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dd.c
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dd.c
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/* Copyright (c) 2017, Piotr Durlej
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <fcntl.h>
#include <err.h>
static char * buf;
static int bs = 512;
static char * infile = NULL;
static char * outfile = NULL;
static int count = -1;
static int ifd = STDIN_FILENO;
static int ofd = STDOUT_FILENO;
static long seek = 0;
static long skip = 0;
static int do_dd(void)
{
struct stat st;
int ic = 0;
int pic = 0;
int oc = 0;
int poc = 0;
int cnt;
if (fstat(ifd, &st))
err(1, "%s: fstat", infile);
if (skip && S_ISREG(st.st_mode))
{
if (lseek(ifd, bs * skip, SEEK_SET) < 0)
err(1, "dd: %s: lseek", infile);
skip = 0;
}
if (seek && lseek(ofd, bs * seek, SEEK_SET) < 0)
err(1, "%s: lseek", outfile);
errno = 0;
while (count)
{
cnt = read(ifd, buf, bs);
if (cnt < 0)
err(1, "%s: read", infile);
if (!cnt)
{
errno = 0;
break;
}
if (cnt == bs)
ic++;
else
pic++;
if (skip)
{
skip--;
continue;
}
if (write(ofd, buf, cnt) != cnt)
err(1, "%s: write", outfile);
if (cnt == bs)
oc++;
else
poc++;
if (count != -1)
count--;
if (!count)
errno = 0;
}
fprintf(stderr, "%i+%i blocks in\n", ic, pic);
fprintf(stderr, "%i+%i blocks out\n", oc, poc);
return errno;
}
int main(int argc, char **argv)
{
int i;
if (argc == 2 && !strcmp(argv[1], "--help"))
{
printf("\nUsage: dd [if=INPUT] [of=OUTPUT] [bs=BLKSIZE] "
"[count=COUNT] [seek=BLOCKS] [skip=BLOCKS]\n\n"
"Copy blocks from INPUT to OUTPUT.\n\n"
" if=INPUT use INPUT instead of the default stdin\n"
" of=OUTPUT use OUTPUT instead of the default stdout\n"
" bs=BLKSIZE set block size to BLKSIZE (default is 512 bytes)\n"
" count=COUNT limit the number of blocks transferred to COUNT blocks\n"
" seek=BLOCKS seek on output to BLOCKS*BLKSIZE\n"
" skip=BLOCKS skip BLOCKS blocks on input\n\n"
);
return 0;
}
for (i = 1; i < argc; i++)
{
if (!strncmp("if=", argv[i], 3))
{
infile = argv[i] + 3;
continue;
}
if (!strncmp("of=", argv[i], 3))
{
outfile = argv[i] + 3;
continue;
}
if (!strncmp("bs=", argv[i], 3))
{
bs = strtoul(argv[i] + 3, NULL, 0);
continue;
}
if (!strncmp("count=", argv[i], 6))
{
count = strtoul(argv[i] + 6, NULL, 0);
continue;
}
if (!strncmp("seek=", argv[i], 5))
{
seek = strtoul(argv[i] + 5, NULL, 0);
continue;
}
if (!strncmp("skip=", argv[i], 5))
{
skip = strtoul(argv[i] + 5, NULL, 0);
continue;
}
errx(1, "invalid argument: %s", argv[i]);
}
buf = malloc(bs);
if (buf == NULL)
err(1, "malloc");
if (infile != NULL)
{
ifd = open(infile, O_RDONLY);
if (ifd < 0)
err(1, "%s: open", infile);
}
else
infile = "stdin";
if (outfile != NULL)
{
ofd = open(outfile, O_WRONLY | O_CREAT, 0666);
if (ofd < 0)
err(1, "%s: open", outfile);
}
else
outfile = "stdout";
return do_dd();
}