Shell基礎(四)：讀取鍵盤輸入

讀取鍵盤輸入

READ 命令

read 命令基本用法

#! /bin/bash
# 讀取多個輸入
echo "Enter some values>"
read value1 value2 value3 
echo "value1 : $value1"
echo "value2 : $value2"
echo "value3 : $value3"
輸入：a b c d e f
輸出：
    value1 : a
    value2 : b
    value3 : c d e f    // 輸入的多餘參數會被最後一個讀取變量全部接收。

$REPLY 變量: 會接收所有輸入。

#! /bin/bash
# $REPLY 讀取所有輸入
echo "Enter some values>"
read 
echo "\$REPLY : $REPLY"
輸出：a b c d e f
輸出：$REPLY : a b c d e f

read參數：

舉例1:讀取提示

#!/bin/bash
# read-single: read multiple values into default variable
read -p "Enter one or more values > "
echo "REPLY = '$REPLY'"

舉例2:限時讀取密碼

#!/bin/bash
# read-secret: input a secret pass phrase
if read -t 10 -sp "Enter secret pass phrase > " secret_pass; then
    echo -e "\nSecret pass phrase = '$secret_pass'"
else
    echo -e "\nInput timed out" >&2
    exit 1
if

IFS:讀取的數據分割符

含義：SHELL中read 按照變量IFS(內部字符分隔符)區分輸入的各個字符。默認IFS值包含一個空格，一個tab和一個換行符，每一個都會把字符串分開。

舉例：修改IFS以:區分,並讀取/ect/passwd內容，然後展示。

#!/bin/bash
# read-ifs: read fields from a file
FILE=/etc/passwd
read -p "Enter a user name > " user_name
file_info=$(grep "^$user_name:" $FILE)       # 讀取到輸入用戶名相關的passwd行。
if [ -n "$file_info" ]; then                 # 檢測匹配到的字符串行存在，且長度大於0。
    # 先設置分割符爲：然後依次讀取並賦值，注意<<< 是Here字符串，在shell中不能用管道。
    IFS=":" read user pw uid gid name home shell <<< "$file_info"  
    echo "User = '$user'"
    echo "UID = '$uid'"
    echo "GID = '$gid'"
    echo "Full Name = '$name'"
    echo "Home Dir. = '$home'"
    echo "Shell = '$shell'"
else
    echo "No such user '$user_name'" >&2
    exit 1
fi

校正輸入：

#!/bin/bash
# read-validate: validate input
invalid_input () {
    echo "Invalid input '$REPLY'" >&2
    exit 1
}
read -p "Enter a single item > "
# input is empty (invalid)
[[ -z $REPLY ]] && invalid_input
# input is multiple items (invalid)
(( $(echo $REPLY | wc -w) > 1 )) && invalid_input
# is input a valid filename?
if [[ $REPLY =~ ^[-[:alnum:]\._]+$ ]]; then
    echo "'$REPLY' is a valid filename."
    if [[ -e $REPLY ]]; then
        echo "And file '$REPLY' exists."
    else
        echo "However, file '$REPLY' does not exist."
    fi
    # is input a floating point number?
    if [[ $REPLY =~ ^-?[[:digit:]]*\.[[:digit:]]+$ ]]; then
        echo "'$REPLY' is a floating point number."
    else
        echo "'$REPLY' is not a floating point number."
    fi
    # is input an integer?
    if [[ $REPLY =~ ^-?[[:digit:]]+$ ]]; then
        echo "'$REPLY' is an integer."
    else
        echo "'$REPLY' is not an integer."
    fi
else
    echo "The string '$REPLY' is not a valid filename."
fi