Shell – How to Add a Function to .bash_profile/.profile/bashrc

bashfunctionprofileshell

I have a function which converts epoch time to date. Here is the definition

date1(){
  date -d @$1
}

I'd like to be able to write:

$ date1 xxxyyy

Where xxxyyy is the parameter I pass into my function so I can get the corresponding date. I understand I have to add it in either .bash_profile, .profile, or .bashrc and then source it:

$ source file

But, I'm not sure which file to put it in. Currently, I have it in .profile.
But to run it, I have to do source .profile every time.

Ideally, it should make it available, when the computer starts up like the environment variable.

Best Answer

From man bash:

When bash is invoked as an interactive login shell, or as a non-interactive shell with the --login option, it first reads and executes commands from the file /etc/profile, if that file exists. After reading that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and reads and executes commands from the first one that exists and is readable.

In other words, you can put it in any one of ~/.bash_profile, ~/.bash_login or ~/.profile, or any files sourced by either of those. Typically ~/.profile will source ~/.bashrc, which is the "personal initialization file, executed for login shells."

To enable it, either start a new shell, run exec $SHELL or run source ~/.bashrc.

Related Solutions

bash – Difference Between .profile and .bash_profile and Why .profile Might Be Missing

The .profile dates back to the original Bourne shell known as sh. Since the GNU shell bash is (depending on its options) a superset of the Bourne shell, both shells can use the same startup file. That is, provided that only sh commands are put in .profile

For example, alias is a valid built-in command of bash but unknown to sh. Therefore, if you had only a .profile in your home directory and put an alias statement in it, sh would complain. So there is a bash specific file that has shell initialization commands which bash will read if and only if there isn't a .profile file present.

Actually that's a bit of an oversimplification in some installations, and I'm not familiar with Fedora. Under bash, /etc/profile is read by the shell before any files in your home directory. If there is a system wide initialization script it often says something like

if there is a $HOME/.profile:
   source it
elseif bash is my shell and there is a $HOME/.bash_profile:
   source that

Why is that way? An attempt at compatibility across decades of shell dialects. Why is the tutorial written that way? The Bourne shell is not often used much any more and some people don't even know that there is any other Bourne-like shell than bash. Even when the (limited) Bourne syntax is used for greater cross-platform compatibility it is often being run by dash or bash in POSIX compatibility mode. Indeed, the actual Bourne shell source is probably a copyright component of Unix System V which appears to be the property of Novell now but I have no idea what, if anything, they are doing with it.

For the beginning user, use either $HOME/.profile or $HOME/.bash_profile but not both and you'll be fine. Since you already have a .bash_profile work with that because it may have system specific stuff in it that your installation needs.

Shell – How to get this script file’s functions to load without having to source it every time? “command not found” (Bash/scripting basics)

mikeserv's answer is good for the details of what goes on "behind the scenes", but I feel another answer here is warranted as it doesn't contain a simple usable answer to the exact title question:

How can I get this script file's functions to load without having to source it every time?

The answer is: Source it from your .bashrc or your .bash_profile so it is available in each shell you run.

For example, I have the following in my .bash_profile:

if [ -d ~/.bash_functions ]; then
  for file in ~/.bash_functions/*.sh; do
    . "$file"
  done
fi

Best Answer

Related Solutions

bash – Difference Between .profile and .bash_profile and Why .profile Might Be Missing

Shell – How to get this script file’s functions to load without having to source it every time? “command not found” (Bash/scripting basics)

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