tftp: optional tftp-hpa compat
[oweals/busybox.git] / coreutils / dd.c
index fd4e7e8a2a0fcf334c57c076b0c29d4183ffe147..b5f3cbec5d4aa4297a97f18d9dc5fd99dabf073c 100644 (file)
 /*
  * Mini dd implementation for busybox
  *
- *
  * Copyright (C) 2000,2001  Matt Kraai
  *
- * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
+//config:config DD
+//config:      bool "dd (7.5 kb)"
+//config:      default y
+//config:      help
+//config:      dd copies a file (from standard input to standard output,
+//config:      by default) using specific input and output blocksizes,
+//config:      while optionally performing conversions on it.
+//config:
+//config:config FEATURE_DD_SIGNAL_HANDLING
+//config:      bool "Enable signal handling for status reporting"
+//config:      default y
+//config:      depends on DD
+//config:      help
+//config:      Sending a SIGUSR1 signal to a running 'dd' process makes it
+//config:      print to standard error the number of records read and written
+//config:      so far, then to resume copying.
+//config:
+//config:      $ dd if=/dev/zero of=/dev/null &
+//config:      $ pid=$!; kill -USR1 $pid; sleep 1; kill $pid
+//config:      10899206+0 records in
+//config:      10899206+0 records out
+//config:
+//config:config FEATURE_DD_THIRD_STATUS_LINE
+//config:      bool "Enable the third status line upon signal"
+//config:      default y
+//config:      depends on DD && FEATURE_DD_SIGNAL_HANDLING
+//config:      help
+//config:      Displays a coreutils-like third status line with transferred bytes,
+//config:      elapsed time and speed.
+//config:
+//config:config FEATURE_DD_IBS_OBS
+//config:      bool "Enable ibs, obs, iflag, oflag and conv options"
+//config:      default y
+//config:      depends on DD
+//config:      help
+//config:      Enable support for writing a certain number of bytes in and out,
+//config:      at a time, and performing conversions on the data stream.
+//config:
+//config:config FEATURE_DD_STATUS
+//config:      bool "Enable status display options"
+//config:      default y
+//config:      depends on DD
+//config:      help
+//config:      Enable support for status=noxfer/none option.
+
+//applet:IF_DD(APPLET_NOEXEC(dd, dd, BB_DIR_BIN, BB_SUID_DROP, dd))
+
+//kbuild:lib-$(CONFIG_DD) += dd.o
+
+//usage:#define dd_trivial_usage
+//usage:       "[if=FILE] [of=FILE] [" IF_FEATURE_DD_IBS_OBS("ibs=N obs=N/") "bs=N] [count=N] [skip=N] [seek=N]\n"
+//usage:       IF_FEATURE_DD_IBS_OBS(
+//usage:       "       [conv=notrunc|noerror|sync|fsync]\n"
+//usage:       "       [iflag=skip_bytes|fullblock] [oflag=seek_bytes|append]"
+//usage:       )
+//usage:#define dd_full_usage "\n\n"
+//usage:       "Copy a file with converting and formatting\n"
+//usage:     "\n       if=FILE         Read from FILE instead of stdin"
+//usage:     "\n       of=FILE         Write to FILE instead of stdout"
+//usage:     "\n       bs=N            Read and write N bytes at a time"
+//usage:       IF_FEATURE_DD_IBS_OBS(
+//usage:     "\n       ibs=N           Read N bytes at a time"
+//usage:       )
+//usage:       IF_FEATURE_DD_IBS_OBS(
+//usage:     "\n       obs=N           Write N bytes at a time"
+//usage:       )
+//usage:     "\n       count=N         Copy only N input blocks"
+//usage:     "\n       skip=N          Skip N input blocks"
+//usage:     "\n       seek=N          Skip N output blocks"
+//usage:       IF_FEATURE_DD_IBS_OBS(
+//usage:     "\n       conv=notrunc    Don't truncate output file"
+//usage:     "\n       conv=noerror    Continue after read errors"
+//usage:     "\n       conv=sync       Pad blocks with zeros"
+//usage:     "\n       conv=fsync      Physically write data out before finishing"
+//usage:     "\n       conv=swab       Swap every pair of bytes"
+//usage:     "\n       iflag=skip_bytes        skip=N is in bytes"
+//usage:     "\n       iflag=fullblock Read full blocks"
+//usage:     "\n       oflag=seek_bytes        seek=N is in bytes"
+//usage:     "\n       oflag=append    Open output file in append mode"
+//usage:       )
+//usage:       IF_FEATURE_DD_STATUS(
+//usage:     "\n       status=noxfer   Suppress rate output"
+//usage:     "\n       status=none     Suppress all output"
+//usage:       )
+//usage:     "\n"
+//usage:     "\nN may be suffixed by c (1), w (2), b (512), kB (1000), k (1024), MB, M, GB, G"
+//usage:
+//usage:#define dd_example_usage
+//usage:       "$ dd if=/dev/zero of=/dev/ram1 bs=1M count=4\n"
+//usage:       "4+0 records in\n"
+//usage:       "4+0 records out\n"
 
-#include <signal.h>  /* For FEATURE_DD_SIGNAL_HANDLING */
 #include "libbb.h"
+#include "common_bufsiz.h"
 
 /* This is a NOEXEC applet. Be very careful! */
 
 
-static const struct suffix_mult dd_suffixes[] = {
-       { "c", 1 },
-       { "w", 2 },
-       { "b", 512 },
-       { "kD", 1000 },
-       { "k", 1024 },
-       { "K", 1024 },  /* compat with coreutils dd */
-       { "MD", 1000000 },
-       { "M", 1048576 },
-       { "GD", 1000000000 },
-       { "G", 1073741824 },
-       { }
+enum {
+       ifd = STDIN_FILENO,
+       ofd = STDOUT_FILENO,
 };
 
 struct globals {
        off_t out_full, out_part, in_full, in_part;
-};
-#define G (*(struct globals*)&bb_common_bufsiz1)
-/* We have to zero it out because of NOEXEC */
-#define INIT_G() memset(&G, 0, sizeof(G))
+#if ENABLE_FEATURE_DD_THIRD_STATUS_LINE
+       unsigned long long total_bytes;
+       unsigned long long begin_time_us;
+#endif
+       int flags;
+} FIX_ALIASING;
+#define G (*(struct globals*)bb_common_bufsiz1)
+#define INIT_G() do { \
+       setup_common_bufsiz(); \
+       /* we have to zero it out because of NOEXEC */ \
+       memset(&G, 0, sizeof(G)); \
+} while (0)
 
+enum {
+       /* Must be in the same order as OP_conv_XXX! */
+       /* (see "flags |= (1 << what)" below) */
+       FLAG_NOTRUNC = (1 << 0) * ENABLE_FEATURE_DD_IBS_OBS,
+       FLAG_SYNC    = (1 << 1) * ENABLE_FEATURE_DD_IBS_OBS,
+       FLAG_NOERROR = (1 << 2) * ENABLE_FEATURE_DD_IBS_OBS,
+       FLAG_FSYNC   = (1 << 3) * ENABLE_FEATURE_DD_IBS_OBS,
+       FLAG_SWAB    = (1 << 4) * ENABLE_FEATURE_DD_IBS_OBS,
+       /* end of conv flags */
+       /* start of input flags */
+       FLAG_IFLAG_SHIFT = 5,
+       FLAG_SKIP_BYTES = (1 << 5) * ENABLE_FEATURE_DD_IBS_OBS,
+       FLAG_FULLBLOCK = (1 << 6) * ENABLE_FEATURE_DD_IBS_OBS,
+       /* end of input flags */
+       /* start of output flags */
+       FLAG_OFLAG_SHIFT = 7,
+       FLAG_SEEK_BYTES = (1 << 7) * ENABLE_FEATURE_DD_IBS_OBS,
+       FLAG_APPEND = (1 << 8) * ENABLE_FEATURE_DD_IBS_OBS,
+       /* end of output flags */
+       FLAG_TWOBUFS = (1 << 9) * ENABLE_FEATURE_DD_IBS_OBS,
+       FLAG_COUNT   = 1 << 10,
+       FLAG_STATUS_NONE = 1 << 11,
+       FLAG_STATUS_NOXFER = 1 << 12,
+};
 
-static void dd_output_status(int ATTRIBUTE_UNUSED cur_signal)
+static void dd_output_status(int UNUSED_PARAM cur_signal)
 {
+#if ENABLE_FEATURE_DD_THIRD_STATUS_LINE
+       double seconds;
+       unsigned long long bytes_sec;
+       unsigned long long now_us = monotonic_us(); /* before fprintf */
+#endif
+
        /* Deliberately using %u, not %d */
        fprintf(stderr, "%"OFF_FMT"u+%"OFF_FMT"u records in\n"
                        "%"OFF_FMT"u+%"OFF_FMT"u records out\n",
                        G.in_full, G.in_part,
                        G.out_full, G.out_part);
-}
 
-static ssize_t full_write_or_warn(int fd, const void *buf, size_t len,
-       const char *const filename)
-{
-       ssize_t n = full_write(fd, buf, len);
-       if (n < 0)
-               bb_perror_msg("writing '%s'", filename);
-       return n;
+#if ENABLE_FEATURE_DD_THIRD_STATUS_LINE
+# if ENABLE_FEATURE_DD_STATUS
+       if (G.flags & FLAG_STATUS_NOXFER) /* status=noxfer active? */
+               return;
+       //TODO: should status=none make dd stop reacting to USR1 entirely?
+       //So far we react to it (we print the stats),
+       //status=none only suppresses final, non-USR1 generated status message.
+# endif
+       fprintf(stderr, "%llu bytes (%sB) copied, ",
+                       G.total_bytes,
+                       /* show fractional digit, use suffixes */
+                       make_human_readable_str(G.total_bytes, 1, 0)
+       );
+       /* Corner cases:
+        * ./busybox dd </dev/null >/dev/null
+        * ./busybox dd bs=1M count=2000 </dev/zero >/dev/null
+        * (echo DONE) | ./busybox dd >/dev/null
+        * (sleep 1; echo DONE) | ./busybox dd >/dev/null
+        */
+       seconds = (now_us - G.begin_time_us) / 1000000.0;
+       bytes_sec = G.total_bytes / seconds;
+       fprintf(stderr, "%f seconds, %sB/s\n",
+                       seconds,
+                       /* show fractional digit, use suffixes */
+                       make_human_readable_str(bytes_sec, 1, 0)
+       );
+#endif
 }
 
-static bool write_and_stats(int fd, const void *buf, size_t len, size_t obs,
+static bool write_and_stats(const void *buf, size_t len, size_t obs,
        const char *filename)
 {
-       ssize_t n = full_write_or_warn(fd, buf, len, filename);
-       if (n < 0)
-               return 1;
-       if (n == obs)
+       ssize_t n;
+
+       n = full_write(ofd, buf, len);
+#if ENABLE_FEATURE_DD_THIRD_STATUS_LINE
+       if (n > 0)
+               G.total_bytes += n;
+#endif
+       if ((size_t)n == obs) {
                G.out_full++;
-       else if (n) /* > 0 */
+               return 0;
+       }
+       if ((size_t)n == len) {
                G.out_part++;
-       return 0;
+               return 0;
+       }
+       /* n is < len (and possibly is -1).
+        * Even if n >= 0, errno is usually set correctly.
+        * For example, if writing to block device and getting ENOSPC,
+        * full_write() first sees a short write, then tries to write
+        * the remainder and gets errno set to ENOSPC.
+        * It returns n > 0 (the amount which it did write).
+        */
+       bb_perror_msg("error writing '%s'", filename);
+       return 1;
 }
 
 #if ENABLE_LFS
-#define XATOU_SFX xatoull_sfx
+# define XATOU_SFX xatoull_sfx
 #else
-#define XATOU_SFX xatoul_sfx
+# define XATOU_SFX xatoul_sfx
+#endif
+
+#if ENABLE_FEATURE_DD_IBS_OBS
+static int parse_comma_flags(char *val, const char *words, const char *error_in)
+{
+       int flags = 0;
+       while (1) {
+               int n;
+               char *arg;
+               /* find ',', replace them with NUL so we can use val for
+                * index_in_strings() without copying.
+                * We rely on val being non-null, else strchr would fault.
+                */
+               arg = strchr(val, ',');
+               if (arg)
+                       *arg = '\0';
+               n = index_in_strings(words, val);
+               if (n < 0)
+                       bb_error_msg_and_die(bb_msg_invalid_arg_to, val, error_in);
+               flags |= (1 << n);
+               if (!arg) /* no ',' left, so this was the last specifier */
+                       break;
+               *arg = ','; /* to preserve ps listing */
+               val = arg + 1; /* skip this keyword and ',' */
+       }
+       return flags;
+}
 #endif
 
 int dd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
-int dd_main(int argc, char **argv)
+int dd_main(int argc UNUSED_PARAM, char **argv)
 {
-       enum {
-               FLAG_SYNC    = 1 << 0,
-               FLAG_NOERROR = 1 << 1,
-               FLAG_NOTRUNC = 1 << 2,
-               FLAG_TWOBUFS = 1 << 3,
-               FLAG_COUNT   = 1 << 4,
-       };
        static const char keywords[] ALIGN1 =
-               "bs=\0""count=\0""seek=\0""skip=\0""if=\0""of=\0"
+               "bs\0""count\0""seek\0""skip\0""if\0""of\0"IF_FEATURE_DD_STATUS("status\0")
 #if ENABLE_FEATURE_DD_IBS_OBS
-               "ibs=\0""obs=\0""conv=\0""notrunc\0""sync\0""noerror\0"
+               "ibs\0""obs\0""conv\0""iflag\0""oflag\0"
 #endif
                ;
+#if ENABLE_FEATURE_DD_IBS_OBS
+       static const char conv_words[] ALIGN1 =
+               "notrunc\0""sync\0""noerror\0""fsync\0""swab\0";
+       static const char iflag_words[] ALIGN1 =
+               "skip_bytes\0""fullblock\0";
+       static const char oflag_words[] ALIGN1 =
+               "seek_bytes\0append\0";
+#endif
+#if ENABLE_FEATURE_DD_STATUS
+       static const char status_words[] ALIGN1 =
+               "none\0""noxfer\0";
+#endif
        enum {
-               OP_bs = 1,
+               OP_bs = 0,
                OP_count,
                OP_seek,
                OP_skip,
                OP_if,
                OP_of,
+               IF_FEATURE_DD_STATUS(OP_status,)
 #if ENABLE_FEATURE_DD_IBS_OBS
                OP_ibs,
                OP_obs,
                OP_conv,
-               OP_conv_notrunc,
+               OP_iflag,
+               OP_oflag,
+               /* Must be in the same order as FLAG_XXX! */
+               OP_conv_notrunc = 0,
                OP_conv_sync,
                OP_conv_noerror,
+               OP_conv_fsync,
+               OP_conv_swab,
+       /* Unimplemented conv=XXX: */
+       //nocreat       do not create the output file
+       //excl          fail if the output file already exists
+       //fdatasync     physically write output file data before finishing
+       //lcase         change upper case to lower case
+       //ucase         change lower case to upper case
+       //block         pad newline-terminated records with spaces to cbs-size
+       //unblock       replace trailing spaces in cbs-size records with newline
+       //ascii         from EBCDIC to ASCII
+       //ebcdic        from ASCII to EBCDIC
+       //ibm           from ASCII to alternate EBCDIC
+       /* Partially implemented: */
+       //swab          swap every pair of input bytes: will abort on non-even reads
+               OP_iflag_skip_bytes,
+               OP_iflag_fullblock,
+               OP_oflag_seek_bytes,
 #endif
        };
-       size_t ibs = 512, obs = 512;
-       ssize_t n, w;
-       char *ibuf, *obuf;
-       /* And these are all zeroed at once! */
+       smallint exitcode = EXIT_FAILURE;
+       int i;
+       size_t ibs = 512;
+       char *ibuf;
+#if ENABLE_FEATURE_DD_IBS_OBS
+       size_t obs = 512;
+       char *obuf;
+#else
+# define obs  ibs
+# define obuf ibuf
+#endif
+       /* These are all zeroed at once! */
        struct {
-               int flags;
-               int ifd, ofd;
-               size_t oc;
+               IF_FEATURE_DD_IBS_OBS(size_t ocount;)
+               ssize_t prev_read_size; /* for detecting swab failure */
                off_t count;
                off_t seek, skip;
                const char *infile, *outfile;
-#if ENABLE_FEATURE_DD_SIGNAL_HANDLING
-               struct sigaction sigact;
-#endif
        } Z;
-#define flags   (Z.flags  )
-#define ifd     (Z.ifd    )
-#define ofd     (Z.ofd    )
-#define oc      (Z.oc     )
+#define ocount  (Z.ocount )
+#define prev_read_size (Z.prev_read_size)
 #define count   (Z.count  )
 #define seek    (Z.seek   )
 #define skip    (Z.skip   )
 #define infile  (Z.infile )
 #define outfile (Z.outfile)
-#define sigact  (Z.sigact )
 
        memset(&Z, 0, sizeof(Z));
        INIT_G();
+       //fflush_all(); - is this needed because of NOEXEC?
 
-#if ENABLE_FEATURE_DD_SIGNAL_HANDLING
-       sigact.sa_handler = dd_output_status;
-       sigact.sa_flags = SA_RESTART;
-       sigemptyset(&sigact.sa_mask);
-       sigaction(SIGUSR1, &sigact, NULL);
-#endif
-
-       for (n = 1; n < argc; n++) {
-               smalluint key_len;
-               smalluint what;
-               char *key;
-               char *arg = argv[n];
+       for (i = 1; argv[i]; i++) {
+               int what;
+               char *val;
+               char *arg = argv[i];
 
-//XXX:FIXME: we reject plain "dd --" This would cost ~20 bytes, so..
-//if (*arg == '-' && *++arg == '-' && !*++arg) continue;
-               key = strstr(arg, "=");
-               if (key == NULL)
+#if ENABLE_DESKTOP
+               /* "dd --". NB: coreutils 6.9 will complain if they see
+                * more than one of them. We wouldn't. */
+               if (arg[0] == '-' && arg[1] == '-' && arg[2] == '\0')
+                       continue;
+#endif
+               val = strchr(arg, '=');
+               if (val == NULL)
                        bb_show_usage();
-               key_len = key - arg + 1;
-               key = xstrndup(arg, key_len);
-               what = index_in_strings(keywords, key) + 1;
-               if (ENABLE_FEATURE_CLEAN_UP)
-                       free(key);
-               if (what == 0)
+               *val = '\0';
+               what = index_in_strings(keywords, arg);
+               if (what < 0)
                        bb_show_usage();
-               arg += key_len;
-               /* Must fit into positive ssize_t */
+               /* *val = '='; - to preserve ps listing? */
+               val++;
 #if ENABLE_FEATURE_DD_IBS_OBS
-                       if (what == OP_ibs) {
-                               ibs = xatoul_range_sfx(arg, 1, ((size_t)-1L)/2, dd_suffixes);
-                               continue;
-                       }
-                       if (what == OP_obs) {
-                               obs = xatoul_range_sfx(arg, 1, ((size_t)-1L)/2, dd_suffixes);
-                               continue;
-                       }
-                       if (what == OP_conv) {
-                               while (1) {
-                                       /* find ',', replace them with nil so we can use arg for
-                                        * index_in_strings() without copying.
-                                        * We rely on arg being non-null, else strchr would fault.
-                                        */
-                                       key = strchr(arg, ',');
-                                       if (key)
-                                               *key = '\0';
-                                       what = index_in_strings(keywords, arg) + 1;
-                                       if (what < OP_conv_notrunc)
-                                               bb_error_msg_and_die(bb_msg_invalid_arg, arg, "conv");
-                                       if (what == OP_conv_notrunc)
-                                               flags |= FLAG_NOTRUNC;
-                                       if (what == OP_conv_sync)
-                                               flags |= FLAG_SYNC;
-                                       if (what == OP_conv_noerror)
-                                               flags |= FLAG_NOERROR;
-                                       if (!key) /* no ',' left, so this was the last specifier */
-                                               break;
-                                       arg = key + 1; /* skip this keyword and ',' */
-                               }
-                               continue;
-                       }
+               if (what == OP_ibs) {
+                       /* Must fit into positive ssize_t */
+                       ibs = xatoul_range_sfx(val, 1, ((size_t)-1L)/2, cwbkMG_suffixes);
+                       /*continue;*/
+               }
+               if (what == OP_obs) {
+                       obs = xatoul_range_sfx(val, 1, ((size_t)-1L)/2, cwbkMG_suffixes);
+                       /*continue;*/
+               }
+               if (what == OP_conv) {
+                       G.flags |= parse_comma_flags(val, conv_words, "conv");
+                       /*continue;*/
+               }
+               if (what == OP_iflag) {
+                       G.flags |= parse_comma_flags(val, iflag_words, "iflag") << FLAG_IFLAG_SHIFT;
+                       /*continue;*/
+               }
+               if (what == OP_oflag) {
+                       G.flags |= parse_comma_flags(val, oflag_words, "oflag") << FLAG_OFLAG_SHIFT;
+                       /*continue;*/
+               }
 #endif
                if (what == OP_bs) {
-                       ibs = obs = xatoul_range_sfx(arg, 1, ((size_t)-1L)/2, dd_suffixes);
-                       continue;
+                       ibs = xatoul_range_sfx(val, 1, ((size_t)-1L)/2, cwbkMG_suffixes);
+                       obs = ibs;
+                       /*continue;*/
                }
                /* These can be large: */
                if (what == OP_count) {
-                       flags |= FLAG_COUNT;
-                       count = XATOU_SFX(arg, dd_suffixes);
-                       continue;
+                       G.flags |= FLAG_COUNT;
+                       count = XATOU_SFX(val, cwbkMG_suffixes);
+                       /*continue;*/
                }
                if (what == OP_seek) {
-                       seek = XATOU_SFX(arg, dd_suffixes);
-                       continue;
+                       seek = XATOU_SFX(val, cwbkMG_suffixes);
+                       /*continue;*/
                }
                if (what == OP_skip) {
-                       skip = XATOU_SFX(arg, dd_suffixes);
-                       continue;
+                       skip = XATOU_SFX(val, cwbkMG_suffixes);
+                       /*continue;*/
                }
                if (what == OP_if) {
-                       infile = arg;
-                       continue;
+                       infile = val;
+                       /*continue;*/
                }
-               if (what == OP_of)
-                       outfile = arg;
-       }
+               if (what == OP_of) {
+                       outfile = val;
+                       /*continue;*/
+               }
+#if ENABLE_FEATURE_DD_STATUS
+               if (what == OP_status) {
+                       int n;
+                       n = index_in_strings(status_words, val);
+                       if (n < 0)
+                               bb_error_msg_and_die(bb_msg_invalid_arg_to, val, "status");
+                       G.flags |= FLAG_STATUS_NONE << n;
+                       /*continue;*/
+               }
+#endif
+       } /* end of "for (argv[i])" */
+
 //XXX:FIXME for huge ibs or obs, malloc'ing them isn't the brightest idea ever
-       ibuf = obuf = xmalloc(ibs);
+       ibuf = xmalloc(ibs);
+       obuf = ibuf;
+#if ENABLE_FEATURE_DD_IBS_OBS
        if (ibs != obs) {
-               flags |= FLAG_TWOBUFS;
+               G.flags |= FLAG_TWOBUFS;
                obuf = xmalloc(obs);
        }
-       if (infile != NULL)
-               ifd = xopen(infile, O_RDONLY);
-       else {
-               /* ifd = STDIN_FILENO; - it's zero and it's already there */
+#endif
+
+#if ENABLE_FEATURE_DD_SIGNAL_HANDLING
+       signal_SA_RESTART_empty_mask(SIGUSR1, dd_output_status);
+#endif
+#if ENABLE_FEATURE_DD_THIRD_STATUS_LINE
+       G.begin_time_us = monotonic_us();
+#endif
+
+       if (infile) {
+               xmove_fd(xopen(infile, O_RDONLY), ifd);
+       } else {
                infile = bb_msg_standard_input;
        }
-       if (outfile != NULL) {
+       if (outfile) {
                int oflag = O_WRONLY | O_CREAT;
 
-               if (!seek && !(flags & FLAG_NOTRUNC))
+               if (!seek && !(G.flags & FLAG_NOTRUNC))
                        oflag |= O_TRUNC;
+               if (G.flags & FLAG_APPEND)
+                       oflag |= O_APPEND;
 
-               ofd = xopen(outfile, oflag);
+               xmove_fd(xopen(outfile, oflag), ofd);
 
-               if (seek && !(flags & FLAG_NOTRUNC)) {
-                       if (ftruncate(ofd, seek * obs) < 0) {
+               if (seek && !(G.flags & FLAG_NOTRUNC)) {
+                       size_t blocksz = (G.flags & FLAG_SEEK_BYTES) ? 1 : obs;
+                       if (ftruncate(ofd, seek * blocksz) < 0) {
                                struct stat st;
 
-                               if (fstat(ofd, &st) < 0 || S_ISREG(st.st_mode) ||
-                                               S_ISDIR(st.st_mode))
+                               if (fstat(ofd, &st) < 0
+                                || S_ISREG(st.st_mode)
+                                || S_ISDIR(st.st_mode)
+                               ) {
                                        goto die_outfile;
+                               }
                        }
                }
        } else {
-               ofd = STDOUT_FILENO;
                outfile = bb_msg_standard_output;
        }
        if (skip) {
-               if (lseek(ifd, skip * ibs, SEEK_CUR) < 0) {
-                       while (skip-- > 0) {
-                               n = safe_read(ifd, ibuf, ibs);
+               size_t blocksz = (G.flags & FLAG_SKIP_BYTES) ? 1 : ibs;
+               if (lseek(ifd, skip * blocksz, SEEK_CUR) < 0) {
+                       do {
+                               ssize_t n;
+#if ENABLE_FEATURE_DD_IBS_OBS
+                               if (G.flags & FLAG_FULLBLOCK)
+                                       n = full_read(ifd, ibuf, blocksz);
+                               else
+#endif
+                                       n = safe_read(ifd, ibuf, blocksz);
                                if (n < 0)
                                        goto die_infile;
                                if (n == 0)
                                        break;
-                       }
+                       } while (--skip != 0);
                }
        }
        if (seek) {
-               if (lseek(ofd, seek * obs, SEEK_CUR) < 0)
+               size_t blocksz = (G.flags & FLAG_SEEK_BYTES) ? 1 : obs;
+               if (lseek(ofd, seek * blocksz, SEEK_CUR) < 0)
                        goto die_outfile;
        }
 
-       while (!(flags & FLAG_COUNT) || (G.in_full + G.in_part != count)) {
-               if (flags & FLAG_NOERROR) /* Pre-zero the buffer if conv=noerror */
-                       memset(ibuf, 0, ibs);
-               n = safe_read(ifd, ibuf, ibs);
+       while (!(G.flags & FLAG_COUNT) || (G.in_full + G.in_part != count)) {
+               ssize_t n;
+#if ENABLE_FEATURE_DD_IBS_OBS
+               if (G.flags & FLAG_FULLBLOCK)
+                       n = full_read(ifd, ibuf, ibs);
+               else
+#endif
+                       n = safe_read(ifd, ibuf, ibs);
                if (n == 0)
                        break;
                if (n < 0) {
-                       if (flags & FLAG_NOERROR) {
-                               n = ibs;
-                               bb_simple_perror_msg(infile);
-                       } else
+                       /* "Bad block" */
+                       if (!(G.flags & FLAG_NOERROR))
                                goto die_infile;
+                       bb_simple_perror_msg(infile);
+                       /* GNU dd with conv=noerror skips over bad blocks */
+                       xlseek(ifd, ibs, SEEK_CUR);
+                       /* conv=noerror,sync writes NULs,
+                        * conv=noerror just ignores input bad blocks */
+                       n = 0;
+               }
+               if (G.flags & FLAG_SWAB) {
+                       uint16_t *p16;
+                       ssize_t n2;
+
+                       /* Our code allows only last read to be odd-sized */
+                       if (prev_read_size & 1)
+                               bb_error_msg_and_die("can't swab %lu byte buffer",
+                                               (unsigned long)prev_read_size);
+                       prev_read_size = n;
+
+                       /* If n is odd, last byte is not swapped:
+                        *  echo -n "qwe" | dd conv=swab
+                        * prints "wqe".
+                        */
+                       p16 = (void*) ibuf;
+                       n2 = (n >> 1);
+                       while (--n2 >= 0) {
+                               *p16 = bswap_16(*p16);
+                               p16++;
+                       }
                }
                if ((size_t)n == ibs)
                        G.in_full++;
                else {
                        G.in_part++;
-                       if (flags & FLAG_SYNC) {
-                               memset(ibuf + n, '\0', ibs - n);
+                       if (G.flags & FLAG_SYNC) {
+                               memset(ibuf + n, 0, ibs - n);
                                n = ibs;
                        }
                }
-               if (flags & FLAG_TWOBUFS) {
+#if ENABLE_FEATURE_DD_IBS_OBS
+               if (G.flags & FLAG_TWOBUFS) {
                        char *tmp = ibuf;
                        while (n) {
-                               size_t d = obs - oc;
-
-                               if (d > n)
+                               size_t d = obs - ocount;
+                               if (d > (size_t)n)
                                        d = n;
-                               memcpy(obuf + oc, tmp, d);
+                               memcpy(obuf + ocount, tmp, d);
                                n -= d;
                                tmp += d;
-                               oc += d;
-                               if (oc == obs) {
-                                       if (write_and_stats(ofd, obuf, obs, obs, outfile))
+                               ocount += d;
+                               if (ocount == obs) {
+                                       if (write_and_stats(obuf, obs, obs, outfile))
                                                goto out_status;
-                                       oc = 0;
+                                       ocount = 0;
                                }
                        }
-               } else if (write_and_stats(ofd, ibuf, n, obs, outfile))
-                       goto out_status;
+               } else
+#endif
+               {
+                       if (write_and_stats(ibuf, n, obs, outfile))
+                               goto out_status;
+               }
        }
 
-       if (ENABLE_FEATURE_DD_IBS_OBS && oc) {
-               w = full_write_or_warn(ofd, obuf, oc, outfile);
-               if (w < 0) goto out_status;
-               if (w > 0)
-                       G.out_part++;
+       if (G.flags & FLAG_FSYNC) {
+               if (fsync(ofd) < 0)
+                       goto die_outfile;
        }
+
+#if ENABLE_FEATURE_DD_IBS_OBS
+       if (ocount != 0) {
+               if (write_and_stats(obuf, ocount, obs, outfile))
+                       goto out_status;
+       }
+#endif
        if (close(ifd) < 0) {
  die_infile:
                bb_simple_perror_msg_and_die(infile);
@@ -327,8 +594,17 @@ int dd_main(int argc, char **argv)
  die_outfile:
                bb_simple_perror_msg_and_die(outfile);
        }
+
+       exitcode = EXIT_SUCCESS;
  out_status:
-       dd_output_status(0);
+       if (!ENABLE_FEATURE_DD_STATUS || !(G.flags & FLAG_STATUS_NONE))
+               dd_output_status(0);
+
+       if (ENABLE_FEATURE_CLEAN_UP) {
+               free(obuf);
+               if (G.flags & FLAG_TWOBUFS)
+                       free(ibuf);
+       }
 
-       return EXIT_SUCCESS;
+       return exitcode;
 }