Question

如何打印匹配的行以及之前和之后的行？我现在有：

perl -lane 'print if $F[3] > 100000 && $F[2] =~ /^C$/ && print $last; $last = $_'

能够在之前打印匹配的行和行 - 但我不知道如何在之后包含行。

Answer 1

您可以使用scalar <>直接从文件中读取下一行：

perl -lane 'print, print scalar <>
                if $F[3] > 100000 && $F[2] =~ /^C$/
                && print $last;
            $last = $_' input

或者使用滑动窗口来重叠匹配：

perl -ane 'BEGIN { @b = map [], 1 .. 3 }
           sub out {
               shift @b;
               if ($b[1][3] > 100_000 && $b[1][2] =~ /^C$/) {
                   print for map $_->[-1], @b;
               }
            }
            push @b, [@F, $_];
            out()
            }{ out()  # Process the last line
           ' input

Answer 2

以下处理重叠匹配。 $N是在匹配行之前和之后打印的行数。

perl -lane'
   BEGIN { $N = 1 }
   if ($F[3] > 100000 && $F[2] =~ /^C$/) { print for splice(@buf), $_; $next=$N }
   elsif ($next) { --$next; print }
   else { push @buf, $_; splice @buf, 0, -$N }
'

由于我们知道$N = 1，我们可以将上述内容简化为以下内容：

perl -lane'
   if ($F[3] > 100000 && $F[2] =~ /^C$/) { print for splice(@buf), $_; $next=1 }
   elsif ($next) { $next=0; print }
   else { @buf = $_ }
'

Answer 3

您还可以使用// Input: v is an array of k unique elements, each in the // range [0, n) // Output: The index of v in the set of all possible such vectors. int permindex(int n, int k, int* v) { int val[n], pos[n]; // This initialization would probably have been better as // for (int i = 0; i < n; ++i) val[i] = pos[i] = i; // The "optimization" below is intended to show that this // entire operation is O(k) rather than O(n); it involves // only initializing elements in the val and pos arrays which // we might actually reference. for (int i = 0; i < k; ++i) { val[i] = i; pos[v[i]] = v[i]; } int index = 0; for (int i = 0; i < k; ++i) { int loc = pos[v[i]]; index *= n - i; index += loc - i; pos[val[i]] = loc; val[loc] = val[i]; } return index; }和seek并重绕一行以重叠匹配：

tell

在正则表达式匹配时打印匹配的线和线±1（1线）

3 个答案: