bennythejudge · March 28, 2019 08:15 · Aug 17, 2017
diff --git a/pipefail_examples.sh b/pipefail_examples.sh
@@ -0,0 +1,47 @@
+#!/bin/bash 
+# author: Yoram van de Velde ( [email protected] )
+
+# Examples of why pipefail is really important to use.
+
+# We enable exit on error functionality
+set -o errexit
+
+# These commands will fail but not stop the script because of the pipes
+# to succesfull commands. This works because error is output to stderr,
+# and the empty output of the command is output to stdout. This means the
+# *head* command is executed with no input, but it will exit with 
+# succesfull status of 0.
+echo "set -e / set -o errexit test 1"
+no-way-this-exists | head -n 1 
+echo -e "${?}\n"
+
+echo "set -e / set -o errexit test 2"
+not_existing_command -y | cut -d ' ' -f 1
+echo -e "${?}\n"
+
+echo "set -e / set -o errexit test 3"
+really_not_existing_command | tail -n 1
+echo -e "${?}\n"
+
+
+
+# Let's set the magic pipefail and see what happens.
+set -o pipefail
+
+# If you want to allow commands in piped commands to fail you could  
+# use the following construction. This way you make sure you always
+# have expected behaviour.
+echo "set -o pipefail test 1"
+no-way-this-exists | head -n 1 || true
+echo -e "${?}\n"
+
+# All other piped commands fail and exit the script with a non zero
+# status code.
+echo "set -o pipefail test 2"
+nonexisting_command -y | tail -n 1
+echo -e "${?}\n"
+
+# We will never get here.
+echo "set -o pipefail test 3"
+nonexisting_command | head -n 1
+echo -e "${?}\n"