post: bash boolean string statements

collections/_posts/2022-02-08-parsing-boolean-string-statements-in-bash.md

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+---
+layout: post
+title:  "Parsing boolean string statements in bash"
+date:   2022-02-08 14:57:08 +0100
+categories: bash
+excerpt: How to convert yes, no, true and false into a boolean in bash.
+#proccessors: pymd
+---
+
+## Preface
+
+While writing a custom GitHub Action with a Docker entrypoint written in bash,
+I want the users to be able to pass boolean variables as `true` and `false`,
+`yes` and `no`, `1` and `0`, and en empty string being considered false.
+
+## Using a function with a regular expression
+
+I first went with `return 0` and `return 1` in the function,
+but I found this to increase my cognitive load due to `0` being success, i.e.
+true, and `1` being false. I found that returning a string gives for easier reading.
+
+```bash
+# Returns a string `true` if the string is considered a boolean true,
+# otherwise `false`. An empty value is considered false.
+function str_bool {
+  local str="${1:-false}"
+  local pat='^(true|1|yes)$'
+  if [[ "$str" =~ $pat ]]
+  then
+    echo 'true'
+  else
+    echo 'false'
+  fi
+}
+```
+
+I can now configure my variables as booleans!
+
+```bash
+enable_debug_logging=$(str_bool "${ENABLE_DEBUG_LOGGING:-}")
+
+if [ "$enable_debug_logging" = "true" ]
+then
+  # ...
+  echo "Debug logging enabled!"
+fi
+```