bash脚本变量的作用域问题 [英] Bash Script Variable Scope Issue

问题描述

username="hello"
password="3333"

function login {
    # 1 - Username
    # 2 - Password
    match=0
    cat LoginsMaintMenu.txt | while read line; do
            x=`echo $line | awk '{print $1}'`
            y=`echo $line | awk '{print $2}'`
            if [ "${x}" == "${1}" ] && [ "${y}" == "${2}" ]; then
                    echo "match"
                    match=1
                    echo $match
                    break
            fi
    done
    echo $match
    return $match
}

echo $username $password
login ${username} ${password}
if [ $? -eq 0 ]; then
echo "FAIL"
else
echo "success"
fi

输出：

hello 3333
match
1
0
FAIL

问题：
我不明白为什么它呼应不及格。在匹配变量被设置为1，while循环中，但由于某些原因，一旦我出了while循环，它仍然认为它是从它的声明初始零的。

THE PROBLEM: I don't understand why it is echoing "fail". the "match" variable gets set to 1 inside the while loop, but for some reason once I am out of the while loop it still thinks it is the initial zero from its declaration.

我曾尝试做很多不同的事情，因此，如果有人可以给我一些具体的尝试会是伟大的！

I have tried doing a lot of different things, so if someone could give me something concrete to try that'd be great!

感谢

推荐答案

究其原因，这是不工作实际上是的 UUOC 。在bash中，管道的右侧是一个子shell的冲了进去。一个子壳内部设置的任何变量将不会在父shell进行设置。为了解决这个问题，可以使用，而不是一个管道重定向：

The reason that this is not working is actually the UUOC. In bash, the right side of a pipeline is ran inside of a sub-shell. Any variables set inside of a sub shell will not be set in the parent shell. To fix this, use redirection instead of a pipeline:

username="hello"
password="3333"

function login {
    # 1 - Username
    # 2 - Password
    match=0
    while read x y _; do
        if [ "${x}" == "${1}" ] && [ "${y}" == "${2}" ]; then
            echo "match"
            match=1
            echo $match
            break
        fi
    done < LoginsMaintMenu.txt
    echo $match
    return $match
}

echo $username $password
if login "${username}" "${password}"; then
    echo "FAIL"
else
    echo "success"
fi

这篇关于bash脚本变量的作用域问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！