Add the "Bash: Positional parameters" page.

Author: paveloom

content/notes/Bash_Positional_parameters.md

@@ -0,0 +1,47 @@
++++
+title = "Bash: Positional parameters"
++++
+
+To parse positional parameters in Bash, you can use the `getopts` builtin.
+
+It's syntax is `getopts optstring name`, where `optstring` contains the option characters to be recognized. If a character is followed by a colon, the option is expected to have an argument, which should be separated from it by white space. `name` is the name of the variable to put the current option in. The value of an argument is stored in `OPTARG`.
+
+See [`man bash`](https://www.man7.org/linux/man-pages/man1/bash.1.html) for more information.
+
+To add support for long option names, you can make use of the `set` builtin to add a single letter option to the positional parameters if a long option is found. Here's an example of that:
+
+```bash
+function handle_args()
+{
+    for arg in "$@"; do
+        shift
+        case "$arg" in
+        "--debug") set -- "$@" '-d' ;;
+        "--help") set -- "$@" '-h' ;;
+        "--ignore") set -- "$@" '-i' ;;
+        "--name") set -- "$@" '-n' ;;
+        "--publish") set -- "$@" '-p' ;;
+        *) set -- "$@" "$arg" ;;
+        esac
+    done
+
+    while getopts ":dhin:p" opt; do
+        case $opt in
+        d) option_debug_enabled=true ;;
+        h)
+            echo "$0 usage:"
+            echo "    -d, --debug   Enable debug messages"
+            echo "    -h, --help    Show the usage message"
+            echo "    -i, --ignore  Ignore existing packages"
+            echo "    -n, --name    Build the package with this name"
+            echo "    -p, --publish Publish the packages"
+            exit 0
+            ;;
+        i) option_ignore_enabled=true ;;
+        n) option_package_name="$OPTARG" ;;
+        p) option_publish_enabled=true ;;
+        *) warn "unknown option $OPTARG" ;;
+        esac
+    done
+}
+```