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misc.md

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Alghorytms and data structures to grokk

  • Bloom filter
  • Fourier transform
  • Hyperlog
  • Huffman trees
  • Count–min sketch
  • Boyer-Moore search
  • Reservoir sampling
  • Linear programming и Simplex algorithm
  • Diffie-Hellman

terminal control keys

move around:

ctrl+a ctrl+e
alt+b alt+f

delete: word: ctrl+w ctrl+d
line back and forth: ctrl+u ctrl+k

git log --all --grep='<pattern>' | ack '^commit\s+'

curl

with headers:
curl -i https://example.com
follow redirect:
curl -I -L https://example.com/redirected
post file:
curl -d @file https://example.com receiver -o saved
ls -l | curl -d @- https://example.com/receiver -o saved
verbose:
curl -v https://example.com -o /dev/null
resolve sert locally:
curl https://example.com/ --resolve example.com:443:172.0.0.1
http version:
curl --http1.0 https://example.com
curl --http2 https://example.com
save and use cookies:
curl -c cookiejar.txt https://example.com
curl -b cookiejar.txt https://example.com

curl -u 73ea6362d09a90a6db650f3e9aedf6ae90626a7e5630f2eb49d582ba: -H "Content-Type: application/json" -X POST -d '{"format": "csv", "type": "leads", "send_done_email": false }' https://close.io/api/v1/export/lead/
curl -XPOST -H "Content-Type: application/json" -d '{"contact":{"Email":"hi.bye@some.thing"}}' https://api2.autopilothq.com/v1/contac
curl -v -H 'Content-Type: application/json' -- 'https://example.com/?asdf=asdf' | jq '.results[] | {id: .id, title: .title}'

telnet -4 www.redhat.com 80
netcat: nc -w3 -4 -v www.redhat.com 80

netstat -s | grep 'Tcp:' -A 10 # outbound
netstat -ntp | grep SERVICE_PORT # inbound

free -m

dmesg -l err

ss -an | awk '{print $2}' | sort | uniq -c | sort -rn

nload

traceroute www.google.com

socat -d -d - TCP4:www.example.com:80
socat -d -d - TCP:www.example.com:80,retry=5
socat -d -d - TCP4-LISTEN:www.example.com:80,fork
socat -u STDIN STDOUT
socat -d -d READLINE\!\!OPEN:file.txt,creat,trunc SYSTEM:'read stdin; echo $stdin'

nmap google.com

openssl enc -aes-256-cbc -pbkdf2 -in un_encrypted.data -out encrypted.data
openssl enc -d -aes-256-cbc -pbkdf2 -in encrypted.data -out un_encrypted.data

docker rm -f $(docker ps -aq)
docker rmi -f $(docker images -q)
docker system prune

sudo chown -R $USER:$GROUP ~/some-file

gpg --list-keys
gpg -e -u "Sender User Name" -r "Receiver User Name" somefile
gpg -d mydata.tar.gpg

grep -R "regex" some/folder
grep -R "RequestStore" ./*/**/spec
grep "t\.string.*index:\strue" apps/api/db/migrate/*
zgrep "sign_up" beeline_kz_production_rosing_api_2020_01_05.log.gz

to see kernel version
uname -a

go fmt ./... gofmt -w ./

du -hs .
du -hs /* | sort -rh | head
du -hsx * | sort -rh | head -10
ncdu . — beautiful du alternative

hexdump -C /dev/urandom

:%!xxd # hex edit vim

pngquant **.png --ext .png --force

LC_CTYPE="C.UTF-8"

port forwarding
ssh -R 2001:localhost:143 remote.host.net
ssh -L 2001:remote.net:143 remote.net
ssh -L <local_host>:<local_port>:<remote_host>:<remove_port> <via>
ssh -L localhost:3001:example.com:4001 root@160.25.100.100
ssh -D 3000 <remote_host>

find . -name "*.ext"

rename
find . -name "*.ua.yml" -exec rename -v 's/\.ua\.yml$/\.uk\.yml/i' {} \;
find . -name '*.txt' -print0 | xargs -0 sed -i "" "s/oldword/newword/g"
find dir -name '*.rb' -type f -exec sed -i -e 's/regex/replacement/g' -- {} +
find . -type d -name src
find . -type f -name src
find . -type l -name src
find . -type d -name '*.md' -not -path 'node_modules/*'
Search files bigger than 100KB but smaller than 1MB:
find . -type f -size +100k -size -1M
Search files edited more than 3 days ago:
find . -type f -mtime +3
Search files edited in the last 24 hours:
find . -type f -mtime -1
You can delete all the files matching a search by adding the -delete option. This deletes all the files edited in the last 24 hours:
find . -type f -mtime -1 -delete
You can execute a command on each result of the search. In this example we run cat to print the file content:
find . -type f -exec cat {} ;

tar -zcvf archive.tar.gz directory/

Trace DNS lookup
dig @8.8.8.8 +trace github.com

Constant O(1)
Logarithmic O(log N)
Linear O(N)
Linearithmic O(N log N)
Polynomial O(N ^ 2)
Exponential O(2 ^ N)
Factorial O(N!)

SQL a quick HTML report of your databases
psql -c "\l+" -H -q postgres > out.html

See how much space your tables (and indexes!) are taking up space
SELECT
relname AS table_name,
pg_size_pretty(pg_total_relation_size(relid)) AS total,
pg_size_pretty(pg_relation_size(relid)) AS internal,
pg_size_pretty(pg_table_size(relid) - pg_relation_size(relid)) AS external,
pg_size_pretty(pg_indexes_size(relid)) AS indexes
FROM pg_catalog.pg_statio_user_tables ORDER BY pg_total_relation_size(relid) DESC;