daemon: Make "opening file" error messages distinguishable.

* nix/libstore/build.cc (DerivationGoal::openLogFile): Customize
"opening file" error message.
* nix/libutil/hash.cc (hashFile): Likewise.
* nix/libutil/util.cc (readFile, writeFile): Likewise.

2 files changed, 3 insertions, 3 deletions

diff --git a/nix/libutil/hash.cc b/nix/libutil/hash.cc
index 7853acdd49..9ba604eb85 100644
--- a/nix/libutil/hash.cc
+++ b/nix/libutil/hash.cc
@@ -244,7 +244,7 @@ Hash hashFile(HashType ht, const Path & path)
     start(ht, ctx);
 
     AutoCloseFD fd = open(path.c_str(), O_RDONLY);
-    if (fd == -1) throw SysError(format("opening file `%1%'") % path);
+    if (fd == -1) throw SysError(format("computing hash of file `%1%'") % path);
 
     unsigned char buf[8192];
     ssize_t n;
diff --git a/nix/libutil/util.cc b/nix/libutil/util.cc
index 4d3780e3c2..82eac72120 100644
--- a/nix/libutil/util.cc
+++ b/nix/libutil/util.cc
@@ -264,7 +264,7 @@ string readFile(const Path & path, bool drain)
 {
     AutoCloseFD fd = open(path.c_str(), O_RDONLY);
     if (fd == -1)
-        throw SysError(format("opening file `%1%'") % path);
+        throw SysError(format("reading file `%1%'") % path);
     return drain ? drainFD(fd) : readFile(fd);
 }
 
@@ -273,7 +273,7 @@ void writeFile(const Path & path, const string & s)
 {
     AutoCloseFD fd = open(path.c_str(), O_WRONLY | O_TRUNC | O_CREAT, 0666);
     if (fd == -1)
-        throw SysError(format("opening file '%1%'") % path);
+        throw SysError(format("writing file '%1%'") % path);
     writeFull(fd, s);
 }