read:标准输入读取数值

#标准用法,options是可选项，variable是需要输入的值
read [-options] [variable...]
read -p "Enter one or more values > " int
read -t 10 -sp "Enter secret pass phrase > " secret_pass

代码示例

#输入单个值
#!/bin/bash
# read-integer: evaluate the value of an integer.
echo -n "Please enter an integer -> "
read int
if [[ "$int" =~ ^-?[0-9]+$ ]]; then
    if [ $int -eq 0 ]; then
        echo "$int is zero."
    else
        if [ $int -lt 0 ]; then
            echo "$int is negative."
        else
            echo "$int is positive."
        fi
        if [ $((int % 2)) -eq 0 ]; then
            echo "$int is even."
        else
            echo "$int is odd."
        fi
    fi
else
    echo "Input value is not an integer." >&2
    exit 1
fi


#输入多个值，read 命令接受到变量值数目少于期望的数字，那么额外的变量值为空，而多余的输入数据则会 被包含到最后一个变量中。
#!/bin/bash
# read-multiple: read multiple values from keyboard
echo -n "Enter one or more values > "
read var1 var2 var3 var4 var5
echo "var1 = '$var1'"
echo "var2 = '$var2'"
echo "var3 = '$var3'"
echo "var4 = '$var4'"
echo "var5 = '$var5'"

#如果 read 命令之后没有列出变量名，则一个 shell 变量，REPLY，将会包含 所有的输入
#!/bin/bash
# read-single: read multiple values into default variable
echo -n "Enter one or more values > "
read
echo "REPLY = '$REPLY'"

ifs用来控制字段分离，默认是包含一个空格，一个 tab，和一个换行符

#!/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:" $FILE)
if [ -n "$file_info" ]; then
    #<<<是一个document
    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