.TH ESEARCH 1 2021-03-07 NCBI "NCBI Entrez Direct User's Manual"
.SH NAME
esearch \- search an NCBI Entrez database
.SH SYNOPSIS
\fBesearch\fP (\fBedirect\ \-search\fP)
[\|\fB\-help\fP\|]
\fB\-db\fP\ \fIname\fP
\fB\-q\fP\|[\|\fBuery\fP\|]\fP\ \fIstr\fP
[\|\fB\-sort\fP\ \fIfield\fP\|]
[\|\fB\-days\fP\ \fIN\fP\|]
[\|\fB\-datetype\fP\ \fIfield\fP\|]
[\|\fB\-mindate\fP\ \fIdate\fP\|]
[\|\fB\-maxdate\fP\ \fIdate\fP\|]
[\|\fB\-field\ \fIfield\fP\|]
[\|\fB\-pairs\ \fIfield\fP\|]
[\|\fB\-spell\fP\|]
.SH DESCRIPTION
\fBesearch\fP searches an NCBI Entrez database for a given query.

It has two implementations:
a shell implementation on top of \fBnquire\fP(1) and
a traditional Perl implementation that amounts to running
\fBedirect \-search\fP,
enabled by setting the environment variable \fBUSE_NEW_EDIRECT\fP
to a false value as described in the \fBENVIRONMENT\fP section.

Some options are implementation\-specific, as detailed below.
In addition, the shell implementation accepts
the full range of \fBefilter\fP(1) options,
whereas the Perl implementation accepts
only those specifically mentioned below.
.SH OPTIONS
.SS Query Specification
.TP
\fB\-db\fP\ \fIname\fP
Entrez database name.
.TP
\fB\-q\fP\ \fIstr\fP \fB(Perl implementation only)\fP
.PD 0
.TP
\fB\-query\fP\ \fIstr\fP
Query string.
.PD
.SS Document Order
.TP
\fB\-sort\fP\ \fIfield\fP
Sort results by the given field.
.SS Date Constraint
.TP
\fB\-days\fP\ \fIN\fP
Return only results from the past \fIN\fP days.
.TP
\fB\-datetype\fP\ \fIfield\fP
Which date field (in abbreviated form) to consider.
.TP
\fB\-mindate\fP\ \fIdate\fP
Start of date range.
.TP
\fB\-maxdate\fP\ \fIdate\fP
End of date range.
.SS Limit by Field
.TP
\fB\-field\fP\ \fIfield\fP \fB(Perl implementation only)\fP
Query words individually in field.
.TP
\fB\-pairs\fP\ \fIfield\fP \fB(Perl implementation only)\fP
Query overlapping word pairs.
.SS Spell Check
.TP
\fB\-spell\fP
Correct misspellings in query.
.SS Miscellaneous Arguments
.TP
\fB\-help\fP
Print usage information.
.SH ENVIRONMENT
.TP
.B USE_NEW_EDIRECT
Whether to use the current shell implementation
or revert to the historical Perl implementation.
Canonical true values are \fB1\fP, \fBon\fP (case\-insensitive),
\fBtrue\fP (case\-insensitive), and \fByes\fP (case\-insensitive);
canonical false values are \fB0\fP, \fBoff\fP (case\-insensitive),
\fBfalse\fP (case\-insensitive), and \fBno\fP (case\-insensitive).
.SH SEE ALSO
.BR edirect (1),
.BR efetch (1),
.BR efilter (1),
.BR eproxy (1),
.BR espell (1),
.BR exclude\-uid\-lists (1),
.BR intersect\-uid\-lists (1),
.BR nquire (1).