One trick I like to use, since I develop on multiple computers, is to define my .bash_profile in a shared place (such as Dropbox), and setup a symlink to it on the each of my computers. This works great, even when I have slightly different configurations for each computer, because my configuration only lives in one place and I conditionally target each class of computer. Today’s article describes some of my tips and tricks for bash profiles and how to conditionally target profiles for specific computers.

Getting ready

Setup a bash profile on a shared resource and symlink to it:

touch <PATH_TO_SHARED_RESOURCE_DIR>/.bash_profile
ln -s <PATH_TO_SHARED_RESOURCE_DIR>/.bash_profile ~/.bash_profile

Now open the file up in your favorite editor and begin setting up your environment. Mostly, you’ll be setting up aliases and exporting variables. The more experienced basher may even setup some functions.

The Basics: Aliases and Exports

Use export to define environment variables, such as unix variables and paths to important directories. The following ensures that bash runs in UTF-8:

# LANGUAGE SUPPORT
export LC_ALL=en_US.UTF-8
export LC_CTYPE=en_US.UTF-8
export LANG=en_US.UTF-8
export LANGUAGE=en_US.UTF-8

Here I initialize some paths that I frequently use ($HOME is defined automatically for you):

# COMMON DIRECTORIES
export DOCUMENTS_HOME=$HOME/documents
export DOWNLOADS_HOME=$HOME/downloads
export PROJECTS_HOME=$HOME/projects

Use alias to define shortcuts for common commands or a series of commands. Here are a couple examples:

alias la="ls -la"
alias dir="ls -la"
alias flushhost="dscacheutil -flushcache"
alias sshmatt="ssh mattsnider.com"
alias venv="source /usr/local/bin/virtualenvwrapper.sh"

Here is a more complicated alias that moves to a directory and initializes a python environment:

alias tblog="venv && workon mattsniderdotcom && cd ${PROJECTS_HOME}/mattsniderjsblog"

Always use && between commands, instead of ; so that the right command only executes if the left command was successful.

One of the most important environment variables is the PATH, which tell bash where to search for executables. The PATH is a colon (:) separated list of directories. I recommend creating a $HOME/bin directory for custom executables and adding it to your path:

export PATH="$HOME/bin:${PATH}"

Always, make sure you are appending or prepending to the existing PATH and not replacing it, or bad things will happen.

To append to the PATH only when the new path exists and doesn’t already exist in the list, use the following template:

TMP=""
if [[ -d $TMP ]] && [[ ! "$PATH" =~ $TMP ]];
then
	PATH="${PATH}:${TMP}"
fi

Importing Other Profiles Conditionally

To import (source) another bash profile into the current:

source "<PATH_TO_PROFILE_TO_ALSO_SOURCE>"

I like to break up my bash profiles logically, so .bash_profile only contains settings needed for all computer, then .dev_profile contains development specific settings, and .work_profile contains settings only needed for work. All these profiles are siblings in the same shared dropbox folder, but only .bash_profile has a symlink to my HOME directory. Therefore, we need to determine the directory of the dropbox symlink, so we can locate the other profiles:

TMP=$(readlink $HOME/.bash_profile)
DROPBOX_HOME=$(dirname ${TMP})

This code follows the symlink, storing it as the temporary variable TMP. It then determines the directory of TMP and stores it as the temporary variable DROPBOX_HOME. We can now source .dev_profile using:

source "$DROPBOX_HOME/.dev_profile"

However, my home computer should not source .work_profile, so .work_profile is conditionally sourced:

if [ -d "/work" ];
then
	. "$DROPBOX_HOME/.work_profile"
fi

Rather than setting a custom environment variable to target conditional imports, always use something that is unique to the computer, such as the HOSTNAME or a directory (think of this detection like feature detection in JavaScript).

Conclusion

There is a lot that can be configured in the bash profile. Use it to make your life easier. Splitting bash profiles into logical units makes maintaining them easier and keeps each file size more manageable. Using conditional sourcing, allows targeting setups to specific machines or class of machines, and generally makes loading the bash profile faster. Lastly, storing bash profiles in a shared location, makes them available no matter what computer you are on and migrating to a new system is much easier.