install-couchdb | Simple CouchDB 2.x installation script | Database library

|| is not a pipe operator. It is a shell operator meaning "or". It only executes the following command if the preceding command fails. Since true always succeeds, and otherwise does nothing, the only point of || true is to ensure that the compound command succeeds.

Normally this is unnecessary, but you can put the shell into terminate-on-failure mode with set -e. In that case, any script command which fails will cause the script to immediately terminate. (This is sometimes done in order to avoid having to check the status of every command, but it is not generally recommended as best practice.)

With set -e, it is sometimes desirable to ignore failure for certain commands (such as apt-get update); appending ||true to such a command will guarantee success and allow the script to continue even if the update fails.