* The write() system call can write less than the requested

  number of bytes, e.g., in case of a signal like SIGSTOP.  
  This caused `nix --dump' to fail sometimes.

  Note that this bug went unnoticed because the call to `nix 
  --dump' is in a pipeline, and the shell ignores non-zero 
  exit codes from all but the last element in the pipeline.  
  Is there any way to check the result of the initial elements
  in the pipeline?  (In other words, is it at all possible to 
  write reliable shell scripts?)

3 files changed, 13 insertions, 3 deletions

diff --git a/corepkgs/nar/nar.sh b/corepkgs/nar/nar.sh
index 059bca8ba134..a7b6be8aaa0e 100644
--- a/corepkgs/nar/nar.sh
+++ b/corepkgs/nar/nar.sh
@@ -1,3 +1,5 @@
 #! /bin/sh
 
+echo "packing $path into $out..."
 /nix/bin/nix --dump --file "$path" | bzip2 > $out || exit 1
+
diff --git a/scripts/nix-push.in b/scripts/nix-push.in
index fdb4323038fc..bb25019e8d35 100644
--- a/scripts/nix-push.in
+++ b/scripts/nix-push.in
@@ -8,6 +8,8 @@ foreach my $id (@ARGV) {
 
     # Get all paths referenced by the normalisation of the given 
     # fstate expression.
+    system "nix -ih $id";
+    if ($?) { die "`nix -ih' failed"; }
     my @paths;
     open PATHS, "nix -qrh $id 2> /dev/null |" or die "nix -qrh";
     while (<PATHS>) {
@@ -51,6 +53,8 @@ foreach my $id (@ARGV) {
         die unless $nid =~ /^([0-9a-z]{32})$/;
 
         # Realise the Nix expression.
+	system "nix -ih $nid";
+	if ($?) { die "`nix -ih' failed"; }
         my $npath = `nix -qph $nid 2> /dev/null`;
         $? and die "creating Nix archive";
         chomp $npath;
diff --git a/src/nix.cc b/src/nix.cc
index ae016824d1f9..fe762798e799 100644
--- a/src/nix.cc
+++ b/src/nix.cc
@@ -216,8 +216,12 @@ struct StdoutSink : DumpSink
     virtual void operator ()
         (const unsigned char * data, unsigned int len)
     {
-        if (write(STDOUT_FILENO, (char *) data, len) != (ssize_t) len)
-            throw SysError("writing to stdout");
+        while (len) {
+            ssize_t res = write(STDOUT_FILENO, (char *) data, len);
+            if (res == -1) throw SysError("writing to stdout");
+            len -= res;
+            data += res;
+        }
     }
 };
 
@@ -249,7 +253,7 @@ struct StdinSource : RestoreSource
         while (len) {
             ssize_t res = read(STDIN_FILENO, (char *) data, len);
             if (res == -1) throw SysError("reading from stdin");
-            if (res == 0) throw SysError("unexpected end-of-file on stdin");
+            if (res == 0) throw Error("unexpected end-of-file on stdin");
             len -= res;
             data += res;
         }