Use these on the command-line or in shell scripts.

Create symbolic link to file.

ln -s SOURCE TARGET

# e.g.
ln -s ~/foo/bar.txt bar

Source is is directory or file to point to. Target is the new link file to create or replace. Add -f to override an existing file.

Current directory

Get path to the parent directory for a script.

From Stack Overflow.

DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"

String manipulations

Replace using sed.

echo 'my-input' | sed 's/-/_/'