Are bam2fastq --no-aligned and samtools fastq -f 4 same?

Question

[Yogesh]

hi i am trying to explore the unmapped reads of my genome assembly. I straight forward tried samtools fastq -f 4 bla.bam > unmapped.fq but it gave me single file which was unusable for contig generation using spades. So i shifted to bam2fastq --no-aligned. Although i got things working but i am not pretty sure if both approach are same and are right to extract unmapped reads only.

[Pierre Lindenbaum]

1) samtools sort -n or samtools collate must be called before samtools fastq

2)

it gave me single file wh

see option -1 and -2