Customizing the prompt in OSX (or anything running bash)

Quick and dirty article whose only claim to fame is to show another example of treating a Mac running OSX a UNIX box: I have two Mac, an old Mini and a MacBook Air (I think I talked about it before). If you have been reading this blog, you expect me to use the shell a lot in them, and you would be right. One thing that annoys me is the default prompt used in both. The old, slow mini has the most useless one:

bash-3.2$ bash --version
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin15)
Copyright (C) 2007 Free Software Foundation, Inc.
bash-3.2$

Why would I care about knowing at all times which bash version I am running, and even then it is incomplete info (compared to bash --version)? The MacBook Air is just slightly better, showing (in order) the name of the machine, the path, and then the username.

littleguy:~ raub$

It is similar in content to what I would see in my Linux boxes,

raub@desktop:~$

but I do not like the order; it does not flow right in my eyes. So I am going to change both to look more like Linux.

First let's see how those prompts are defined in both machines; that is found by looking at the content of the environment variablePS1:

bash-3.2$ echo $PS1
\s-\v\$
bash-3.2$

and

littleguy:~ raub$ echo $PS1
\h:\W \u\$
littleguy:~ raub$

From the official gnu page on controlling the Bash prompt, we know that

• \h : hostname
  
• \s : shell name
  
• \u : username
  
• \v : shell version
  
• \w : current working directory
  
• \$ : the generic symbol for users (as opposite to # for root)
  

Based on the above, what I really want is something like PS1="\u@\h:\w\$ ". So let's try it out without permanently committing to it

bash-3.2$ PS1="\u@\h:\w\$ "
raub@slowmac:~$ 

That seems to be exactly what I want. And, since it only exists in memory (i.e. did not commit it), if I did not like it, restarting the shell or opening a new tab in iTerm would brought it back to the original config. So, how do we make it permanent? In the slowmac, we have

raub@slowmac:~$ cat ~/.bash_profile
# .bash_profile

# Get the aliases and functions
if [ -f ~/.bashrc ]; then
        . ~/.bashrc
fi

# User specific environment and startup programs

PATH=$PATH:$HOME/bin:/opt/local/bin:/opt/local/sbin

export PATH

raub@slowmac:~$

So we might as well put it in the .bashrc file the lazy way.

cat >> ~/.bashrc << "EOF"
PS1="\u@\h:\w\$ "
EOF

Interestingly enough, the MacBook Air does not have a ~/.bash_profile. Maybe the slowmac did not have it either and I added it because I was developing programs in it a while ago. No problem, we can solve the MacBook Air problem by creating a ~/.bash_profile or just appending the proper lines to it, which is done the same was as we did to add the prompt lines to the slowmac's .bashrc:

cat >> ~/.bash_profile << "EOF"

# Get the aliases and functions
if [ -f ~/.bashrc ]; then
        . ~/.bashrc
fi
EOF

Why do we put the prompt in the .bashrc instead of .bash_profile. You see, while ~/.bash_profile is executed when you login, ~/.bashrc is run whenever you start a new shell. By having our prompt defined in ~/.bashrc and then having ~/.bashrc called by ~/.bash_profile we cover our bases.

I am happy, but if you want to make your prompt fancier with colour and cows (really), I would suggest you to check a few more articles such as

• Prompt Customization
• How to Make a Fancy and Useful Bash Prompt in Linux

In addition to the gnu page I mentioned above. Incidentally, everything I mentioned above should work with any Linux and UNIX distro using bash