Wait until able to connect

while ! nc -w5 -z 10.0.0.100 22; do echo "hello"; done

Log executed command

14:27 $ (set -x; sleep 1 && sleep 2)
+ sleep 1
+ sleep 2

linux: List all IP addresses in a network

To list ip addresses of all connected to the network devices, use this command:

nmap -sn 192.168.0.0/24

bash: How to check what hides behind an alias

To check what command is assigned to the alias use type command:

$ type gl
gl is aliased to `git log --oneline'

Monitor process with top

One liner to monitor a process with the name /wshub:

top -p "$(pgrep -f /wshub)"

Monitor cpu and memory usage of the process

Print every second cpu and memory usage of the process:

watch -n 1 "ps -eo pid,pcpu,pmem,args | kazy -i xnotitle -e kazy"

Get size of the subfolders

Use this command to print size of the subfolders:

du -sh *

If you want to exclude Permission denied errors, for example:

du -sh * 2>/dev/null

linux: Print exit code of the last command

To print exit code of the last command type:

echo $?

bash: How to clean logs

One of the fastest and easiest ways is just like this:

> /var/log/syslog

bash: How to remove all *.pyc files

Remove all *.pyc files from the current directory (and subdirectories):

find . -name \*.pyc -delete

bash: Colourful side-by-side command line diff

I have never liked default linux diff command. The more changes you make, the less informative it becomes. When you work with git it would be nice to have side-by-side comparison of original file and a new file with changes. Graphical tools like smartgit and meld do it really impressive.

But sometimes it is more comfortable to use command line tools. For colourful side-by-side git diff you can use cdiff. The simpliest way to install it is with pip package manager:

pip install cdiff

Then in your repository run:

cdiff -s

And the result is gorgeous!

The next tool is called icdiff. It does basicly the same, but with files. Install it with that command:

curl -s https://raw.githubusercontent.com/jeffkaufman/icdiff/release-1.2.0/icdiff \
  | sudo tee /usr/local/bin/icdiff > /dev/null \
  && sudo chmod ugo+rx /usr/local/bin/icdiff

Use it like this:

icdiff file1 file2

bash: Как изменить командную строку в bash

В bash командную строку можно изменить присвоив значение PS1 в терминале. Вот эта команда добавит время, полный путь в запрос, а также выведет его на следующую строку:

$ PS1="\[\033[01;32m\]\t \[\033[01;34m\]\w\[\033[00m\]\[\033[1;32m\]\n\$ \[\033[m\]"

Чтобы изменения сохранились после перезагрузки, добавьте эту строку в файл ~/.bashrc:

# Configure prompt
export PS1="\[\033[01;31m\]\$([ \$? == 0 ] || echo \"!\$? \" )\[\033[00m\]\[\033[01;32m\]\t \[\033[01;34m\]\w\[\033[00m\]\[\033[1;32m\]\n\$ \[\033[m\]"

Список специальных символов:

\d The date, in "Weekday Month Date" format (e.g., "Tue May 26").

\h The hostname, up to the first . (e.g. deckard)

\H The hostname. (e.g. deckard.SS64.com)

\j The number of jobs currently managed by the shell.

\l The basename of the shell's terminal device name.

\s The name of the shell, the basename of $0 (the portion following the final slash).

\t The time, in 24-hour HH:MM:SS format.

\T The time, in 12-hour HH:MM:SS format.

\@ The time, in 12-hour am/pm format.

\u The username of the current user.

\v The version of Bash (e.g., 2.00)

\V The release of Bash, version + patchlevel (e.g., 2.00.0)

\w The current working directory.

\W The basename of $PWD.

\! The history number of this command.

\# The command number of this command.

\$ If you are not root, inserts a "$"; if you are root, you get a "#" (root uid = 0)

\nnn The character whose ASCII code is the octal value nnn.

\n A newline.

\r A carriage return.

\e An escape character.

\a A bell character.

\\ A backslash.

\[ Begin a sequence of non-printing characters. (like color escape sequences). This allows bash to calculate word wrapping correctly.

\] End a sequence of non-printing characters.

bash: Как следить за процессами

Для того, чтобы вывести в консоль информацию о каком либо процессе (фильтруется по имени) можно воспользоваться командой:

watch -n 1 'ps ax -o rss,user,command | sort -nr | grep celery |head -n 5'

Эта команда выведет все процессы связанные с celery и ограничит вывод 5 штуками

bash: Как выводить в консоль изменения в файле

Эта команда позволяет выводить в консоль последние строчки в файле. Если в файл будут добавлены новые строки, они автоматически отобразятся в консоли. Очень удобно следить за логами:

tail -f filename

где filename - имя файла