把MySQL命令行查询结果为bash脚本变量 [英] Put results of mysql command line query into bash script variable

问题描述

我有一个真的很难搞清楚如何获得一个MySQL查询的结果为一个bash shell脚本变量。

I am having a really difficult time figuring out how to get the results of a mysql query into a bash shell script variable.

testDBName="some_database_name"
mysqlUser="root"
mysqlPassword="password"
mysqlCmd="/Applications/MAMP/Library/bin/mysql -u $mysqlUser -p $mysqlPassword -B -N"
cmdRes=$($mysqlCmd -e 'SHOW DATABASES LIKE "$testDBName"') #THIS IS THE TROUBLESOME LINE
if [ "$cmdRes" = "" ]; then
    echo "Table does not exist"
else
    echo "Table already exists"
fi

这是给我的麻烦线是cmdRes = ...。如果我只是硬code表名称为它工作得很好，是这样的：

The line that is giving me the trouble is "cmdRes=...". If I just hard-code a table name into that it works fine, like this:

cmdRes=$($mysqlCmd -e 'SHOW DATABASES LIKE "some_database_name"')

但我不能换我的头围绕如何/为什么/什么是对，当我有那个东西里面$变量去。基于解答了很多其他类似的，但是，不同的问题，我已经试过把字符串转换成不同的变量的不同部分，以减少报价，我已经试过单引号，双引号，反斜杠，双单双引号，花括号，运行的eval，等等 - 但没有什么工作

But I cannot wrap my head around how/why/what is going on when I have a $variable inside that thing. Based on answers to a lot of other similar-but-different questions, I've tried putting different portions of the string into different variables to cut down on quoting, I've tried single quotes, double quotes, backslashes, double-single-double quotes, curly braces, running eval, etc. -- but nothing is working.

感谢您的帮助，您可以提供。

Thanks for any help you can provide.

推荐答案

的问题是，外壳不会扩大单引号里的任何东西（'）

The problem is that the shell won't expand anything inside the single quotes (').

一个可能的解决方案：

cmdRes=$($mysqlCmd -e "SHOW DATABASES LIKE '$testDBName'")

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