ps1go

PS1 prompt generator

Quickstart

Download the ps1go executable for your platform, place it on your shell path, and set your PS1 environment variable to call the executable with your customized template.

For example, here's an example that works with a Python virtual environment:

# .bash_profile
VENV_ACTIVE='[{{.Green}}{{.Virtualenv}}{{.Default}}]'
VENV_NOTACTIVE='{{.Dim}}{{.Dark_gray}}(no venv){{.Default}}'
VENV="{{if .Virtualenv}}$VENV_ACTIVE {{else}}$VENV_NOTACTIVE {{end}}"

export PS1="\$(ps1go "$VENV \w \$ ")"

The .Virtualenv template parameter is built into ps1go. It automatically detects whether a Python virtual environment has been activated, and if so, sets the value of {{.Virtualenv}} to be the name of the activated virtualenv.

The if-statement syntax is all built into the Go text/template package, and has its own language. Refer to that documentation to see how to use it.

Background

In your .bash_profile, you can customise your shell prompt by setting (or changing) an environment variable called PS1. You can display your current setting with the following:

$ echo $PS1

Here are a few defaults for different systems:

# Debian
PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '

# Centos/Fedora
[ "$PS1" = "\\s-\\v\\\$ " ] && PS1="[\u@\h \W]\\$ "

# Gentoo (/etc/bash/bashrc)
if [[ ${EUID} == 0 ]] ; then
    PS1='\[\033[01;31m\]\h\[\033[01;34m\] \W \$\[\033[00m\] '
else
    PS1='\[\033[01;32m\]\u@\h\[\033[01;34m\] \w \$\[\033[00m\] '
fi

The Gentoo one looks very complicated because of all those ANSI color codes. You can see more of those in the default Git bash for Windows PS1 prompt setting:

$ echo $PS1
\[\033]0;$TITLEPREFIX:$PWD\007\]\n\[\033[32m\]\u@\h \[\033[35m\]$MSYSTEM \[\033[33m\]\w\[\033[36m\]`
__git_ps1`\[\033[0m\]\n$

This is a pretty complicated prompt because, in addition of having color codes, it also runs a command __git_ps1 in the course of generating the prompt, to give additional information about the status of a git repo that you might happen to be inside.

We do the same thing, but you call ps1go instead of __git_ps1 (or any other executable).

Extended example

# Dislay current git branch - built into ps1go
BRANCH='{{.Red}}{{.Branch}}{{.Default}}'

# Virtualenv support, building up a template from smaller pieces
V1='[{{.Green}}{{.Virtualenv}}{{.Default}}]'
V0='{{.Dim}}{{.Dark_gray}}(no venv){{.Default}}'
VENV="{{if .Virtualenv}}$V1 {{else}}$V0 {{end}}"

# Current user, with own color - this uses built-in PS1 format code \u
USER="{{.Light_blue}}\u{{.Default}}"

jobscount () {
    # Example of calling a bash function from your PS1.
    local count=$(eval 'jobs -p | wc -l')
    # Conditionally emit template text if the background jobs count is
    # greater than zero
    if [ $count -gt 0 ]
    then
        echo " {{.Blue}}jobs:$count{{.Default}}"
    fi
}

fpath () {
    # Current directory, with a color, also uses built-in PS1 code \w
    echo "{{.Yellow}}\w{{.Default}}"
}

export PS1="\$(ps1go \"$USER:\h:$(fpath) $VENV$BRANCH$(jobswrite) \n$ \")"

Links

https://www.gnu.org/software/bash/manual/html_node/Controlling-the-Prompt.html#Controlling-the-Prompt