How can I set the current working directory to the directory of the script in Bash?

The accepted answer works well for scripts that have not been symlinked elsewhere, such as into $PATH.

#!/bin/bash
cd "$(dirname "$0")"

However if the script is run via a symlink,

ln -sv ~/project/script.sh ~/bin/; 
~/bin/script.sh

This will cd into the ~/bin/ directory and not the ~/project/ directory, which will probably break your script if the purpose of the cd is to include dependencies relative to ~/project/

The symlink safe answer is below:

#!/bin/bash
cd "$(dirname "$(readlink -f "${BASH_SOURCE[0]}")")"  # cd current directory

readlink -f is required to resolve the absolute path of the potentially symlinked file.

The quotes are required to support filepaths that could potentially contain whitespace (bad practice, but its not safe to assume this won't be the case)

There are a lot of correct answers in here, but one that tends to be more useful for me (making sure a script's relative paths remain predictable/work) is to use pushd/popd:

pushd "$(dirname ${BASH_SOURCE:0})"
trap popd EXIT

# ./xyz, etc...

This will push the source file's directory on to a navigation stack, thereby changing the working directory, but then, when the script exits (for whatever reason, including failure), the trap will run popd, restoring the current working directory before it was executed. If the script were to cd and then fail, your terminal could be left in an unpredictable state after the execution ends - the trap prevents this.

I take this and it works.

#!/bin/bash
cd "$(dirname "$0")"
CUR_DIR=$(pwd)

Most answers either don't handle files which are symlinked via a relative path, aren't one-liners or don't handle BSD (Mac). A solution which does all three is:

HERE=$(cd "$(dirname "$BASH_SOURCE")"; cd -P "$(dirname "$(readlink "$BASH_SOURCE" || echo .)")"; pwd)

First, cd to bash's conception of the script's directory. Then readlink the file to see if it is a symlink (relative or otherwise), and if so, cd to that directory. If not, cd to the current directory (necessary to keep things a one-liner). Then echo the current directory via pwd.

You could add -- to the arguments of cd and readlink to avoid issues of directories named like options, but I don't bother for most purposes.

You can see the full explanation with illustrations here:

https://www.binaryphile.com/bash/2020/01/12/determining-the-location-of-your-script-in-bash.html