From a single DOI to multiple IGSNs

# Dataset on Biogeochemical cycling of Mg and Li isotopes in the Black Forest, Germany
uri="https://doi.org/10.5880/GFZ.3.3.2021.005"

# Similar queries:
# (1) return text, citation, ready for cut+paste into draft paper. 2-3 lines
curl -ksL "${uri}" -H "Accept: text/x-bibliography; style=apa"

# (2) return JSON, pretty-printed, with a bit more metadata
curl -ksL "${uri}" -H "Accept: application/vnd.citationstyles.csl+json"

# (2) return JSON, pretty-printed, with a bit more metadata, and list all keys of the JSON object
curl -ksL "${uri}" -H "Accept: application/vnd.citationstyles.csl+json" | jq keys_unsorted
# THESE ARE THE KEYS - top-level IGSN metadata
# [
#   "type",     "id",           "categories",
#   "author",   "contributor",  "issued",
#   "abstract", "DOI",          "publisher",
#   "title",    "URL",          "copyright"
# ]

# (3) return human-readable HTML+lots of JavaScript, complete page
curl -ksL "${uri}"

# install urifind from https://metacpan.org/pod/URI::Find
# cpanm i URI::Find
# (4) ... and extract all URLs with urifind
curl -ksL "${uri}" | urifind 

# (4) ... and extract all DOI URLs with grep
curl -ksL "${uri}" \
  | urifind \
  | grep -o -P 'https://doi.org/.+' \
  | sort -u 
  
# (5) ... and extract unique IGSN URLs
curl -ksL "${uri}" \
  | urifind -u \
  | grep 'http://igsn.org/' \
  | perl -nl -E 'say qq(<a href="$_"><code>$_</code></a>)' \
  | csvlook -H -l -t