Bash：Sed遇到的问题没有替换字符串，也没有清空整个文件

Question

I have a file with an SQL query in it. I'm trying to alter the value one of the WHERE clauses in the query using the result of a previous query.

So basically, I run my first query and store the result in a variable: "LAST".

Then after that, in my bash file, I have this line:

sed -i 's/^AND \`id\` \> ([0-9]+)$/AND `id` > $LAST/g' /query_resources/query.sql

As you can see, I'm attempting to use regex to find the line in my query file that resembles this...

AND `id` > 12345

...And replace the string of numbers with whatever I have stored in my variable.

The problems I'm running into is that either that line is not being changed at all, or I have even had the contents of the file - that I'm doing the search and replace on - completely emptied out.

Answer 1

您需要更改为双引号，才能将$LAST转换为其实际值，并且还需要转义+和所有`符号：

sed -i "s/^AND \`id\` > [0-9]\+/AND \`id\` > $LAST/g" /query_resources/query.sql