GREP或AWK：搜索每行的前N個字符，並輸出與模式匹配的周圍的行

Question

我有一個RNA-seq數據，看起來像這樣：

@J00157:85:HNNJLBBXX:5:1101:2869:15047 1:N:0:ATTACTCG+TATAGCCT
CGACGCTCTTCCGATCTGAGCTGCAGCCTCGGCCCCAGGATCCCCCTGGGGGACTGGACGCTGCTATTGATTCACGAGGCGCTCAGATCGGAAGAGCACAC
+
AAFFFJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJFJJJJJJJJJFJJJJJJFJJJJJJJJFJJJFJFJJJJJJJJJJJJJJJJ
--
@J00157:85:HNNJLBBXX:5:1101:12550:15574 1:N:0:ATTACTCG+TATAGCCT
GCTCTTCCGATCTGCTATTGATGACTGTCCTCTGTTCTTTCTTTCACAGTAGACGAGGACAGATCGGAAGAGCACACGTCTGAACTCCAGTCACATTACTC
+
AAAFFJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ
--

如果我們將@之后的所有內容視為一個部分，則只能看到第二行是實際的排序信息，1,3,4,5是后勤/質量信息。

目標是提取每行的前N（N = 35）個字符中包含“ GCTGCA”的序列（第二行信息） ，並同時輸出周圍的行（匹配的行前面1行，后面3行） 。

答案示例是

@J00157:85:HNNJLBBXX:5:1101:2869:15047 1:N:0:ATTACTCG+TATAGCCT
CGACGCTCTTCCGATCTGAGCTGCAGCCTCGGCCCCAGGATCCCCCTGGGGGACTGGACGCTGCTATTGATTCACGAGGCGCTCAGATCGGAAGAGCACAC
+
AAFFFJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJFJJJJJJJJJFJJJJJJFJJJJJJJJFJJJFJFJJJJJJJJJJJJJJJJ
--

我嘗試過的是

awk 'substr($0, 1, 35) ~ "GCTGCA"' filename.fastq > newfile.fastq
grep -B 1 -A 2 -E GCTGCA filename.fastq > newfile.fastq
awk '{a[++i]=$0;}{substr(a[++i], 1, 35) ~ "GCTGCA"}{for(j=NR-1;j<=NR+2;j++)print a[j];}' filename.fastq > newfile.fastq

第一個不能輸出周圍的線。 第二個不能將模式匹配限制在每行的前35個字母中。 第三行應該可以，但是它給了我有線輸出（顯然是不正確的）：

@J00157:85:HNNJLBBXX:5:1101:14235:1367 1:N:0:ATTACTCG+TATAGCCT
@J00157:85:HNNJLBBXX:5:1101:14235:1367 1:N:0:ATTACTCG+TATAGCCT
TCTNCTCTTCCGATCTACCCCACACACCCCCGCCGCCGCCGCCGCCGCCGCCCTCCGACGCACACCACACGCGCGCGCGCGCGCGCCGCCCCCGCCGCTCC
TCTNCTCTTCCGATCTACCCCACACACCCCCGCCGCCGCCGCCGCCGCCGCCCTCCGACGCACACCACACGCGCGCGCGCGCGCGCCGCCCCCGCCGCTCC
+
+
AAF#FJJJJJJJJFJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJFJFJJJJJJJJJJJJJJJJJJJJJFJJJJJJJJJJJJJJJFJJAJJJJJFJJJJ7JJ
AAF#FJJJJJJJJFJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJFJFJJJJJJJJJJJJJJJJJJJJJFJJJJJJJJJJJJJJJFJJAJJJJJFJJJJ7JJ
--
--

Answer 1

帶有gawk多字符RS支持。

awk -v RS='\n--' -F'\n' 'substr($2,0,35)~"GCTGCA"{print $0 RS}' file

您可以使用記錄分隔符定義記錄。

Answer 2

使用getline使用awk ：

search.awk ：

substr($0,0,35)~"GCTGCA"  {
    print p # Print the previous line ...
    print # ... , current line ...
    for(i=0;i<=2;i++) { # ... and the 3 lines following it
        getline
        print
    }
}

# Store the previous line
{ p = $0 }

這樣稱呼它：

awk -f search.awk input_file

---

或不帶正則表達式並帶有參數：

search.awk

index(substr($0,0,35), search)  {
    print l
    print
    for(i=0;i<=2;i++) {
        getline
        print
    }
}

{ l = $0 }

像這樣稱呼它

awk -v search="GCTGCA" -f search.awk input_file