Unix commands

unix-commands.md

Linux hints and tricks

• Create shortcut in Ubuntu-Gnome Alacarte

Memory: number of slots and maximum RAM that could be installed

sudo dmidecode -t 16 dmidecode -t memory >> show memory slots

watch free -m >> shows free memory watch -n 2 <command_to_execute> >> execute the command every 2 seconds

If you create a directory under ~/bin, everything you copy there will be in the PATH directly.

Creation of system user

addUser --system --disabled-password --shell=/bin/false jenkins

Get the MaxPermSize used in a project

jinfo -flag MaxPermSize <process_id>

jar tf *.jar >> view JAR content

Install several versions of Maven

http://dev-maziarz.blogspot.com.es/2012/09/ubuntu-1204-installing-both-maven3-and.html

Create launcher in sidebar

sudo gnome-desktop-item-edit /usr/share/applications/ --create-new

#Graphic driver apt-get purge nvidia* bumblebee*

Process Id

echo $$ >> $$ is defined to return the process ID of the parent in a subshell;

Show process running on ports

sudo lsof -i sudo netstat -tulpn | grep :<portNumber> >> you get processId (pid) sudo ls -la /proc/<pid>/exe >> you get the exact process

Free space under /boot

http://askubuntu.com/questions/89710/how-do-i-free-up-more-space-in-boot

#Grails bash completion https://grails.org/Grails%20Bash%20Completion http://pastebin.com/f52475980

ps -A

Manage services

/etc/init.d/ [start | stop | status] service [start | stop | status]

Enhance the system prompt

http://www.ibm.com/developerworks/linux/library/l-tip-prompt/

Environment variables

• Under /etc/profile.d/, you can create an .sh file putting together some system-wide env variables.
  • E.g. under jdk.sh you can find env variables for JVM.
• Under /etc/environment

Network

• vnstat: https://www.linuxbabe.com/monitoring/install-vnstat-debian-8ubuntu-16-04-server-monitor-network-traffic
• NetSpeed:
  • https://askubuntu.com/questions/847791/how-to-install-indicator-netspeed-in-ubuntu-16-10
  • https://github.com/GGleb/indicator-netspeed-unity

Shells

zshell

Install oh-my-zsh:
https://manuteoriginal.wordpress.com/2013/04/24/zsh-y-oh-my-zsh-en-mac-os-x/

bash

Update bashrc: . ~/.bashrc source ~/.bashrc

Copy into .bashrc:

export GIT_PS1_SHOWDIRTYSTATE=1
export PS1='\w\e[0;32m$(__git_ps1 " (%s)")\$ '

fish

• https://fishshell.com/docs/current/tutorial.html
• https://blog.devopscomplete.com/fishing-with-bob-the-fish-2decd3a2f87
  • Theme bobthefish: https://github.com/oh-my-fish/oh-my-fish/blob/master/docs/Themes.md#bobthefish
• A universal variable is a variable whose value is shared across all instances of fish, now and in the future – even after a reboot. You can make a variable universal with set -U
• Modify $PATH variable: set -U fish_user_paths <path_to_be_appended> $fish_user_paths
• Unlike other shells, fish does not have an export command. Instead, a variable is exported via an option to set, either --export or just -x.
• You can erase a variable with -e or --erase
• Unlike other shells, fish stores the exit status of the last command in $status instead of $?
• Unlike other shells, fish does not use backticks ` for command substitutions. Instead, it uses parentheses
• Unlike other shells, fish does not have aliases or special prompt syntax. Functions take their place.
  • You can see them typing functions
  • You can see the source for any function by passing its name to functions, e.g. functions ls
• Unlike other shells, there is no prompt variable like PS1. To display your prompt, fish executes a function with the name fish_prompt, and its output is used as the prompt.
• The equivalent to bashrc is ~/.config/fish/config.fish
• When fish encounters a command, it attempts to autoload a function for that command, by looking for a file with the name of that command in ~/.config/fish/functions/
  • For example, if you wanted to have a function ll, you would add a text file ll.fish to ~/.config/fish/functions
• To define aliases: $HOME/.config/fish/aliases.fish
• Show prompt in new line: set -g theme_newline_cursor yes
• To execute a bash script, several options:
  • exec bash -c "source some-bash-setup.sh; exec fish"
  • https://github.com/edc/bass