How to check if Git is installed from .bashrc

Question

I'm using Git, I've changed the following line in .bashrc, To show the current checkedout branch in prompt, when pwd is a Git Repo. Operating System I'm using is: Ubuntu 32bit

# Original PS1 Line
PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '

I'm using this line to display current branch of git repo in shell prompt, instead of, the above line.

# PS1 Line to show current Git Branch in the Prompt
PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\[\033[01;32m\]$(__git_ps1 " (%s)")\[\033[00m\]\$ '

The Problem is when I give it to friends, Shell gives error __git_ps1: command not found, while navigating between directories, as the script checks for git branch on changing directories. How do I check if Git is installed and perform the branch check only if git is installed?

Edit: As suggested by ayckoster, I cameup with the following lines of code:

if [ "$color_prompt" = yes ]; then
    git --version
    GIT_IS_AVAILABLE=$?
    if [ $GIT_IS_AVAILABLE -eq 0 ]; then
        # PS1 Line to show current Git Branch in the Prompt
        PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\[\033[01;32m\]$(__git_ps1 " (%s)")\[\033[00m\]\$ '
    else
        # Original PS1 Line
        PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
    fi
else
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
fi

Now, Everytime I open the terminal I get the git --version outputted to screen, while Git is installed, and I get the following error, while opening terminal when Git is not installed:

The program 'git' is currently not installed.  You can install it by typing:
sudo apt-get install git

How do I clear this? Thanks.

Final Edit:

This is the code I came up with finally, Feel Free to use this code in your .bashrc to display current git branch in your shell prompt

if [ "$color_prompt" = yes ]; then
    if git --version &>/dev/null; then
        # PS1 Line to show current Git Branch in the Prompt
        PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\[\033[01;32m\]$(__git_ps1 " (%s)")\[\033[00m\]\$ '
    else
        # Original PS1 Line
        PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
    fi
else
    if git --version &>/dev/null; then
        # PS1 Line to show current Git Branch in the Prompt
        PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w $(__git_ps1 "(%s)")\$ '
    else
        # Original PS1 Line
            PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
    fi
fi

Answer 1

#!/bin/bash
command -v git >/dev/null 2>&1 ||
{ echo >&2 "Git is not installed. Installing..";
  yum install git
}

Answer 2

Try to execute

git --version

Depending on the return value $? you can assume git is installed or not. If you get 0 everything is fine otherwise git is not installed. You can also test this.

This assumes everything is setup correctly and git is in your $PATH and the git command is not renamed.

Use it like this

git --version 2>&1 >/dev/null # improvement by tripleee
GIT_IS_AVAILABLE=$?
# ...
if [ $GIT_IS_AVAILABLE -eq 0 ]; then #...