正则表达式选择价值

Question

我有正则表达式的一知半解，所以我想知道，如果你只能选择由SOX程序返回此文本的最大振幅值？在这种情况下，例如，我想只有0.712219选择

Samples read:           6615000
Length (seconds):     75.000000
Scaled by:         2147483647.0
Maximum amplitude:     0.712219
Minimum amplitude:    -0.805969
Midline amplitude:    -0.046875
Mean    norm:          0.009264
Mean    amplitude:    -0.000027
RMS     amplitude:     0.043011
Maximum delta:         0.734100
Minimum delta:         0.000000
Mean    delta:         0.008353
RMS     delta:         0.041470
Rough   frequency:         6767
Volume adjustment:        1.241

Answer 1

perl -nle 'm{Maximum amplitude:\s+(-?\d?\.?\d+)} and print $1' file

0.712219

该处理与负号和数字，那些没有数字，后面接着一个小数点和任意数量的数字。

Answer 2

我会做在AWK：

awk '/Maximum amplitude:/ { print $NF }' infile

这个滤波器通过匹配Maximum amplitude:线，然后打印该行的最后一个空间分隔的字段。

Answer 3

只打印有匹配的行，并修改该行。

sed -n '/Maximum amplitude/ s/.* //p' inputfile

Answer 4

^Maximum amplitude:\s*(-?\d\.\d+)\n

见here

• ^代表在行的开始。
• Maximum amplitude:确保你有正确的路线
• \s*零个或多个空格字符
• ( )代表捕获组 - 你想正则表达式来什么样的回报
• -?任选指减号
• \d表示一个单一的数字
• \.代表小数位
• \d+表示1个或多个数字
• \n代表换行符 - 导致换行。

这是生成的Perl的regex101.com：

use strict;

my $str = 'Samples read:           6615000
Length (seconds):     75.000000
Scaled by:         2147483647.0
Maximum amplitude:     0.712219
Minimum amplitude:    -0.805969
Midline amplitude:    -0.046875
Mean    norm:          0.009264
Mean    amplitude:    -0.000027
RMS     amplitude:     0.043011
Maximum delta:         0.734100
Minimum delta:         0.000000
Mean    delta:         0.008353
RMS     delta:         0.041470
Rough   frequency:         6767
Volume adjustment:        1.241';
my $regex = qr/^Maximum amplitude:\s*(-?\d\.\d+)\n/mp;

if ( $str =~ /$regex/g ) {
  print "Whole match is ${^MATCH} and its start/end positions can be obtained via \$-[0] and \$+[0]\n";
  # print "Capture Group 1 is $1 and its start/end positions can be obtained via \$-[1] and \$+[1]\n";
  # print "Capture Group 2 is $2 ... and so on\n";
}

# ${^POSTMATCH} and ${^PREMATCH} are also available with the use of '/p'
# Named capture groups can be called via $+{name}

Here是使用amp的命名捕获基团的例子。

^Maximum amplitude:\s*(?P<amp>-?\d\.\d+)\n