我如何用Perl提取某些行?

Question

我有这样的字符串

Modified files: ['A', 'B']
File: /tpl/src/vlan/VlanInterfaceValidator.cpp
Newly generated warnings:
A has warnings
B has warning
Status: PASS

我想要"新生成的警告:"应该是

A has warnings
B has warning

我是perl新手，不知道如何在perl中使用正则表达式。请帮助。

Answer 1

有两个选项:

• 将字符串分成行，并使用grep
过滤行数组
• 在多行字符串
上使用正则表达式

my $str = "
Modified files: ['A', 'B']
File: /tpl/src/vlan/VlanInterfaceValidator.cpp
Newly generated warnings:
A has warnings
B has warning
Status: PASS";
my @lines = grep{ /w+ has warning/ } split(/n/, $str);
print "Option 1 using split and grep:n";
print join("n", @lines);
$str =~ s/^.*Newly generated warnings:s*(.*?)s+Status:.*$/$1/sm;
print "nnOption 2 using regex:n";
print $str;

输出:

Option 1 using split and grep:
A has warnings
B has warning
Option 2 using regex:
A has warnings
B has warning

选项1的解释:

• split(/n/, $str)-将字符串拆分为字符串数组
• grep{ /w+ has warning/ }-使用grep正则表达式对感兴趣的行进行过滤
  • 注意:这是标准正则表达式测试$_ =~ /w+ has warning/的缩写。$_包含字符串元素，例如line.

选项1的说明:

• $str =~ s/search/replace/-对字符串进行标准搜索和替换
  • 注意:与许多其他语言不同，Perl
  中的字符串是可变的
• s/^.*Newly generated warnings:s*(.*?)s+Status:.*$/$1/sm:
  • 搜索:
    • ^.*-从字符串开始抓取所有内容直到:
    • Newly generated warnings:
    • s+-扫描空白
    • (.*?)-捕获组1与非贪婪扫描
    • s+Status:.*$-扫描空格，Status:和其他所有内容以结束字符串
  • 替换:
    • $1-使用捕获组1
  • 标记:
    • s-点匹配换行符
    • m-多行，例如^是字符串的开始，$是字符串的结束

Answer 2

这种问题就是你可以读到你想要的部分的那一行然后不做任何处理，然后读到你想要的部分的开头，保留这些行

# ignore all these lines
while( <DATA> ) {
last if /Newly generated warnings/;
}
# process all these lines
while( <DATA> ) {
last if /As*z/;  # stop of the first blank line
print;  # do whatever you need
}
__END__
Modified files: ['A', 'B']
File: /tpl/src/vlan/VlanInterfaceValidator.cpp
Newly generated warnings:
A has warnings
B has warning
Status: PASS

从文件句柄中读取。处理字符串非常简单，因为您可以在字符串上打开文件句柄，这样您就可以逐行处理字符串:

my $string = <<'HERE';
Modified files: ['A', 'B']
File: /tpl/src/vlan/VlanInterfaceValidator.cpp
Newly generated warnings:
A has warnings
B has warning
Status: PASS
HERE
open my $fh, '<',  $string;
while( <$fh> ) {
last if /Newly generated warnings/;
}
while( <$fh> ) {
last if /As*z/;
print;  # do whatever you need
}