Convert FASTQ to FASTA using sed command

Easiest possible solution, and I believe significantly faster than awk-based methods:

sed -n '1~4s/^@/>/p;2~4p' 

The only assumption made is that each read occupies exactly 4 lines in the FASTQ file, but that seems pretty safe, in my experience.

If you find this helpful, go up-vote my answer in StackOverflow.