grep排除模式并排除前2行

问题描述

我有一个文件，想使用grep排除模式.但我也想删除每个匹配的前2行(不包括在内).我该怎么做?

I have a file and would like to use grep to exclude a pattern. But I would also like to remove the 2 preceding lines for every match (that is excluded). How do I do this?

我尝试过的事情:

cat file.txt
Sequence: MG719312_IGHV1-8*03_Homosapiens_F_V-REGION_127..422_296nt_1_____296+0=296___     from: 1   to: 296
  Start     End  Strand Pattern                 Mismatch Sequence
    217     225       + pattern:AA[CT]NNN[AT]CN        . aacacctcc
Sequence: M99648_IGHV2-26*01_Homosapiens_F_V-REGION_164..464_301nt_1_____301+0=301___     from: 1   to: 301
  Start     End  Strand Pattern                 Mismatch Sequence
    176     184       + pattern:AA[CT]NNN[AT]CN        . aatcctaca

# With grep -v I can remove the line with pattern

grep -v "[acgt]\{3\}cc[acgt][acgt]\{3\}" file.txt
Sequence: MG719312_IGHV1-8*03_Homosapiens_F_V-REGION_127..422_296nt_1_____296+0=296___ from: 1 to: 296
Start End Strand Pattern Mismatch Sequence
217 225 + pattern:AA[CT]NNN[AT]CN . aacacctcc
Sequence: M99648_IGHV2-26*01_Homosapiens_F_V-REGION_164..464_301nt_1_____301+0=301___ from: 1 to: 301
Start End Strand Pattern Mismatch Sequence

# But using -B 2 does not work here

grep -B 2 -v "[acgt]\{3\}cc[acgt][acgt]\{3\}" file.txt
Sequence: MG719312_IGHV1-8*03_Homosapiens_F_V-REGION_127..422_296nt_1_____296+0=296___ from: 1 to: 296
Start End Strand Pattern Mismatch Sequence
217 225 + pattern:AA[CT]NNN[AT]CN . aacacctcc
Sequence: M99648_IGHV2-26*01_Homosapiens_F_V-REGION_164..464_301nt_1_____301+0=301___ from: 1 to: 301
Start End Strand Pattern Mismatch Sequence

有什么主意如何也为每场比赛都删除前2行吗?

Any ideas how to remove the 2 preceding lines as well for every match?

推荐答案

在GNU sed上进行了测试，语法/功能可能会因其他实现而有所不同

Tested on GNU sed, syntax/feature might vary with other implementations

sed -E 'N;N; /[acgt]{3}cc[acgt][acgt]{3}/d' ip.txt

• -E使用ERE，某些sed版本需要-r而不是-E
• N;N将另外两行附加到模式空间
• /[acgt]{3}cc[acgt][acgt]{3}/d如果此条件匹配，则删除
  • 请注意，这将尝试在三行中的任意位置匹配正则表达式...而且，[acgt][acgt]{3}可以简化为[acgt]{4}
  • /\n.*\n.*[acgt]{3}cc[acgt][acgt]{3}/d将限制为仅匹配第三行
  • -E use ERE, some sed versions require -r instead of -E
  • N;N append two more lines to pattern space
  • /[acgt]{3}cc[acgt][acgt]{3}/d delete if this condition matches
    • note that this would try to match the regex anywhere in the three lines... also, [acgt][acgt]{3} could be simplified to [acgt]{4}
    • /\n.*\n.*[acgt]{3}cc[acgt][acgt]{3}/d will restrict to matching only 3rd line

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