Handle errors from write()

Fixes #964

client/powerline.c

@@ -120,7 +120,30 @@ int main(int argc, char *argv[]) {
 			close(sd);
 			HANDLE_ERROR("read() failed");
 		} else if (i > 0) {
-			(void) write(STDOUT_FILENO, buf, (size_t) i);
+			ptrdiff_t written = 0;
+			const char *bufp = &(buf[0]);
+			while (written < i) {
+				written = write(STDOUT_FILENO, buf, (size_t) i);
+				if (written >= 0) {
+					bufp += written;
+					i -= written;
+					written = 0;
+				} else {
+					errno = 0;
+					switch (errno) {
+						case EAGAIN:
+#if EAGAIN != EWOULDBLOCK
+						case EWOULDBLOCK:
+#endif
+						case EINTR:
+							break;
+						default:
+							(void) printf("Error while writing output: %s", strerror(errno));
+							close(sd);
+							return 2;
+					}
+				}
+			}
 		}
 	}