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diff --git a/texnix b/texnix
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+++ b/texnix
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+#! /bin/sh
+# usage: texnix TEXFILE...
+# Print Nix expression for creating a TeX working environment for a set of
+# TEXFILEs.
+
+set -efu
+
+texnix_version=1.0.0
+
+TMPDIR=$(mktemp --tmpdir -d texnix.XXXXXXXX)
+trap 'rm -R "$TMPDIR"' EXIT
+
+# Export TMPDIR for subsequent calls to mktemp.
+export TMPDIR
+
+# usage: extract_dependencies TEXFILE...
+# Print all (transitive) dependencies of TEXFILEs.
+extract_dependencies() {(
+  all_packages=$TMPDIR/all_packages
+  dependencies=$TMPDIR/dependencies
+  working_set=$TMPDIR/working_set
+
+  get_all_packages > "$all_packages"
+  truncate -s 0 "$dependencies"
+  get_packages "$@" | comm -12 - "$all_packages" > "$working_set"
+
+  while test -s "$working_set"; do
+    package=$(pop "$working_set")
+
+    echo "$package" | add "$dependencies"
+
+    tmp_working_set=$(mktemp working_set.XXXXXXXX)
+    { cat "$working_set"
+      texlive_cat "$package" | get_packages - | comm -2 - "$dependencies"
+    } | sort -u | comm -12 - "$all_packages" > "$tmp_working_set"
+    mv "$tmp_working_set" "$working_set"
+  done
+
+  cat "$dependencies"
+)}
+
+# usage: texlive_cat PACKAGE
+# Concatenate and print all files of a TeX live package.
+texlive_cat() {
+  nix-build --no-out-link '<nixpkgs>' -A texlive."$1".pkgs |
+  while read -r path; do
+    find "$path" -mindepth 1 -maxdepth 1 -name tex -exec find {} -type f \;
+  done |
+  xargs cat
+}
+
+# usage: get_all_packages
+# Print all TeX live packages.
+get_all_packages() {
+  nix-instantiate \
+      --eval \
+      --json \
+      --strict \
+      -E \
+      'builtins.attrNames (import <nixpkgs> {}).texlive' \
+    |
+  jq -r .[] |
+  sort -u
+}
+
+# usage: get_packages TEXFILE...
+# Print all packages used in TEXFILEs.
+get_packages() {
+  sed -rn '
+    s:.*(usepackage|RequirePackage).*\{([^}]+)}:\2:;T
+    s:,:\n:g
+    p
+  ' "$@" |
+  sort -u
+}
+
+# usage: add SETFILE
+# Add lines read from stdin to SETFILE.
+add() {(
+  t=$(mktemp add.XXXXXXXX)
+  sort -u - "$1" > "$t"
+  mv "$t" "$1"
+)}
+
+# usage: pop FILE
+# Remove first line of FILE and print it to stdout.
+pop() {
+  head -1 "$1"
+  sed -i 1d "$1"
+}
+
+cat <<EOF
+# Generated with texnix $texnix_version
+{ texlive, extraTexPackages ? {} }:
+texlive.combine ({
+  inherit (texlive) scheme-small;
+  $(extract_dependencies "$@" | sed '
+    s/.*/"&" = texlive."&";/
+    2,$s/^/  /
+  ')
+} // extraTexPackages)
+EOF