$ gunzip -c input.fastq.gz | awk '{printf("%s%s",$0,((NR+1)%4==1?"\n":"\t"));}' | head
@IL31_4368:1:1:996:8507/2 TCCCTTACCCCCAAGCTCCATACCCTCCTAATGCCCACACCTCTTACCTTAGGA + FFCEFFFEEFFFFFFFEFFEFFFEFCFC<EEFEFFFCEFF<;EEFF=FEE?FCE
@IL31_4368:1:1:996:21421/2...