # ISO week number of the yar [01,53]
	# > 33

	###############
	# Adjust time #
	###############

	## BSD
	date -v -57M
	date -v -3H
	date -v -1d
	date -v -3d
	date -v +1d
	date -v +3m
	date -v +6m -v +15d

	## GNU
	date -d '-57 minutes'
	date -d '-3 hours'
	date -d 'yesterday'
	date -d '-3 days'
	date -d 'tomorrow'
	date -d '+3 months'
	date -d '+6 months 15 days'

	##################
	# Timezone & DST #
	##################

	zdump -v GB \| grep "$(date '+%Y')" # Display GB timezone and begin/end of dst. Equivalent to https://www.gov.uk/when-do-the-clocks-change

	##############
	# References #
	##############

	cat <<EOF
	POSIX date: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/date.html
	GNU (coreutiles) date: https://www.gnu.org/software/coreutils/manual/html_node/date-invocation.html
	Example of GNU date: https://www.gnu.org/software/coreutils/manual/html_node/Examples-of-date.html
	EOF
	eza -sold # sort old files at bottom of list
	eza -snew # sort new files at bottom of list
	eza --total-size # show directory size
	fd -0 <pattern> \| xargs -0 rm -f # search and delete files, support file with space

	fd -e png -x sips -s format jpeg {} --out {.}.jpg # convert png to jpg. Required `sips`

	fd -e avi -x ffmpeg -i {} {.}.mp4 # convert avi to mp4 with default mode. Required `ffmpeg`

	# Search hidden and ignore file
	fd --hidden
	fd -H

	fd --no-ignore # disable .gitignore bahaviour
	fd -I

	fd -HI # equivalent to `fd --hidden --no-ignore`
	fd -HI '^\.' # list all hidden files and directories

	# Filtering by file modification time
	# duration uses human time: sec, min, hr, d, w, M, months, y. For instance, 2w or 1d.
	# date uses "2018-10-27 10:00:00"
	fd --changed-within <date\|duration> <pattern>
	fd --changed-before <date\|duration> <pattern>

	##############
	# References #
	##############

	cat <<EOF
	https://github.com/sharkdp/fd
	https://docs.rs/humantime/1.1.1/humantime/fn.parse_duration.html
	EOF
	git branch -m <new name> # Rename current branch.
	git branch -m <old> <new> # Rename other branch.
	git branch \| grep <regex> \| xargs git branch -D # --delete --force Delete branch by regex pattern.

	git clone <repository> <directory> # The repo is cloned into the specified directory.
	git clone <repository> . # The repo is cloned into the current directory.

	git commit -a # --all Commit all local changes.
	git commit --amend # Amend last commit message.

	# add --global after 'config' for global config
	git config user.name "username"
	git config user.email "email address"
	# Set default pull strategy to auto stash and rebase.
	git config pull.rebase true && git config rebase.autoStash true
	git config core.editor "vim"
	git config --get user.name
	git config --get user.email
	git config -l # --list List all variables set in config file.

	git mv <source> ... <destination> # Move or rename a file, a directory, or a symlink.

	# use `git log` to display commit-hash.
	git revert <commit-hash>

	git restore # Restore the file to the version in the latest commit
	git restore . # Restore all files

	git stash
	git stash list
	git stash --include-untracked # Include any untracked files in the stash.
	git stash apply [<stash id>] # Apply latest stash.
	git stash pop [<stash id>] # Like 'apply' but also remove the stash after apply.

	git update-index --assume-unchanged <file>
	git update-index --no-assume-unchanged <file>

	git cherry-pick
	git cherry-pick -x # Append a line that says "(cherry picked from commit …)" to commit message.

	##############
	# References #
	##############

	cat <<EOF
	https://git-scm.com/docs
	https://gitexplorer.com
	EOF
	# Pull request
	gh pr review --approve # Approve the pull request of the current branch
	gh pr reivew -a
	gh pr reivew -a <number> # Aprrove specific pull request
	# Most `grep` options also AVAILABLE in `rg` too.

	cat /usr/share/dict/words
	grep -i '^.al.ation$' /usr/share/dict/words # Search for Incomplete Word (_AL_ATION) in the Dictionary
	grep -x '.al.ation' /usr/share/dict/words # -x This is equivalent to putting ^...$ around all of the search patterns (--line-regexp)

	rg --follow # To follow symlink
	# Search hidden and ignore content
	rg --hidden
	rg -I # --no-filename
	rg --no-filename
	rg --no-ignore
	rg -l # Only print the paths
	rg --files-with-matches
	rg -N -o # No line number and only matching pattern
	rg -No

	rg -u # equivalent to --no-ignore
	rg -uu # equivalent to --no-ignore and --hidden
	rg -v # --invert-match

	# Search for content in specific file types
	grep "search" .txt .csv
	rg "search" --glob '.txt' --glob '.csv'
	rg "search" --type txt --type csv
	rg --type-list # show supported file globs

	# Replacement -r, --replace
	rg -r 'additional-text-$0' # prepend text to the entire match
	rg -r '$1' # print only capturing group index 1

	# Get specific html tag
	rg -Nor '$1' 'href="(\S+)"'
	rg -Nor '$1' 'img src="(\S+)"'
	## Get text inside <title /> and use pandoc to convert html entity to plain text
	rg -No '(?<=<title>)(.*)(?=</title>)' <(curl --silent 'url') \| pandoc --from=html --to=plain

	# Context Line Control
	rg -B <num> # --before-context Show NUM lines before each match
	rg -A <num> # --after-context Show NUM lines after each match
	rg -C <num> # --context Show NUM lines before and after each match, equivalent to “-A <num> -B <num>”

	##############
	# References #
	##############

	cat <<EOF
	https://github.com/BurntSushi/ripgrep/blob/master/GUIDE.md
	EOF
	# Get active and owned GB servers from mullvad api.
	curl --silent --compressed https://api.mullvad.net/www/relays/all/ \| jq '.[] \| select(.owned == true and .active == true and .country_code == "gb") \| .hostname'

	jq -r '.log.entries[].request.url' <file.json> # Retrieve urls from HAR file with raw output (-r) option.

	echo 'a "b" c' \| jq -Rs # Read raw input as a single long string and parse to json text. Similar to PHP's json_encode

	# Assign new value to specific key
	# For file, jq doesn't support in-place editing. Use `mktemp`, `mv` or `cp` to replace the target file.
	curl --silent https://wtfismyip.com/json \| jq ".YourFuckingCountryCode = \"Unknown\""

	jq '[
	.[] \|
	{
	title: .snippet.title,
	savedDate: .snippet.publishedAt,
	url: "https://youtu.be/\(.contentDetails.videoId)",
	thumbnail: .snippet.thumbnails.high.url
	}
	]' './Takeout/YouTube and YouTube Music/playlists/likes.json' # Parse Youtube's like playlist
	sqlite3 /etc/pihole/gravity.db 'SELECT * FROM domainlist' # query all domains list.

	sqlite3 /etc/pihole/gravity.db 'SELECT * FROM vw_regex_blacklist' # query specific type. This case is blacklist.regex type.

	sqlite3 /etc/pihole/gravity.db "
	UPDATE domainlist SET
	domain = 'google(tagservices\|tagmanag)\|tpc\.googlesyndication\|app-measurement'
	WHERE id = 8
	" # update specific record

	sqlite3 -line /etc/pihole/pihole-FTL.db "
	SELECT domain, count(domain) as domain_count
	FROM queries
	WHERE status IN (2) and timestamp > "$(date -d '2 weeks ago' +%s)" and (domain NOT LIKE '%apple%' and domain NOT LIKE '%icloud%' and domain NOT LIKE '%aapl%')
	GROUP BY domain
	ORDER BY domain_count DESC
	LIMIT 20
	" # query top sites with specific timestamp and filter out Apple related domains.

	sqlite3 /etc/pihole/pihole-FTL.db "
	SELECT
	domain,
	status,
	count(domain) AS domain_count
	FROM queries
	WHERE client = ''
	GROUP BY domain
	ORDER BY domain_count DESC
	" # query domain with specific client

	SEARCH_DOMAIN='wiki'; sqlite3 -line /etc/pihole/pihole-FTL.db "
	SELECT *
	FROM (
	SELECT
	domain,
	client,
	datetime(timestamp, 'unixepoch', 'localtime') AS local_date_time
	FROM main.queries
	WHERE domain LIKE '%$SEARCH_DOMAIN%'
	ORDER BY timestamp DESC
	LIMIT 200
	)
	ORDER BY local_date_time
	" # search by domain and get output as a line with local date tiem, doamin and client.

	# query all block items with #comment
	sqlite3 -separator '' /etc/pihole/gravity.db 'select domain, "# " \|\| comment from domainlist where type in (1, 3) and enabled = 1 order by domain'
	# query all block items with /regex/ format
	sqlite3 /etc/pihole/gravity.db 'select "/" \|\| domain \|\| "/" from domainlist where type in (1, 3) and enabled = 1 order by domain'
	# query all allow items with #comment
	sqlite3 -separator '' /etc/pihole/gravity.db 'select domain, "# " \|\| comment from domainlist where type in (0, 2) and enabled = 1 order by domain'
	# query all allow items with /regex/ format
	sqlite3 /etc/pihole/gravity.db 'select "/" \|\| domain \|\| "/" from domainlist where type in (0, 2) and enabled = 1 order by domain'

	pihole -c -r 60 # Calculates stats and displays to an LCD and update every 60 seconds
	pihole -g # update domains
	pihole tail # tail pihole's query log

	## Domain list
	cat <<EOF
	https://gnuzilla.gnu.org/filters/blacklist.txt
	https://firebog.net
	EOF
	pm2 start <file> \
	--name <app_name>

	pm2 restart <id\|app_name\|all>
	pm2 reload <id\|app_name\|all>
	pm2 stop <id\|app_name\|all>

	pm2 ls
	pm2 logs
	pm2 monit # realtime dashboard