From 24f05d05cdda3aafbb6218aa180d99a86b7e218e Mon Sep 17 00:00:00 2001
From: onceupon <nim.1111.ou@gmail.com>
Date: Wed, 29 Mar 2017 17:48:14 +0800
Subject: [PATCH] add handy environment variables

---
 README.md | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/README.md b/README.md
index cf558a8..5819df5 100644
--- a/README.md
+++ b/README.md
@@ -1327,6 +1327,15 @@ cat file|rev | cut -d/ -f1 | rev
 ((var++))
 ```
 
+##### some handy environment variables
+$0   :name of shell or shell script. &nbsp
+$1, $2, $3, ... :positional parameters. &nbsp
+$#   :number of positional parameters. &nbsp
+$?   :most recent foreground pipeline exit status. &nbsp
+$-   :current options set for the shell. &nbsp
+$$   :pid of the current shell (not subshell). &nbsp
+$!   :is the PID of the most recent background command. &nbsp
+
 
 ## System
 [[back to top](#handy-bash-oneliner-commands-for-tsv-file-editing)]