1 files changed, 60 insertions, 0 deletions
diff --git a/bib-extract b/bib-extract
new file mode 100755
index 0000000..52aa85b
--- /dev/null
+++ b/bib-extract
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+#!/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" "$@"