Scroll to navigation

ESEARCH(1) NCBI Entrez Direct User's Manual ESEARCH(1)


esearch - search an NCBI Entrez database


esearch (edirect -search) [-help] -db name -q[uery] str [-sort field] [-days N] [-datetype field] [-mindate date] [-maxdate date] [-field field] [-pairs field] [-spell]


esearch searches an NCBI Entrez database for a given query.

It has two implementations: a shell implementation on top of nquire(1) and a traditional Perl implementation that amounts to running edirect -search, enabled by setting the environment variable USE_NEW_EDIRECT to a false value as described in the ENVIRONMENT section.

Some options are implementation-specific, as detailed below. In addition, the shell implementation accepts the full range of efilter(1) options, whereas the Perl implementation accepts only those specifically mentioned below.


Query Specification

Entrez database name.
Query string.

Document Order

Sort results by the given field.

Date Constraint

Return only results from the past N days.
Which date field (in abbreviated form) to consider.
Start of date range.
End of date range.

Limit by Field

Query words individually in field.
Query overlapping word pairs.

Spell Check

Correct misspellings in query.

Miscellaneous Arguments

Print usage information.


Whether to use the current shell implementation or revert to the historical Perl implementation. Canonical true values are 1, on (case-insensitive), true (case-insensitive), and yes (case-insensitive); canonical false values are 0, off (case-insensitive), false (case-insensitive), and no (case-insensitive).


edirect(1), efetch(1), efilter(1), eproxy(1), espell(1), exclude-uid-lists(1), intersect-uid-lists(1), nquire(1).

2021-03-07 NCBI