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I always try faSomeRecords, to extract. It is lil handy.
See BIOCONDA https://bioconda.github.io/recipes/ucsc-fasomerecords/README.html
You can also try this, if you have lists of ids
grep -A1 -w -f id.txt seqFile.fasta > output.fasta
Try samtools
$ samtools faidx multifile.fa
$ samtools faidx multifile.fa Seq2 > Seq2.fa