Get the ID's for Paired-end Reads from BAM file including /1 and /2

Question

[User000]

Hello,

I want to extract the ID's from a BAM file and I use the following command line:

samtools view {input.unmerged} | cut -f 1 | awk '!x[$0]++' > {output.txt}

This is the output.txt,

HISEQ1:105:C0A57ACXX:2:1105:12172:84568
HISEQ1:105:C0A57ACXX:2:1108:17762:41110

Now, I actually want to get the FASTQ of these ID's and I use:

seqkit grep -f output.txt myfile.fastq

I actually get and empty list, when I control my FASTQ file, I realised my ID's have /1 and /2 specified.

@HISEQ1:105:C0A57ACXX:2:1105:12172:84568/1
@HISEQ1:105:C0A57ACXX:2:1108:17762:41110/2

My question is there something missing when I am extracting the ID's from BAM file? Why the output.txt doesn't have /1 and /2 specified? Amd how to solve the issue?

EDIT: May be when I extract my unmapped reads I should adjust the -f flag?

samtools view -u -f 12 -F 256 -@ {threads} {input.merged} > {output.unmapped}
-f 204? (204=12+64+128)