add entry on functions in bash

Programming_Languages/Shell/Functions_in_Bash.md

@@ -0,0 +1,26 @@
+---
+categories:
+  - Programming Languages
+tags:
+  - shell
+---
+
+# Functions in Bash
+
+- We don't name function parameters in the function declaration. Instead we have an implied index of arguments: `$1, $2, $3,...`. When the function is called, the first value after the function name becomes `$1` by default.
+
+```bash
+function expandRange() {
+    declare -a expandedRange=()
+    for (( i=$1; i<=$2; i++ )); do
+        expandedRange+=($i)
+    done
+    echo "${expandedRange[@]}"
+}
+```
+
+```bash
+expandedRange=$(expandRange 1 4)
+echo $expandedRange
+# 1 2 3 4
+```