README.md: Add a prerequisites and a hints section

diff --git a/README.md b/README.md
index f37cbaf2e647001c79ef6daf14042fc23d9e3a29..f40f599b7cdb1437201edd7a25891fdff15abce0 100644 (file)
--- a/README.md
+++ b/README.md
@@ -9,6 +9,18 @@ can make use of your preferred PDF file viewer and all of its functionality.
 The conversion is only done once and a cached PDF file gets used for subsequent
 invocations for the same topic.
 
+## Prerequisites
+
+The `pdfman` script makes use of the following tools, which need to be available
+on the local system in the default search `$PATH`:
+
+- `open`(1)
+- Either `ps2pdf`(1) of the Ghostscript suite _or_ `pstopdf`(1) which was
+  included in Apple macOS up to version 13 "Ventura".
+
+Note: `pdfman` silently falls back to "normal" `man`(1) behavior if any of the
+required tools is _not_ found.
+
 ## Usage
 
 ```bash
@@ -16,3 +28,15 @@ pdfman [-v] [-T] [<section>] <topic> ...
 pdfman <man(1) options> <arguments> ...
 pdfman {--help|--version>}
 ```
+
+- `-v`: Enable verbose output.
+- `-T`: Force regular `man`(1) behavior, don't use PDF files.
+
+### Hint
+
+You can setup an alias from `man` to `pdfman` in your shell startup files to not
+forget to use it :-)
+
+```bash
+alias man=pdfman
+```