delete files before symlinking; log error messages

The symlink() function should remove existing files before creating
symlinks, so scripts are idempotent.  Log messages when various system
calls fail (but don't make the whole script fail).

1 files changed, 21 insertions, 3 deletions

diff --git a/updater/install.c b/updater/install.c
index ad89556..aa80d75 100644
--- a/updater/install.c
+++ b/updater/install.c
@@ -86,6 +86,8 @@ char* MountFn(const char* name, State* state, int argc, Expr* argv[]) {
     } else {
         if (mount(location, mount_point, type,
                   MS_NOATIME | MS_NODEV | MS_NODIRATIME, "") < 0) {
+            fprintf(stderr, "%s: failed to mount %s at %s: %s\n",
+                    name, location, mount_point, strerror(errno));
             result = strdup("");
         } else {
             result = mount_point;
@@ -348,6 +350,7 @@ char* PackageExtractFileFn(const char* name, State* state,
 
 
 // symlink target src1 src2 ...
+//    unlinks any previously existing src1, src2, etc before creating symlinks.
 char* SymlinkFn(const char* name, State* state, int argc, Expr* argv[]) {
     if (argc == 0) {
         return ErrorAbort(state, "%s() expects 1+ args, got %d", name, argc);
@@ -364,7 +367,16 @@ char* SymlinkFn(const char* name, State* state, int argc, Expr* argv[]) {
 
     int i;
     for (i = 0; i < argc-1; ++i) {
-        symlink(target, srcs[i]);
+        if (unlink(srcs[i]) < 0) {
+            if (errno != ENOENT) {
+                fprintf(stderr, "%s: failed to remove %s: %s\n",
+                        name, srcs[i], strerror(errno));
+            }
+        }
+        if (symlink(target, srcs[i]) < 0) {
+            fprintf(stderr, "%s: failed to symlink %s to %s: %s\n",
+                    name, srcs[i], target, strerror(errno));
+        }
         free(srcs[i]);
     }
     free(srcs);
@@ -424,8 +436,14 @@ char* SetPermFn(const char* name, State* state, int argc, Expr* argv[]) {
         }
 
         for (i = 3; i < argc; ++i) {
-            chown(args[i], uid, gid);
-            chmod(args[i], mode);
+            if (chown(args[i], uid, gid) < 0) {
+                fprintf(stderr, "%s: chown of %s to %d %d failed: %s\n",
+                        name, args[i], uid, gid, strerror(errno));
+            }
+            if (chmod(args[i], mode) < 0) {
+                fprintf(stderr, "%s: chmod of %s to %o failed: %s\n",
+                        name, args[i], mode, strerror(errno));
+            }
         }
     }
     result = strdup("");