Introduction

做一个Bash的解析器，类似于IDE的代码自动对齐功能。原理不难，但是用Bash实现就是调试挺麻烦的。

Requirement

Write a bash script to indent code blocks in a bash source file.

Conditions:

• The source file will contain only printing characters, spaces, and newlines.
• The source file will contain only valid bash code. It is not necessary to check for invalid input.
• The source file will not contain function declarations.
• The source file may contain random indentation.
• The source file may contain nested blocks.
• In the source file keywords while/until/for/case/if/done/esac/elif/else/fi will be the first words on a line and will not be quoted.

Requirements:

• Read from standard input, write to standard output.
• Lines inside a while/until/for block should indented two spaces. If the blocks done is the first word on a line it should begin in the same column as the while/until/for .
• Lines inside a case block should indented two spaces. If the blocks esac is the first word on a line it should begin in the same column as the case .
• Lines inside an if block should indented two spaces. If the blocks elif/else/fi is the first word on a line it should begin in the same column as the if .
• Lines with # in the first column should not be indented.
• Lines not inside any block should not be indented.

Be sure your program includes all of the following:

• comments with your name, the date, and the assignment
• comments with instructions for using the program
• descriptive names and/or comments explaining variables & functions
• indentation of code blocks
• comments explaining any non-obvious control flow

Example

Before

# comment in first columnFinal=$(date -d "2016-05-24 16:00" "+%j")while truedoToday=$(date "+%j")Days=$((Final - Today))if (( Days >= 14 ))# comment not in first columnthen partyelif (( Days >= 2 ))then studyelif (( Days == 1 ))then panicelsebreakfisleep 8hdonevacation

After

# comment in first columnFinal=$(date -d "2016-05-24 16:00" "+%j")while truedoToday=$(date "+%j")Days=$((Final - Today))if (( Days >= 14 ))# comment not in first columnthen partyelif (( Days >= 2 ))then studyelif (( Days == 1 ))then panicelsebreakfisleep 8hdonevacation