1 files changed, 62 insertions, 0 deletions
diff --git a/pkgs/build-support/setup-hooks/patch-shebangs.sh b/pkgs/build-support/setup-hooks/patch-shebangs.sh
new file mode 100644
index 000000000000..6b42291358d9
--- /dev/null
+++ b/pkgs/build-support/setup-hooks/patch-shebangs.sh
@@ -0,0 +1,62 @@
+# This setup hook causes the fixup phase to rewrite all script
+# interpreter file names (`#!  /path') to paths found in $PATH.  E.g.,
+# /bin/sh will be rewritten to /nix/store/<hash>-some-bash/bin/sh.
+# /usr/bin/env gets special treatment so that ".../bin/env python" is
+# rewritten to /nix/store/<hash>/bin/python.  Interpreters that are
+# already in the store are left untouched.
+
+addHook fixupOutput 'if [ -z "$dontPatchShebangs" ]; then patchShebangs "$prefix"; fi'
+
+patchShebangs() {
+    local dir="$1"
+    header "patching script interpreter paths in $dir"
+    local f
+    local oldPath
+    local newPath
+    local arg0
+    local args
+    local oldInterpreterLine
+    local newInterpreterLine
+
+    find "$dir" -type f -perm +0100 | while read f; do
+        if [ "$(head -1 "$f" | head -c +2)" != '#!' ]; then
+            # missing shebang => not a script
+            continue
+        fi
+
+        oldInterpreterLine=$(head -1 "$f" | tail -c +3)
+        read -r oldPath arg0 args <<< "$oldInterpreterLine"
+
+        if $(echo "$oldPath" | grep -q "/bin/env$"); then
+            # Check for unsupported 'env' functionality:
+            # - options: something starting with a '-'
+            # - environment variables: foo=bar
+            if $(echo "$arg0" | grep -q -- "^-.*\|.*=.*"); then
+                echo "unsupported interpreter directive \"$oldInterpreterLine\" (set dontPatchShebangs=1 and handle shebang patching yourself)"
+                exit 1
+            fi
+            newPath="$(command -v "$arg0" || true)"
+        else
+            if [ "$oldPath" = "" ]; then
+                # If no interpreter is specified linux will use /bin/sh. Set
+                # oldpath="/bin/sh" so that we get /nix/store/.../sh.
+                oldPath="/bin/sh"
+            fi
+            newPath="$(command -v "$(basename "$oldPath")" || true)"
+            args="$arg0 $args"
+        fi
+
+        newInterpreterLine="$newPath $args"
+
+        if [ -n "$oldPath" -a "${oldPath:0:${#NIX_STORE}}" != "$NIX_STORE" ]; then
+            if [ -n "$newPath" -a "$newPath" != "$oldPath" ]; then
+                echo "$f: interpreter directive changed from \"$oldInterpreterLine\" to \"$newInterpreterLine\""
+                # escape the escape chars so that sed doesn't interpret them
+                escapedInterpreterLine=$(echo "$newInterpreterLine" | sed 's|\\|\\\\|g')
+                sed -i -e "1 s|.*|#\!$escapedInterpreterLine|" "$f"
+            fi
+        fi
+    done
+
+    stopNest
+}