# LeetCode Solution, Easy, 193. Valid Phone Numbers

# [193. Valid Phone Numbers](https://leetcode.com/problems/valid-phone-numbers/)

### 題目敘述

Given a text file `file.txt` that contains list of phone numbers (one per line), write a one liner bash script to print all valid phone numbers.

You may assume that a valid phone number must appear in one of the following two formats: (xxx) xxx-xxxx or xxx-xxx-xxxx. (x means a digit)

You may also assume each line in the text file must not contain leading or trailing white spaces.

**Example:**

Assume that `file.txt` has the following content:

    987-123-4567
    123 456 7890
    (123) 456-7890

Your script should output the following valid phone numbers:

    987-123-4567
    (123) 456-7890

#### 題目翻譯

檔案 `file.txt` 中儲存了每一行的電話資料，需要寫一個 script 來驗證每一行的電話格式，並且輸出出來。其格式有兩種 `(xxx) xxx-xxxx` 和 `xxx-xxx-xxxx`。

### 解法解析

主要解法是使用了 Regex 來去做格式判別，分別針對 `(xxx) xxx-xxxx` 和 `xxx-xxx-xxxx` 編寫各自的 Regex。

#### 解法範例

##### Bash

```bash
# Read from the file file.txt and output all valid phone numbers to stdout.
egrep -e '^\([0-9]{3}\) [0-9]{3}-[0-9]{4}$' -e '^[0-9]{3}-[0-9]{3}-[0-9]{4}$' file.txt
```