How can I get iTerm to use the newer version of bash that brew shows? Change a user's shell on OSX

bash --version (or bash -version) will NOT report the CURRENT shell's version, but the version of the bash executable that comes FIRST IN THE $PATH.

[Note: OSX 10.10 (Yosemite) is the first OSX version where /usr/local/bin is placed BEFORE system paths such as /bin in the $PATH. Up to 10.9, system paths came first. Thus, at the time the OP asked his question, bash --version reported the SYSTEM's bash's version (/bin/bash), not the Homebrew-installed version (/usr/local/bin/bash)]

If you want to know the current Bash shell's version, use:

echo $BASH_VERSION

In other words: your shell may well have been changed successfully - your test was flawed.

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You can use chsh to change the current user's shell, as follows:

[Update: Switched to using /usr/local/bin/bash rather than a specific, versioned path in /usr/local/Cellar/bash/<version>/bin/bash, as Homebrew will automatically keep the symlink at /usr/local/bin/bash pointed to the most recent installed version. Tip of the hat to @drevicko.]

 # First, add the new shell to the list of allowed shells.
sudo bash -c 'echo /usr/local/bin/bash >> /etc/shells'
 # Change to the new shell.
chsh -s /usr/local/bin/bash 

Note that you'll be prompted for your password.
Any terminal tab/window you create from that point on will already use the new shell.

Bonus tip from @bmike: If you want to replace the current shell instance with an instance of the new shell right away, run:

exec su - $USER  # instantly replaces current shell with an instance of the new shell

Note that you'll be prompted for your password again.

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Alternatively, use dscl - the OSX Directory Services CLI - to change the current user's shell; this is more cumbersome, however.

To examine the current user's shell, use:

dscl . -read /Users/$USER UserShell  # e.g. (default): 'UserShell: /bin/bash'

or, more simply, echo $SHELL, which outputs only the file path (e.g., /bin/bash).

To change the current user's shell to, e.g., /usr/local/bin/bash, use:

sudo dscl . -change /Users/$USER UserShell /bin/bash /usr/local/bin/bash

Note:

• the penultimate argument must be the value currently in effect.
• it is NOT necessary for the new value to be contained in /etc/shells for interactive use, but the comments in /etc/shells state Ftpd will not allow users to connect who are not using one of these shells.
• simply quit and restart Terminal.app (or iTerm.app) for the change to take effect - verify the new shell with echo $BASH_VERSION - a reboot is NOT required.

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Explanation of errors encountered by the OP:

• chsh: /usr/local/Cellar/bash/4.2.45/bin/bash: non-standard shell implies that /usr/local/Cellar/bash/4.2.45/bin/bash was not - not yet, or not in this exact form - listed in /etc/shells.
• <main> attribute status: eDSAttributeNotFound: this dscl error occurs when the penultimate (next-to-last) argument specified for the -change command does not match the current attribute value - it is an - admittedly strange - requirement that an attribute's current value be specified in order to change it.

While the question suggests that both conditions were met, I suspect that they weren't met at the right times, due to experimentation.

The answer was that, yes, I needed to:

• brew install bash
• add the path to /etc/shells
• use chsh -s: chsh -s /usr/local/Cellar/bash/4.2.45/bin/bash

• possibly use dscl to set the shell, i.e. within dscl type

  > change Local/Default/Users/<username> UserShell /bin/bash /usr/local/bin/zsh

most importantly:

• quit the terminal (really close the app, not just its windows).
• reboot

echoing $BASH_VERSION after rebooting showed 4.2.45(2)-release