From eabf1f6d74dac497ce31e3e2f441cfa25e9f74f2 Mon Sep 17 00:00:00 2001
From: "Douglas B. Rumbaugh" <doug@douglasrumbaugh.com>
Date: Sat, 6 Jun 2026 12:02:41 -0400
Subject: Initial implementation (only a few years later!)

This is pure Claude. I'd written out the plan for
this suite of scripts eons ago, but never found the
time to actual do it. Remembered it this morning,
pointed Claude at the README, and had something
that appears to work in minutes.

caveat emptor: the design is mine, but the code is
purely LLM generated at this point.
---
 bib-extract | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100755 bib-extract

(limited to 'bib-extract')

diff --git a/bib-extract b/bib-extract
new file mode 100755
index 0000000..52aa85b
--- /dev/null
+++ b/bib-extract
@@ -0,0 +1,60 @@
+#!/bin/sh
+# bib-extract - emit only the database entries cited in an aux file
+#
+# usage: bib-extract file.aux [db.bib]   (db on stdin if omitted)
+#
+# roff/refer citation sources are planned but not yet supported.
+
+usage() {
+  printf 'usage: bib-extract file.aux [db.bib]\n' >&2
+  exit 2
+}
+
+if [ -n "$BIBUTILS_LIB" ]; then
+  LIB=$BIBUTILS_LIB
+elif [ -d "$(dirname "$0")/lib" ]; then
+  LIB=$(dirname "$0")/lib
+else
+  LIB=/usr/local/share/bibutils
+fi
+
+[ $# -ge 1 ] && [ $# -le 2 ] || usage
+aux=$1
+shift
+[ -r "$aux" ] || { printf 'bib-extract: cannot read %s\n' "$aux" >&2; exit 1; }
+
+keys=$(awk '
+  # classic bibtex: \citation{key,key,...}
+  {
+    line = $0
+    while (match(line, /\\citation\{[^}]*\}/)) {
+      n = split(substr(line, RSTART + 10, RLENGTH - 11), a, ",")
+      for (i = 1; i <= n; i++)
+        if (a[i] != "")
+          print a[i]
+      line = substr(line, RSTART + RLENGTH)
+    }
+  }
+  # biblatex/biber: \abx@aux@cite{segment}{key} (older: one argument)
+  {
+    line = $0
+    while (match(line, /\\abx@aux@cite(\{[0-9]*\})?\{[^}]*\}/)) {
+      s = substr(line, RSTART, RLENGTH)
+      sub(/\}$/, "", s)
+      sub(/^.*\{/, "", s)
+      if (s != "")
+        print s
+      line = substr(line, RSTART + RLENGTH)
+    }
+  }' "$aux" | sort -u | paste -sd, -)
+
+[ -n "$keys" ] || exit 0
+
+# \nocite{*} cites everything: emit the whole database
+case ",$keys," in
+  *,\*,*) keys= invert=1 ;;
+  *) invert=0 ;;
+esac
+
+exec awk -f "$LIB/bib-parse.awk" -f "$LIB/bib-canon.awk" \
+         -f "$LIB/bib-select.awk" -v keys="$keys" -v invert="$invert" "$@"
-- 
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