Useful Commands

Using Ubuntu 14.04.3 LTS

Run 100 http requests with a concurrency of 10 using apache bench

ab -n 100 -c 10 http://localhost:9999/someAPICall

Import all of the json files in the current directory into a mongo collection

for f in *.json; do echo "Processing $f file.." && mongoimport -d mydb -c mycoll $f; done

Export a limited amount of documents from a collection to a json file

mongoexport -h host_name -d db_name -c coll_name --limit 10 --out export.json

Show numeric version of file permission

stat -c "%a %n" /path/to/file

Bump process priority (-20 to 20 negatives require root) -20 highest, 20 lowest

nice -10 command

View a list of all locally installed packages

dpkg --get-selections | grep -v deinstall

View recently installed packages

awk '$3~/^install$/ {print $4;}' /var/log/dpkg.log

Print directory size (human readable)

du -sh *

List all users

cut -d: -f1 /etc/passwd

Print the amount of items in the current directory every 2 seconds

while sleep 2; do ls | wc -l; done

Capture a local backup of a collection on a remote mongo database and store in a zip file

mongodump --host server.url --db db_name --collection coll_name --out - | zip collection_dump.zip

Checkout git branch and update working directory

git checkout branch_name

Show all local and remote git branches

git branch -av

Delete a remote git branch

git push origin --delete BRANCH

Set git credentials

git config --global user.name "User"

git config --global user.email "foo@bar.com"

Display git settings

git config --list

Display a menu showing alternative JRE installations

sudo update-alternatives --config java

Restart apache

/etc/init.d/apache2 restart

Insert a new line above every line that matches your phrase and save the output

sed '/phrase/{x;p;x;}' input.txt > output.txt

Echo out the line count and length of longest line in a file

```echo "Line count:" wc -l < FILENAME && echo "Longest line length: " `wc -L < FILENAME````

Display a snapshot of the process using the most memory

ps aux --sort -rss | head -n 2

Display a snapshot of the process with heaviest CPU usage

ps aux | sort -rk 3,3 | head -n 2

Postgres shell

psql -h myhost -d mydb -U myuser

Grep for something and display the 3 lines before and after your match

grep -A 3 -B 3 "something" example.log

Ping scan the specified subnet and return a list of IP's that respond

nmap 192.168.0.0/24

Identify all of the hostnames of the IP's found in a specified subnet

nmap -sL 192.168.0.0/24

Check if a port is in use

lsof -i :27017

Remove all but the 5 latest files in a directory

rm `ls -t | awk 'NR>5'

Check CRON installation log

grep CRON /var/log/syslog

Generate key pair

ssh-keygen -t rsa

Force SSH to use a private key

ssh -i /path/to/private host@host.com

SSH maximum verbosity

ssh -vvv host@host.com

Add user

sudo useradd caleb

Run apache configuration syntax test

apachectl configtest

Grab a file from a ftp server with curl

$ curl -u ftpuser:ftppass -O ftp://ftp_server/test.txt

Find all hidden files in a directory

find /tmp -type f -name ".*"

Substitute "foo" with "bar" ONLY for lines which contain "baz"

sed '/baz/s/foo/bar/g'

Find the numbers in my log file between "100% complete - " and "files moved" and add them up

cat example.log | grep -o -P '(?<=100% complete - ).*(?=files moved)' | awk '{ SUM += $1} END { print SUM }'

Set an environment variable for one command only

var=value command'

Find the unique occurences of new lines containing the text "key:" in all of the files in the current directory

grep -rh "^key:" | sort -u

SFTP using a private key for authentication

sftp -o IdentityFile=/path/to/private_key user@host

Show available aliases

alias or compgen -a

Remove all aliases

unalias -a

Remove a specific alias

unalias alias_name

Find all empty files in the home directory

find ~ -empty

Open a file in vim on a specific line

vim +14 Application.java

Open vim on the first match of the specified term

vim +/main Application.java

Ignore whitespace when comparing files

diff -w a.c b.c

Show android devices connected

adb devices

Enter device shell using android debug bridge

adb shell

Take a screencap of your device and save it to a png on your machine

adb shell screencap -p | perl -pe 's/\x0D\x0A/\x0A/g' > screen.png

Convert a pdf document to a text file

pdftotext source.pdf

Get the latest Docker package

curl -fsSL https://get.docker.com/ | sh

Add user to Docker group

sudo usermod -aG docker username

Start the Docker daemon

sudo service docker start

Create and run a Docker container using a specific image

docker run image_name

View local Docker images

docker images

Build a Docker image using the Dockerfile in the current directory

docker build -t image_name .

Tag a Docker (image id, accountname/imagename:version-label/tag)

docker tag 123abc123abc cbrowne/mydocker:latest

docker login --username=cbrowne --email=calebrjbrowne@gmail.com

Push an image to a Docker Hub repository

docker push cbrowne/mydocker

Remove Docker local image by ID or name

docker rmi -f 7d9495d03763

docker rmi -f cbrowne/mydocker

Run an interactive shell in a Docker image

docker run -i -t mydocker /bin/bash

Run an interactive shell in a Docker image and set the hostname

sudo docker run -h mydocker -i -t mydocker /bin/bash

Cat backwards

tac my.log

Start memcached on 192.168.9.110 port 11211 with 1024MB maximum cache size in the background as a daemon

memcached -d -m 1024 -p 11211 -l 192.168.0.110

cat into a protected file

cat <whatever> | sudo tee <--append> /write/protected/file

chrisbarbour/useful-commands

Useful Commands