From 2e02a056cc510ef7276cd675a3ae35347e46db5d Mon Sep 17 00:00:00 2001
From: Imbus <aa>
Date: Sat, 21 Feb 2026 03:57:30 +0100
Subject: [PATCH] Now also reports the size of the block device before asking
 to continue

---
 writeimg.c | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/writeimg.c b/writeimg.c
index 245e6c4..e839930 100644
--- a/writeimg.c
+++ b/writeimg.c
@@ -268,20 +268,34 @@ int main(int argc, char *argv[]) {
         exit(EXIT_FAILURE);
     }
 
-    /* Seems to be the cleanest way to check for write perm on a blockdev */
-    int fd = open(wjob.oname, O_WRONLY);
-    if (fd < 0) {
-        printf("Cannot write to \"%s\", do you have write permissions?\n", wjob.oname);
-        exit(1);
+    uint64_t device_size;
+    {
+        /* Seems to be the cleanest way to check for write perm on a blockdev */
+        int fd = open(wjob.oname, O_WRONLY);
+        if (fd < 0) {
+            printf("Cannot write to \"%s\", do you have write permissions?\n", wjob.oname);
+            close(fd);
+            exit(EXIT_FAILURE);
+        }
+
+        if (ioctl(fd, BLKGETSIZE64, &device_size) < 0) {
+            perror("ioctl");
+            close(fd);
+            exit(EXIT_FAILURE);
+        }
+
+        close(fd);
     }
-    close(fd);
 
     wjob.total_bytes = file_stat.st_size;
     assert(file_stat.st_size >= 0);
 
     if (wjob.flags & WI_WRITE)
-        printf(
-            "Writing \"%s\" (%.1f MiB) to \"%s\"\n", basename(wjob.iname), BYTES_TO_MIB(wjob.total_bytes), wjob.oname);
+        printf("Writing \"%s\" (%.1f MiB) to \"%s\" (%.1f MiB)\n",
+               basename(wjob.iname),
+               BYTES_TO_MIB(wjob.total_bytes),
+               wjob.oname,
+               BYTES_TO_MIB(device_size));
 
     if ((wjob.flags & WI_ASK) && (wjob.flags & WI_WRITE)) {
         printf("Is this okay? (y/N): ");