esearch
Perform a new Entrez search using terms in indexed fields.
TLDR
Search the pubmed database for selective serotonin reuptake inhibitor
$ esearch -db pubmed -query "[selective serotonin reuptake inhibitor]"
Search the protein database using a query and regexp
$ esearch -db [protein] -query ['Escherichia*']
Search the nucleotide database for sequences whose metadata contain insulin and rodents
$ esearch -db nuccore -query "[insulin [PROT] AND rodents [ORGN]]"
Display [h]elp
$ esearch -h
