1 files changed, 54 insertions, 5 deletions

diff --git a/scripts/nix-build.in b/scripts/nix-build.in
index f8cf318ff07a..ca43041b77b0 100755
--- a/scripts/nix-build.in
+++ b/scripts/nix-build.in
@@ -5,6 +5,8 @@ use strict;
 use Nix::Config;
 use Nix::Store;
 use Nix::Utils;
+use File::Basename;
+use Cwd;
 
 binmode STDERR, ":encoding(utf8)";
 
@@ -14,6 +16,7 @@ my $runEnv = $0 =~ /nix-shell$/;
 my $pure = 0;
 my $fromArgs = 0;
 my $packages = 0;
+my $interactive = 1;
 
 my @instArgs = ();
 my @buildArgs = ();
@@ -25,6 +28,8 @@ my @envExclude = ();
 
 my $myName = $runEnv ? "nix-shell" : "nix-build";
 
+my $inShebang = 0;
+my $script;
 
 my $tmpDir = mkTempDir($myName);
 
@@ -35,6 +40,29 @@ my $drvLink = "$tmpDir/derivation";
 $SIG{'INT'} = sub { exit 1 };
 
 
+# Heuristic to see if we're invoked as a shebang script, namely, if we
+# have a single argument, it's the name of an executable file, and it
+# starts with "#!".
+if ($runEnv && scalar @ARGV == 1) {
+    $script = $ARGV[0];
+    if (-f $script && -x $script) {
+        open SCRIPT, "<$script" or die "$0: cannot open ‘$script’: $!\n";
+        my $first = <SCRIPT>;
+        if ($first =~ /^\#\!/) {
+            $inShebang = 1;
+            @ARGV = ();
+            while (<SCRIPT>) {
+                chomp;
+                if (/^\#\!\s*nix-shell (.*)$/) {
+                    @ARGV = split / /, $1;
+                }
+            }
+        }
+        close SCRIPT;
+    }
+}
+
+
 for (my $n = 0; $n < scalar @ARGV; $n++) {
     my $arg = $ARGV[$n];
 
@@ -131,10 +159,11 @@ for (my $n = 0; $n < scalar @ARGV; $n++) {
         $runEnv = 1;
     }
 
-    elsif ($arg eq "--command") {
+    elsif ($arg eq "--command" || $arg eq "--run") {
         $n++;
         die "$0: ‘$arg’ requires an argument\n" unless $n < scalar @ARGV;
-        $envCommand = "$ARGV[$n]\nexit $!";
+        $envCommand = "$ARGV[$n]\nexit";
+        $interactive = 0 if $arg eq "--run";
     }
 
     elsif ($arg eq "--exclude") {
@@ -155,6 +184,18 @@ for (my $n = 0; $n < scalar @ARGV; $n++) {
         $packages = 1;
     }
 
+    elsif ($inShebang && $arg eq "-i") {
+        $n++;
+        die "$0: ‘$arg’ requires an argument\n" unless $n < scalar @ARGV;
+        my $interpreter = $ARGV[$n];
+        # Überhack to support Perl. Perl examines the shebang and
+        # executes it unless it contains the string "perl" or "indir",
+        # or (undocumented) argv[0] does not contain "perl". Exploit
+        # the latter by doing "exec -a".
+        my $execArgs = $interpreter =~ /perl/ ? "-a PERL" : "";
+        $envCommand = "exec $execArgs $interpreter $script";
+    }
+
     elsif (substr($arg, 0, 1) eq "-") {
         push @buildArgs, $arg;
     }
@@ -182,6 +223,11 @@ foreach my $expr (@exprs) {
     # Instantiate.
     my @drvPaths;
     if ($expr !~ /^\/.*\.drv$/) {
+        # If we're in a #! script, interpret filenames relative to the
+        # script.
+        $expr = dirname(Cwd::abs_path($script)) . "/" . $expr
+            if $inShebang && $expr !~ /^\//;
+
         # !!! would prefer the perl 5.8.0 pipe open feature here.
         my $pid = open(DRVPATHS, "-|") || exec "$Nix::Config::binDir/nix-instantiate", "--add-root", $drvLink, "--indirect", @instArgs, $expr;
         while (<DRVPATHS>) {chomp; push @drvPaths, $_;}
@@ -232,17 +278,20 @@ foreach my $expr (@exprs) {
             ($pure ? '' : 'p=$PATH; ' ) .
             'dontAddDisableDepTrack=1; ' .
             '[ -e $stdenv/setup ] && source $stdenv/setup; ' .
-            'if [ "$(type -t runHook)" = function ]; then runHook shellHook; fi; ' .
             ($pure ? '' : 'PATH=$PATH:$p; unset p; ') .
             'set +e; ' .
             '[ -n "$PS1" ] && PS1="\n\[\033[1;32m\][nix-shell:\w]$\[\033[0m\] "; ' .
+            'if [ "$(type -t runHook)" = function ]; then runHook shellHook; fi; ' .
             'unset NIX_ENFORCE_PURITY; ' .
             'unset NIX_INDENT_MAKE; ' .
             'shopt -u nullglob; ' .
             'unset TZ; ' . (defined $ENV{'TZ'} ? "export TZ='${ENV{'TZ'}}'; " : '') .
             $envCommand);
         $ENV{BASH_ENV} = $rcfile;
-        exec($ENV{NIX_BUILD_SHELL} // "bash", "--rcfile", $rcfile);
+        my @args = ($ENV{NIX_BUILD_SHELL} // "bash");
+        push @args, "--rcfile" if $interactive;
+        push @args, $rcfile;
+        exec @args;
         die;
     }
 
@@ -276,7 +325,7 @@ foreach my $expr (@exprs) {
     while (<OUTPATHS>) {chomp; push @outPaths, $_;}
     if (!close OUTPATHS) {
         die "nix-store killed by signal " . ($? & 127) . "\n" if ($? & 127);
-        exit $? >> 8 || 1;
+        exit ($? >> 8 || 1);
     }
 
     next if $dryRun;