随机抽取基因组.fasta的1/3

Question

我有一个约2 gb的基因组，由支架组成 我会随机取样基因组。

我使用了formatat.sh，但是输出只是一个脚手架。我需要整个基因组的1/3 ...

>LGKD01000001.1 Octopus bimaculoides isolate UCB-OBI-ISO-001 Scaffold4_contig_1, whole genome shotgun sequence
GAACAGCATGAATGTTAAAACtgaaatggatgatgatgatgatgatgatgatgatgatggcagcaacAGCCatgattatatttaatatgttgttagttataatcataataatgatgataatgttgataacaaTAATGGTTGCAATAATG
>KQ415657.1 Octopus bimaculoides isolate UCB-OBI-ISO-001 unplaced genomic scaffold Scaffold5, whole genome shotgun sequence
tatatatatatagtcaattcgagGATGTTAGATCGACAATGGGGATTATAGAATCCCACAAAAAATTCCACTGGT
>LGKD01000032.1 Octopus bimaculoides isolate UCB-OBI-ISO-001 Scaffold12_contig_1, whole genome shotgun sequence
GAAGTGGTAAAGAGTgcgatgcgctgaaaaaagagagaacagtacttgaaatGTGGTTTCATTCTagtagtaaat
>LGKD01000033.1 Octopus bimaculoides isolate UCB-OBI-ISO-001 Scaffold16_contig_1, whole genome shotgun sequence
ctgaTCAACAGAatagggccaatcattcttcatgacaatgctcgaccacacgttttaCTAATGA
>LGKD01000034.1 Octopus bimaculoides isolate UCB-OBI-ISO-001 Scaffold22_contig_1, whole genome shotgun sequence
TTATCTATATACGagaatattatctatatataaaggaataccaaaaaaacaagaacaacgggtcattcggaattttcttt

有脚本可以做到吗？