Last updated: $Date: 2009-03-23 18:22:05 -0400 (Mon, 23 Mar 2009) $
EFetch documenation is also available for the Literature, and Taxonomy databases.
EFetch: Retrieves records in the requested format from a list of one or more unique identifiers.
URL ParametersExamplesUser System RequirementsEntrez DTDsDemonstration ProgramAnnouncement Mailing ListBase URL: http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi
NOTE: Utility parameters may be case sensitive. Use lower case characters for all parameters except WebEnv
Database (db)Web Environment (WebEnv)Query key (query_key)Tool (tool)E-mail address (email)Record identifier (id)Display Numbers (retstart retmax)Parameters specific to sequence databasesRetrieval mode or output formatRetrieval typeHistory link value previously returned in XML results from ESearch and used with EFetch in place of primary ID result list.
Example: WebEnv=WgHmIcDG]The value used for a history search number or previously returned in XML results from Esearch or EPost.
Example: query_key=6Note: WebEnv is similar to the cookie that is set on a user's computers when accessing PubMed on the web. If the parameter usehistory=y is included in an ESearch URL both a WebEnv (cookie string) and query_key (history number) values will be returned in the results. Rather then using the retrieved PMIDs in an ESummary URL you may simply use the WebEnv and query_key values to retrieve the records. WebEnv will change for each ESearch query.
A string with no internal spaces that identifies the resource which is using Entrez links (e.g., tool=flybase). This argument is used to help NCBI provide better service to third parties generating Entrez queries from programs. As with any query system, it is sometimes possible to ask the same question different ways, with different effects on performance. NCBI requests that developers sending batch requests include a constant 'tool' argument for all requests using the utilities.
Example: tool=flybaseIf you choose to provide an email address, we will use it to contact you if there are problems with your queries or if we are changing software interfaces that might specifically affect your requests. If you choose not to include an email address we cannot provide specific help to you, but you can still sign up for utilities-announce to receive general
announcements.
Example: email=john@doe.orgIDs required if WebEnv is not used.
Complexity regulates the display:
0 - get the whole blob1 - get the bioseq for gi of interest (default in Entrez)2 - get the minimal bioseq-set containing the gi of interest3 - get the minimal nuc-prot containing the gi of interest4 - get the minimal pub-set containing the gi of interest Example: strand=2&seq_start=50&seq_stop=2000&complexity=2Output format
output types based on database
Note: Not all Retrieval Modes are possible with all Retrieval Types.
x – retrieval mode available. Click to it to run an example * – the same content as text report but with some HTML links n/a – not available
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=nucleotide&id=5
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=nucleotide&id=5&complexity=0&rettype=fasta
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=nucleotide&id=5&rettype=gb&seq_start=1&seq_stop=9
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.cgi?db=nucleotide&id=5&rettype=fasta&seq_start=1&seq_stop=9&strand=2
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=nucleotide&id=5&rettype=gb
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=popset&id=12829836&rettype=gp
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=protein&id=8&rettype=gp
Entrez display format GBSeqXML:
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=nucleotide&id=5&rettype=gb&retmode=xml
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=protein&id=8&rettype=gp&retmode=xml
Entrez display format TinySeqXML:
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=nucleotide&id=5&rettype=fasta&retmode=xml
Entrez Gene, full display as xml: http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=gene&id=2&retmode=xml