I am on a mac and am trying to install the Google Cloud SDK (including the gcloud command line utility) using this command in terminal
curl https://sdk.cloud
In addition to the above answers, depending on your distro, it may be necessary to execute the bash command from the command line before calling your gsutil command. This is the case for distros that have tcsh or other shell as the default. By typing "bash" the source is changed to the .bashrc file and the file is executed.
# Step 1
bash
# Step 2
gsutil
#Step 3: profit!