duplicating line with sed and cut command

Question

I have a file like entries like this:

@HWI-ST750:151:C1C6AACXX:8:1101:10000:14114/1
AAACATACCATTGCATATTTCGTATAATTCGAATTTAAGCAAGTTGTATTGCCAACAGCTCAGATCAATTAAGAATCTTTTCAAATTTATCAATTTA
+/1
DDHBFHHIAHHJEGJFGICHG;CGHGIJIIAIHHIJIGAGIE9FDFHGHG:4???BBC@8=;@FHI:DACHE>>AEAA@;B@;)6(>AC@>35@DDC
@HWI-ST750:151:C1C6AACXX:8:1101:10000:37802/1
GTTCCTTTACTTGCTCCCATGTCCCAATCTAACACACATGAGTCGTCGCACGCCAGTAAATCTAAAGATTTCAGACACTCAGACTCGTACAGTGAAA
+/1
FHHHHHJJIJJJJJJJJJJJJIJJJIJJJJJJJJJJJIHJIJ@GIHIIJJJIJHGHFFFFFFEEDEEEEDDDDDDDDDCDDCCCDDDABBDD>CC>A

I want to cut every 2nd line, from 1st to 45th word. So I used the following command:

sed "0~2p" BT8_A.fastq | cut -c1-45 | head -n 12

It worked properly but after cutting 1st 45 words th same line is getting appended to next line.Like this -

@HWI-ST750:151:C1C6AACXX:8:1101:10000:14114/1
AAACATACCATTGCATATTTCGTATAATTCGAATTTAAGCAAGTT
AAACATACCATTGCATATTTCGTATAATTCGAATTTAAGCAAGTT
+/1
DDHBFHHIAHHJEGJFGICHG;CGHGIJIIAIHHIJIGAGIE9FD
DDHBFHHIAHHJEGJFGICHG;CGHGIJIIAIHHIJIGAGIE9FD
@HWI-ST750:151:C1C6AACXX:8:1101:10000:37802/1
GTTCCTTTACTTGCTCCCATGTCCCAATCTAACACACATGAGTCG
GTTCCTTTACTTGCTCCCATGTCCCAATCTAACACACATGAGTCG
+/1
FHHHHHJJIJJJJJJJJJJJJIJJJIJJJJJJJJJJJIHJIJ@GI
FHHHHHJJIJJJJJJJJJJJJIJJJIJJJJJJJJJJJIHJIJ@GI

I am not able to solve this. Where I am going wrong here. Help me.

Thank you.

My desired output is:

@HWI-ST750:151:C1C6AACXX:8:1101:10000:14114/1
AAACATACCATTGCATATTTCGTATAATTCGAATTTAAGCAAGTT
+/1
DDHBFHHIAHHJEGJFGICHG;CGHGIJIIAIHHIJIGAGIE9FD
@HWI-ST750:151:C1C6AACXX:8:1101:10000:37802/1
GTTCCTTTACTTGCTCCCATGTCCCAATCTAACACACATGAGTCG
+/1
FHHHHHJJIJJJJJJJJJJJJIJJJIJJJJJJJJJJJIHJIJ@GI

Answer 1

如果只想每隔第二行剪切一次，而其余各行保持不变，则使用awk可能会更容易：

awk 'NR % 2 == 0 { print substr($0, 0, 45) } NR % 2 == 1 { print }' BT8_A.fastq

Answer 2

单程：

$ sed 'n;s/\(.\{45\}\).*/\1/' file

Answer 3

here is a sed one-liner:

sed -r '2~2s/^(.{45}).*/\1/' file  

output:

kent$  sed -r '2~2s/^(.{45}).*/\1/' file                                            │drwxr-xr-x 4 kent kent  160 Feb 15 16:48 pkg/
@HWI-ST750:151:C1C6AACXX:8:1101:10000:14114/1                                         │-rw-r--r-- 1 kent kent   19 Feb 15 14:06 status.xml
AAACATACCATTGCATATTTCGTATAATTCGAATTTAAGCAAGTT                                         │-rw-r--r-- 1 kent kent  18K Feb 15 16:44 tinyswitch.tgz
+/1                                                                                   │-rw-r--r-- 1 kent kent   73 Feb 15 14:06 t.sh
DDHBFHHIAHHJEGJFGICHG;CGHGIJIIAIHHIJIGAGIE9FD                                         │-rw-r--r-- 1 kent kent  18K Feb 15 16:24 tsw.tgz
@HWI-ST750:151:C1C6AACXX:8:1101:10000:37802/1                                         │-rw-r--r-- 1 kent kent 7.5K Feb 19 18:44 vimod.zsh
GTTCCTTTACTTGCTCCCATGTCCCAATCTAACACACATGAGTCG                                         │-rw-r--r-- 1 kent kent  23K Feb 19 22:09 vimrd
+/1                                                                                   │-rw-r--r-- 1 kent kent   42 Feb 17 16:00 x.txt
FHHHHHJJIJJJJJJJJJJJJIJJJIJJJJJJJJJJJIHJIJ@GI