regex - Perl Regex - 打印匹配的值

Question

打印匹配值的 perl 正则表达式是什么？例如，我想打印 195从这个字符串

"2011-04-11 00:39:28,736::[main]::INFO (Main.java:73) Test.Main::main() Total Successful Transactions = 195".

我怎样才能做到这一点？提前致谢

Answer 1

您可以在正则表达式中使用括号来捕获子字符串。捕获的组存储在 $1、$2 等中。例子:

while (<>) {
    if (/Total Successful Transactions = (\d+)/) {
        print "$1\n";
    }
}

或者，稍微短一点:

while (<>) {
    print "$1\n" if /Total Successful Transactions = (\d+)/;
}

您还可以利用列表上下文中的匹配运算符 ( // ) 返回组匹配内容的列表这一事实:

$\ = '\n'; # Output newline after each print.
while (<>) {
    print for /Total Successful Transactions = (\d+)/;
}

这使您可以编写紧凑的单行(-l 选项会自动为每个打印添加换行符等):

perl -lne 'print for /Total Successful Transactions = (\d+)/'