Makefile

@@ -21,19 +21,4 @@ clean:
 
 install: writeimg
 	install -d $(DESTDIR)$(PREFIX)/bin
-	install -d $(DESTDIR)$(PREFIX)/share/man/man1
 	install -m 0755 $< $(DESTDIR)$(PREFIX)/bin/$<
-	install -m 0644 $<.1 $(DESTDIR)$(PREFIX)/share/man/man1/$<.1
-
-# Note that this bypasses PREFIX, since
-# bash does not source /usr/local by default
-install_bash: writeimg_completion_bash.sh
-	install -d $(DESTDIR)/etc/bash_completion.d
-	install -m 0644 $< $(DESTDIR)/etc/bash_completion.d/$<
-
-uninstall:
-	rm -f $(DESTDIR)$(PREFIX)/bin/writeimg
-	rm -f $(DESTDIR)$(PREFIX)/share/man/man1/writeimg.1
-	rm -f $(DESTDIR)/etc/bash_completion.d/writeimg*
-
-.PHONY: clean install uninstall

README.md

@@ -1,17 +1,13 @@
-# WriteIMG Image Writer
+# Simple dd-like image writer with additional security checks.
 
-WriteIMG is a simple dd-like image writer with additional security checks for
+This tool verifies your image automatically. The block size is currently set to
-Linux and soon FreeBSD. It tells you what you're about to do and warns you
+1 MiB, which should be enough to avoid trouble.
-about potential problems before they occur. It also features automatic image
-verifications, and uses a suitable block size for fast and gentle writing.  
-
-Say goodbye to fried flash and overwritten bootloaders, no more footguns!
 
 ```
-WriteIMG v0.2.3, Rev. d02fc5f
+writeimg v0.2.0, Rev. 5323932-dirty
 In honor of SwePwnage - the OG disk destroyer
 Copyright (C) 2026 Imbus, BSD-2-Clause
-Build date: 2026-02-21
+Build date: 2026-02-07
 
 Usage:
    writeimg [-v] -d <device> <file.img>
@@ -21,18 +17,12 @@ Args:
    -v                  Verify only
    -d device           Target block device
    -h, --help          Print this help message
-   -n, --noconfirm     Do not ask for permission
+   -n, --noconfirm     Do not ask for premission
    -V, --version       Print version
 ```
 
-We also provide a manpage, which targets OpenBSD-level quality. Incorrect or
-outdated information is a bug.
-
 ## Testing
 
-For testing, there is a shell script "test.sh" included. It sets up a block dev
-and writes (and verifies) a bunch of nonsense to it. It boils down to:
-
 ```
 dd if=/dev/zero of=./disk.img bs=1M count=1024
 losetup -fP ./disk.img
@@ -40,75 +30,6 @@ losetup -a
 losedup -d /dev/loop0
 ```
 
-Writes to a regular files is not currently in scope, although it would simplify
-testing.
-
-## Design Considerations
-
-Most of the sanity checking is currently highly Linux specific. We should
-prefer general/posix solutions that reach **at least** FreeBSD, preferably
-OpenBSD and Solaris as well. FreeBSD did implement procfs, but its a Linux-ism
-and it has since been deprecated. I would prefer not to turn this rather simple
-code into macro-mozaic, as i've seen other similar projects do. After all, this
-is just a juiced-up dd-rewrite at its core.  
-
-**Apple products are unsupported.** Im simply not interested in ensuring
-compatibility with a walled-garden ecosystem. If *you* are, we can change that.  
-
-At the time of writing, my FreeBSD server is down for maintenance, which means
-all of my development and testing is focused on AMD64, AArch64 and AArch32
-Linux.  
-
-In the setup phase of the program, we can absolutely afford to do lots of
-sanity checking via syscalls. Between each block write, we flush the disk
-buffers. These flushes are larger (1 MiB when buffer is full) than the sector
-size (often 4k or 64k) of the flash, so as far as i know, this is a gentle way
-to write flash, and should not incur any significant performance overhead. 1
-MiB is also a multiple of the most common sector sizes. We could write it all
-with no flushing, but that would mean the progress indicator will measure
-buffered writes, which is useless.  
-
-It should be possible to induce optimal block size, but this idea has not been
-explored yet.  
-
-Currently when verifying the written data, we read from both the input file and
-the output block device and do a byte-by-byte comparison. A CRC32 is also
-calculated in the first pass of the input file read. In the second pass (the
-verification stage), we calculate the CRC32 of the block device data and
-compare that to our previous result. **This means that we currently use two
-separate methods of verification**. The program allocates **two** separate
-buffers in the startup phase for comparisons. This will change in the coming
-releases, and we will rely only on the CRC.  
-
-De-allocation is handled in the interrupt vector as well as in the 'sad-paths',
-but ultimately this program can be regarded as samurai-principled. We try to
-handle deallocation, but exit on failure and let the kernel handle the rest.  
-
-The use of a crypto-grade checksumming algorithm was considered, but was
-ultimately rejected in favour of a lookup based CRC32. Its simpler, faster and
-easier to understand (See: [crc32.h](./crc32.h)). We may include a compile-time
-option to disable the lookup table to reduce size for really small targets, but
-we speculate that those targets are already satisfied with busybox-dd.  
-
-We also considered using libudev or any of its analogues, to determine the type
-of block device (spinning or flash), but my somewhat inconclusive research
-indicates that it does not include functionality to determine the medium type
-(usb/sd/sata), which is ultimately what i would like to warn the user about.
-The libudev library is also Linux specific.  
-
-We also need completion scripts for the most common shells. This includes csh,
-bash and zsh. Should be easy enough when we set our minds to it.  
-
-See:
- - `grep -nE 'BLK[A-Za-z0-9]+' /usr/include/linux/fs.h`  
-   In particular, we're interested in BLKGETSIZE64 and BLKFLSBUF for now.
-
-We can read the device info from:
- - /sys/class/block/[name]/*
-Like:
- - /sys/class/block/[name]/device/model
- - /sys/class/block/[name]/size
-
 ## Inspiration
 
 See:

test.sh

@@ -1,72 +0,0 @@
-#!/usr/env/bin bash
-
-set -e
-# set -x # For debugging
-
-# If you ever mess this up:
-#  $ mknod /dev/loop-control c 10 237
-#  $ chmod 600 /dev/loop-control
-#  $ chown root:root /dev/loop-control
-#
-# For cleanup:
-#  $ find /dev -maxdepth 1 -type b -name 'loop[0-9]*' -exec rm -f {} \;
-
-if [ "$(id -u)" -ne 0 ]; then
-    echo "Run as root. We need permissions to write and setup a loop device."
-    exit 1
-fi
-
-DISKFILE="/tmp/disk.img"
-BINFILE="/tmp/file.bin"
-LOOPNUM=$((RANDOM % 156 + 100))
-LOOPDEV="/dev/loop${LOOPNUM}"
-
-echo "Using device: ${LOOPDEV}"
-
-cleanup() {
-    echo "Cleaning up..."
-    set +e -x
-    losetup -d ${LOOPDEV}
-    rm ${LOOPDEV}
-    rm ${BINFILE} ${DISKFILE}
-}
-
-trap cleanup EXIT INT TERM
-
-if losetup ${LOOPDEV} >/dev/null 2>&1; then
-    echo "${LOOPDEV} already in use" >&2
-    cleanup
-    exit 1
-fi
-
-if [ ! -f ${DISKFILE} ]; then
-    echo "Creating ${DISKFILE}"
-    dd if=/dev/zero of=${DISKFILE} bs=1M count=256
-fi
-
-if [ ! -f ${BINFILE} ]; then
-    echo "Creating ${BINFILE}"
-    dd if=/dev/urandom of=${BINFILE} bs=1M count=64
-fi
-
-if [ ! -e ${LOOPDEV} ]; then
-    mknod ${LOOPDEV} b 7 ${LOOPNUM} # busybox needs this
-    losetup ${LOOPDEV} ${DISKFILE}
-fi
-
-./writeimg -nd ${LOOPDEV} ${BINFILE}
-./writeimg -vnd ${LOOPDEV} ${BINFILE}
-
-./writeimg -nd ${LOOPDEV} ./writeimg
-./writeimg -vnd ${LOOPDEV} ./writeimg
-
-./writeimg -nd ${LOOPDEV} ./LICENSE
-./writeimg -vnd ${LOOPDEV} ./LICENSE
-
-# Redirect this to avoid confusion
-! ./writeimg -vnd ${LOOPDEV} ./crc32.h 2>/dev/null
-
-GREEN="\e[32m"
-RESET="\e[0m"
-
-echo -e "\n\n${GREEN}Looks good!${RESET}"

writeimg.1

@@ -1,38 +0,0 @@
-.TH WRITEIMG 1 "February 2026" "writeimg" "User Commands"
-.SH NAME
-writeimg \- Write an image to a block device
-.SH SYNOPSIS
-.B writeimg
-\fB\-d\fR \fIDEVICE\fR \fIIMAGE\fR
-.br
-.B writeimg
-\fB\-\-device\fR \fIDEVICE\fR \fIIMAGE\fR
-
-.SH DESCRIPTION
-.B writeimg
-reads the input
-.I IMAGE
-and writes its contents to
-.I DEVICE
-
-The output device must be specified explicitly using the
-.B \-d
-or
-.B \-\-device
-option. The image file is given as a positional argument.
-.SH OPTIONS
-.TP
-.BR \-d ", " \-\-device" " DEVICE
-Device to write to.
-.TP
-.BR \-n ", " \-\-noconfirm
-Do not require confirmation from user.
-.TP
-.BR \-v ", " \-\-verify
-Verify only, do not write
-.SH EXAMPLES
-Write an image to a block device:
-.PP
-.nf
-    writeimg -d /dev/sdx file.img
-.fi

writeimg.c

@@ -3,7 +3,6 @@
 #include <fcntl.h>
 #include <getopt.h>
 #include <libgen.h>
-#include <limits.h>
 #include <signal.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -42,14 +41,8 @@
 #define BAR_WIDTH 50
 
 void print_progress(int current, int total) {
-    static int last = INT_MAX;
+    float fraction = (float)current / total;
-    float      fraction = (float)current / total;
+    int   filled = (int)(fraction * BAR_WIDTH);
-    int        filled = (int)(fraction * BAR_WIDTH);
-
-    if (filled == last)
-        return; /* Avoid unnecessary io/flushes */
-
-    last = filled;
 
     printf("\r[");
     for (int i = 0; i < BAR_WIDTH; i++) {
@@ -72,7 +65,7 @@ const char help[] =
     "   -v                  Verify only\n"
     "   -d device           Target block device\n"
     "   -h, --help          Print this help message\n"
-    "   -n, --noconfirm     Do not ask for permission\n"
+    "   -n, --noconfirm     Do not ask for premission\n"
     "   -V, --version       Print version\n"
     "\0";
 // clang-format on
@@ -80,8 +73,8 @@ const char help[] =
 const char copyright[] = "Copyright (C) %s Imbus, BSD-2-Clause\n";
 
 struct write_job {
-    char  *iname;
+    char  *filename;
-    char  *oname;
+    char  *dev_name;
     char  *buffer;
     char  *buffer2; /* For memcmp integrity checks */
     size_t bufsize;
@@ -105,8 +98,8 @@ void int_handler(int signum) {
 }
 
 int perform_write(write_job_t *job) {
-    int block_fd = open(job->oname, O_RDWR);
+    int block_fd = open(job->dev_name, O_RDWR);
-    int file_fd = open(job->iname, O_RDONLY);
+    int file_fd = open(job->filename, O_RDONLY);
 
     assert(block_fd >= 0);
     assert(file_fd >= 0);
@@ -135,7 +128,7 @@ int perform_write(write_job_t *job) {
         }
 
         if (read_bytes < 0) {
-            fprintf(stderr, "%s: Read error\n", job->iname);
+            fprintf(stderr, "%s: Read error\n", job->filename);
             perror("Read");
             exit(EXIT_FAILURE);
         }
@@ -145,7 +138,7 @@ int perform_write(write_job_t *job) {
         if (job->flags & WI_WRITE) {
             ssize_t written_bytes = write(block_fd, job->buffer, read_bytes);
             if (written_bytes < 0) {
-                fprintf(stderr, "%s: Write error\n", job->oname);
+                fprintf(stderr, "%s: Write error\n", job->dev_name);
                 perror("Write");
                 exit(EXIT_FAILURE);
             }
@@ -226,13 +219,13 @@ int main(int argc, char *argv[]) {
             wjob.flags |= WI_VERIFY;
             wjob.flags &= ~WI_WRITE;
             continue;
-        case 'd': wjob.oname = optarg; continue;
+        case 'd': wjob.dev_name = optarg; continue;
         case 'h': break;
         case 'n': wjob.flags &= ~WI_ASK; continue;
         case 'V': exit(EXIT_SUCCESS);
         }
         printf("In honor of SwePwnage - the OG disk destroyer\n");
-        printf(copyright, CR_YEAR);
+        fprintf(stdout, copyright, CR_YEAR);
 #ifdef BLDDATE
         printf("Build date: %s\n", BLDDATE);
 #endif
@@ -251,55 +244,39 @@ int main(int argc, char *argv[]) {
         exit(EXIT_FAILURE);
     }
 
-    wjob.iname = argv[0];
+    wjob.filename = argv[0];
     struct stat file_stat = {0};
-    if (0 != stat(wjob.iname, &file_stat)) {
+    if (0 != stat(wjob.filename, &file_stat)) {
         printf("File does not exist...\n");
         exit(EXIT_FAILURE);
     }
 
-    if (NULL == wjob.oname) {
+    if (NULL == wjob.dev_name) {
         printf("You need to specify a device.\n");
         exit(EXIT_FAILURE);
     }
 
-    if (0 != strncmp(wjob.oname, "/dev/", 4)) {
+    if (0 != strncmp(wjob.dev_name, "/dev/", 4)) {
-        printf("\"%s\" does not appear to be a block device...\n", wjob.oname);
+        printf("\"%s\" does not appear to be a block device...\n", wjob.dev_name);
         exit(EXIT_FAILURE);
     }
 
-    uint64_t device_size;
+    /* Seems to be the cleanest way to check for write perm on a blockdev */
-    {
+    int fd = open(wjob.dev_name, O_WRONLY);
-        /* Seems to be the cleanest way to check for write perm on a blockdev */
+    if (fd < 0) {
-        int fd = open(wjob.oname, O_WRONLY);
+        printf("Cannot write to \"%s\", do you have write permissions?\n", wjob.dev_name);
-        if (fd < 0) {
+        exit(1);
-            printf("Cannot write to \"%s\", do you have write permissions?\n", wjob.oname);
-            close(fd);
-            exit(EXIT_FAILURE);
-        }
-
-#ifdef __GLIBC__
-        if (ioctl(fd, BLKGETSIZE64, &device_size) < 0) {
-#else /* With musl, ioctl's take ints, kheaders provide unsigned longs. Passes tests. */
-        if (ioctl(fd, (int)BLKGETSIZE64, &device_size) < 0) {
-#endif
-            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\" (%.1f MiB)\n",
+        printf("Writing \"%s\" (%.1f MiB) to \"%s\"\n",
-               basename(wjob.iname),
+               basename(wjob.filename),
                BYTES_TO_MIB(wjob.total_bytes),
-               wjob.oname,
+               wjob.dev_name);
-               BYTES_TO_MIB(device_size));
 
     if ((wjob.flags & WI_ASK) && (wjob.flags & WI_WRITE)) {
         printf("Is this okay? (y/N): ");

writeimg_completion_bash.sh

@@ -1,25 +0,0 @@
-_writeimg_completion() {
-    local cur prev opts
-
-    cur="${COMP_WORDS[COMP_CWORD]}"
-    prev="${COMP_WORDS[COMP_CWORD-1]}"
-
-    opts="-v -d -h --help -n --noconfirm -V --version"
-
-    # Devices
-    if [[ "$prev" == "-d" ]]; then
-        COMPREPLY=( $(compgen -W "$(ls -d /dev/sd* /dev/nvme* /dev/mmcblk* 2>/dev/null)" -- "$cur") )
-        return 0
-    fi
-
-    # Flags
-    if [[ "$cur" != -* ]]; then
-        COMPREPLY=( $(compgen -f -- "$cur") )
-        return 0
-    fi
-
-    # Files
-    COMPREPLY=( $(compgen -W "$opts" -- "$cur") )
-}
-
-complete -F _writeimg_completion writeimg