Update README.md

Author: Bill W

pdf2txt/alpine/README.md

@@ -2,10 +2,16 @@
 
 [![](https://badge.imagelayers.io/bwits/pdf2txt:latest.svg)](https://imagelayers.io/?images=bwits/pdf2txt:latest 'Get your own badge on imagelayers.io')
 
-Suppose you have a pdf file named `sample.pdf` in your current folder.
+1, Suppose you have a pdf file named `sample.pdf` in ~/app folder.
 ```
-docker pull bwits/pdf2txt
-docker run -ti --rm -v $(pwd):/app pdf2txt /app/sample.pdf > sample.txt
+$ docker pull bwits/pdf2txt
+$ alias pdf2txt="docker run -ti --rm -v ~/app:/app pdf2txt"
+$ pdf2txt sample.pdf > sample.txt
 ```
-You will get the txt file named `sample.txt` in your current folder.
+You will get the txt file named `sample.txt` in ~/app folder.
 
+2, You can directly run below command to convert the pdf file in current foler.
+```
+$ docker run -ti --rm -v $(pwd):/app pdf2txt sample.pdf > sample.txt
+```
+You will get the txt file named `sample.txt` in your current folder.