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dd: add count_bytes, skip_bytes and seek_bytes flags
dd now accepts the count_bytes and skip_bytes input flag and the seek_bytes output flag, to more easily allow processing portions of a file. * src/dd.c (scanargs): Compute skip_records and skip_bytes when 'skip_bytes' iflag is used. Compute max_records and max_bytes when 'count_bytes' iflag is used. Compute seek_records and seek_bytes when 'seek_bytes' oflag is used. (skip_via_lseek): Use new 'bytes' parameter and handle potential 'records' equals to zero. Update the bytes parameter when called with 'fdesc' equal to STDOUT_FILENO. Update the header comments. (dd_copy): Skip accordingly to skip_records AND skip_bytes. Count accordingly to max_records AND max_bytes. Seek on output accordingly to seek_records AND seek_bytes. * NEWS (New features): Mention it. * doc/coreutils.texi (dd invocation): Detail new flags and behaviors. * tests/dd/bytes: New file. Tests for these new flags. * tests/Makefile.am (TESTS): Add it.
This commit is contained in:
Jérémy Compostella
Pádraig Brady
parent
da2b32e7af
commit
140eca15c4
5
NEWS
5
NEWS
@ -2,6 +2,11 @@ GNU coreutils NEWS -*- outline -*-
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* Noteworthy changes in release ?.? (????-??-??) [?]
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** New features
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dd now accepts the count_bytes, skip_bytes iflags and the count_bytes
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oflag, to more easily allow processing portions of a file.
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** Bug fixes
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mv now lets you move a symlink onto a same-inode destination file that
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@ -8057,18 +8057,24 @@ When converting variable-length records to fixed-length ones
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(@option{conv=block}) or the reverse (@option{conv=unblock}),
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use @var{bytes} as the fixed record length.
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@item skip=@var{blocks}
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@item skip=@var{n}
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@opindex skip
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Skip @var{blocks} @samp{ibs}-byte blocks in the input file before copying.
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Skip @var{n} @samp{ibs}-byte blocks in the input file before copying.
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If @samp{iflag=skip_bytes} is specified, @var{n} is interpreted
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as a byte count rather than a block count.
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@item seek=@var{blocks}
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@item seek=@var{n}
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@opindex seek
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Skip @var{blocks} @samp{obs}-byte blocks in the output file before copying.
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Skip @var{n} @samp{obs}-byte blocks in the output file before copying.
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if @samp{oflag=seek_bytes} is specified, @var{n} is interpreted
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as a byte count rather than a block count.
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@item count=@var{blocks}
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@item count=@var{n}
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@opindex count
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Copy @var{blocks} @samp{ibs}-byte blocks from the input file, instead
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Copy @var{n} @samp{ibs}-byte blocks from the input file, instead
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of everything until the end of the file.
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if @samp{iflag=count_bytes} is specified, @var{n} is interpreted
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as a byte count rather than a block count.
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@item status=noxfer
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@opindex status
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@ -8321,6 +8327,27 @@ When that happens, continue calling @code{read} to fill the remainder
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of the block.
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This flag can be used only with @code{iflag}.
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@item count_bytes
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@opindex count_bytes
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Interpret the @samp{count=} operand as a byte count,
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rather than a block count, which allows specifying
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a length that is not a multiple of the I/O block size.
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This flag can be used only with @code{iflag}.
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@item skip_bytes
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@opindex skip_bytes
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Interpret the @samp{skip=} operand as a byte count,
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rather than a block count, which allows specifying
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an offset that is not a multiple of the I/O block size.
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This flag can be used only with @code{iflag}.
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@item seek_bytes
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@opindex seek_bytes
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Interpret the @samp{seek=} operand as a byte count,
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rather than a block count, which allows specifying
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an offset that is not a multiple of the I/O block size.
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This flag can be used only with @code{oflag}.
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@end table
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These flags are not supported on all systems, and @samp{dd} rejects
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@ -8343,10 +8370,13 @@ should not be too large---values larger than a few megabytes
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are generally wasteful or (as in the gigabyte..exabyte case) downright
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counterproductive or error-inducing.
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Use different @command{dd} invocations to use different block sizes for
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skipping and I/O@. For example, the following shell commands copy data
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in 512 KiB blocks between a disk and a tape, but do not save or restore a
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4 KiB label at the start of the disk:
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To process data that is at an offset or size that is not a
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multiple of the I/O@ block size, you can use the @samp{skip_bytes},
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@samp{seek_bytes} and @samp{count_bytes} flags. Alternatively
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the traditional method of separate @command{dd} invocations can be used.
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For example, the following shell commands copy data
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in 512 KiB blocks between a disk and a tape, but do not save
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or restore a 4 KiB label at the start of the disk:
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@example
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disk=/dev/rdsk/c0t1d0s2
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204
src/dd.c
204
src/dd.c
@ -156,12 +156,23 @@ static size_t conversion_blocksize = 0;
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/* Skip this many records of 'input_blocksize' bytes before input. */
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static uintmax_t skip_records = 0;
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/* Skip this many bytes before input in addition of 'skip_records'
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records. */
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static size_t skip_bytes = 0;
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/* Skip this many records of 'output_blocksize' bytes before output. */
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static uintmax_t seek_records = 0;
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/* Skip this many bytes in addition to 'seek_records' records before
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output. */
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static uintmax_t seek_bytes = 0;
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/* Copy only this many records. The default is effectively infinity. */
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static uintmax_t max_records = (uintmax_t) -1;
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/* Copy this many bytes in addition to 'max_records' records. */
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static size_t max_bytes = 0;
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/* Bit vector of conversions to apply. */
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static int conversions_mask = 0;
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@ -241,7 +252,7 @@ static bool i_nocache, o_nocache;
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static ssize_t (*iread_fnc) (int fd, char *buf, size_t size);
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/* A longest symbol in the struct symbol_values tables below. */
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#define LONGEST_SYMBOL "fdatasync"
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#define LONGEST_SYMBOL "count_bytes"
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/* A symbol and the corresponding integer value. */
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struct symbol_value
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@ -296,37 +307,55 @@ enum
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O_FULLBLOCK = FFS_MASK (v),
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v2 = v ^ O_FULLBLOCK,
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O_NOCACHE = FFS_MASK (v2)
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O_NOCACHE = FFS_MASK (v2),
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v3 = v2 ^ O_NOCACHE,
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O_COUNT_BYTES = FFS_MASK (v3),
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v4 = v3 ^ O_COUNT_BYTES,
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O_SKIP_BYTES = FFS_MASK (v4),
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v5 = v4 ^ O_SKIP_BYTES,
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O_SEEK_BYTES = FFS_MASK (v5)
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};
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/* Ensure that we got something. */
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verify (O_FULLBLOCK != 0);
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verify (O_NOCACHE != 0);
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verify (O_COUNT_BYTES != 0);
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verify (O_SKIP_BYTES != 0);
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verify (O_SEEK_BYTES != 0);
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#define MULTIPLE_BITS_SET(i) (((i) & ((i) - 1)) != 0)
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/* Ensure that this is a single-bit value. */
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verify ( ! MULTIPLE_BITS_SET (O_FULLBLOCK));
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verify ( ! MULTIPLE_BITS_SET (O_NOCACHE));
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verify ( ! MULTIPLE_BITS_SET (O_COUNT_BYTES));
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verify ( ! MULTIPLE_BITS_SET (O_SKIP_BYTES));
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verify ( ! MULTIPLE_BITS_SET (O_SEEK_BYTES));
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/* Flags, for iflag="..." and oflag="...". */
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static struct symbol_value const flags[] =
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{
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{"append", O_APPEND},
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{"binary", O_BINARY},
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{"cio", O_CIO},
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{"direct", O_DIRECT},
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{"directory", O_DIRECTORY},
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{"dsync", O_DSYNC},
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{"noatime", O_NOATIME},
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{"nocache", O_NOCACHE}, /* Discard cache. */
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{"noctty", O_NOCTTY},
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{"nofollow", HAVE_WORKING_O_NOFOLLOW ? O_NOFOLLOW : 0},
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{"nolinks", O_NOLINKS},
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{"nonblock", O_NONBLOCK},
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{"sync", O_SYNC},
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{"text", O_TEXT},
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{"fullblock", O_FULLBLOCK}, /* Accumulate full blocks from input. */
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{"append", O_APPEND},
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{"binary", O_BINARY},
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{"cio", O_CIO},
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{"direct", O_DIRECT},
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{"directory", O_DIRECTORY},
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{"dsync", O_DSYNC},
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{"noatime", O_NOATIME},
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{"nocache", O_NOCACHE}, /* Discard cache. */
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{"noctty", O_NOCTTY},
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{"nofollow", HAVE_WORKING_O_NOFOLLOW ? O_NOFOLLOW : 0},
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{"nolinks", O_NOLINKS},
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{"nonblock", O_NONBLOCK},
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{"sync", O_SYNC},
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{"text", O_TEXT},
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{"fullblock", O_FULLBLOCK}, /* Accumulate full blocks from input. */
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{"count_bytes", O_COUNT_BYTES},
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{"skip_bytes", O_SKIP_BYTES},
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{"seek_bytes", O_SEEK_BYTES},
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{"", 0}
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};
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@ -489,7 +518,7 @@ Copy a file, converting and formatting according to the operands.\n\
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bs=BYTES read and write up to BYTES bytes at a time\n\
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cbs=BYTES convert BYTES bytes at a time\n\
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conv=CONVS convert the file as per the comma separated symbol list\n\
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count=BLOCKS copy only BLOCKS input blocks\n\
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count=N copy only N input blocks\n\
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ibs=BYTES read up to BYTES bytes at a time (default: 512)\n\
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"), stdout);
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fputs (_("\
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@ -498,8 +527,8 @@ Copy a file, converting and formatting according to the operands.\n\
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obs=BYTES write BYTES bytes at a time (default: 512)\n\
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of=FILE write to FILE instead of stdout\n\
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oflag=FLAGS write as per the comma separated symbol list\n\
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seek=BLOCKS skip BLOCKS obs-sized blocks at start of output\n\
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skip=BLOCKS skip BLOCKS ibs-sized blocks at start of input\n\
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seek=N skip N obs-sized blocks at start of output\n\
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skip=N skip N ibs-sized blocks at start of input\n\
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status=noxfer suppress transfer statistics\n\
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"), stdout);
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fputs (_("\
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@ -568,6 +597,15 @@ Each FLAG symbol may be:\n\
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fputs (_(" binary use binary I/O for data\n"), stdout);
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if (O_TEXT)
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fputs (_(" text use text I/O for data\n"), stdout);
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if (O_COUNT_BYTES)
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fputs (_(" count_bytes treat 'count=N' as a byte count (iflag only)\n\
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"), stdout);
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if (O_SKIP_BYTES)
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fputs (_(" skip_bytes treat 'skip=N' as a byte count (iflag only)\n\
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"), stdout);
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if (O_SEEK_BYTES)
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fputs (_(" seek_bytes treat 'seek=N' as a byte count (oflag only)\n\
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"), stdout);
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{
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char const *siginfo_name = (SIGINFO == SIGUSR1 ? "USR1" : "INFO");
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@ -1120,6 +1158,9 @@ scanargs (int argc, char *const *argv)
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{
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int i;
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size_t blocksize = 0;
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uintmax_t count = (uintmax_t) -1;
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uintmax_t skip = 0;
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uintmax_t seek = 0;
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for (i = optind; i < argc; i++)
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{
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@ -1175,11 +1216,11 @@ scanargs (int argc, char *const *argv)
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conversion_blocksize = n;
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}
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else if (operand_is (name, "skip"))
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skip_records = n;
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skip = n;
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else if (operand_is (name, "seek"))
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seek_records = n;
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seek = n;
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else if (operand_is (name, "count"))
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max_records = n;
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count = n;
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else
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{
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error (0, 0, _("unrecognized operand %s"), quote (name));
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@ -1216,6 +1257,43 @@ scanargs (int argc, char *const *argv)
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usage (EXIT_FAILURE);
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}
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if (input_flags & O_SEEK_BYTES)
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{
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error (0, 0, "%s: %s", _("invalid input flag"), "'seek_bytes'");
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usage (EXIT_FAILURE);
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}
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if (output_flags & (O_COUNT_BYTES | O_SKIP_BYTES))
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{
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error (0, 0, "%s: %s", _("invalid output flag"),
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output_flags & O_COUNT_BYTES ? "'count_bytes'" : "'skip_bytes'");
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usage (EXIT_FAILURE);
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}
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if (input_flags & O_SKIP_BYTES && skip != 0)
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{
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skip_records = skip / input_blocksize;
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skip_bytes = skip % input_blocksize;
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}
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else if (skip != 0)
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skip_records = skip;
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if (input_flags & O_COUNT_BYTES && count != (uintmax_t) -1)
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{
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max_records = count / input_blocksize;
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max_bytes = count % input_blocksize;
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}
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else if (count != (uintmax_t) -1)
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max_records = count;
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if (output_flags & O_SEEK_BYTES && seek != 0)
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{
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seek_records = seek / output_blocksize;
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seek_bytes = seek % output_blocksize;
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}
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else if (seek != 0)
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seek_records = seek;
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/* Warn about partial reads if bs=SIZE is given and iflag=fullblock
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is not, and if counting or skipping bytes or using direct I/O.
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This helps to avoid confusion with miscounts, and to avoid issues
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@ -1411,18 +1489,20 @@ skip_via_lseek (char const *filename, int fdesc, off_t offset, int whence)
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# define skip_via_lseek(Filename, Fd, Offset, Whence) lseek (Fd, Offset, Whence)
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#endif
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/* Throw away RECORDS blocks of BLOCKSIZE bytes on file descriptor FDESC,
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which is open with read permission for FILE. Store up to BLOCKSIZE
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bytes of the data at a time in BUF, if necessary. RECORDS must be
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nonzero. If fdesc is STDIN_FILENO, advance the input offset.
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Return the number of records remaining, i.e., that were not skipped
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because EOF was reached. */
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/* Throw away RECORDS blocks of BLOCKSIZE bytes plus BYTES bytes on
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file descriptor FDESC, which is open with read permission for FILE.
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Store up to BLOCKSIZE bytes of the data at a time in BUF, if
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necessary. RECORDS or BYTES must be nonzero. If FDESC is
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STDIN_FILENO, advance the input offset. Return the number of
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records remaining, i.e., that were not skipped because EOF was
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reached. If FDESC is STDOUT_FILENO, on return, BYTES is the
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remaining bytes in addition to the remaining records. */
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static uintmax_t
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skip (int fdesc, char const *file, uintmax_t records, size_t blocksize,
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char *buf)
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size_t *bytes, char *buf)
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{
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uintmax_t offset = records * blocksize;
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uintmax_t offset = records * blocksize + *bytes;
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/* Try lseek and if an error indicates it was an inappropriate operation --
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or if the file offset is not representable as an off_t --
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@ -1450,7 +1530,10 @@ skip (int fdesc, char const *file, uintmax_t records, size_t blocksize,
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advance_input_offset (offset);
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}
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else
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records = 0;
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{
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records = 0;
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*bytes = 0;
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}
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return records;
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}
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else
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@ -1491,29 +1574,30 @@ skip (int fdesc, char const *file, uintmax_t records, size_t blocksize,
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do
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{
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ssize_t nread = iread_fnc (fdesc, buf, blocksize);
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ssize_t nread = iread_fnc (fdesc, buf, records ? blocksize : *bytes);
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if (nread < 0)
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{
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if (fdesc == STDIN_FILENO)
|
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{
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error (0, errno, _("reading %s"), quote (file));
|
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if (conversions_mask & C_NOERROR)
|
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{
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print_stats ();
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continue;
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}
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print_stats ();
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}
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else
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error (0, lseek_errno, _("%s: cannot seek"), quote (file));
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quit (EXIT_FAILURE);
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}
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if (nread == 0)
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else if (nread == 0)
|
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break;
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if (fdesc == STDIN_FILENO)
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else if (fdesc == STDIN_FILENO)
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advance_input_offset (nread);
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|
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if (records != 0)
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records--;
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else
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*bytes = 0;
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}
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while (--records != 0);
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while (records || *bytes);
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return records;
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}
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@ -1777,11 +1861,13 @@ dd_copy (void)
|
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obuf = ibuf;
|
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}
|
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|
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if (skip_records != 0)
|
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if (skip_records != 0 || skip_bytes != 0)
|
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{
|
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uintmax_t us_bytes = input_offset + (skip_records * input_blocksize);
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uintmax_t us_bytes = input_offset + (skip_records * input_blocksize)
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+ skip_bytes;
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uintmax_t us_blocks = skip (STDIN_FILENO, input_file,
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skip_records, input_blocksize, ibuf);
|
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skip_records, input_blocksize, &skip_bytes,
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ibuf);
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us_bytes -= input_offset;
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|
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/* POSIX doesn't say what to do when dd detects it has been
|
||||
@ -1797,34 +1883,41 @@ dd_copy (void)
|
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}
|
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}
|
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|
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if (seek_records != 0)
|
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if (seek_records != 0 || seek_bytes != 0)
|
||||
{
|
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size_t bytes = seek_bytes;
|
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uintmax_t write_records = skip (STDOUT_FILENO, output_file,
|
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seek_records, output_blocksize, obuf);
|
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seek_records, output_blocksize, &bytes,
|
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obuf);
|
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|
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if (write_records != 0)
|
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if (write_records != 0 || bytes != 0)
|
||||
{
|
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memset (obuf, 0, output_blocksize);
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memset (obuf, 0, write_records ? output_blocksize : bytes);
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|
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do
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{
|
||||
if (iwrite (STDOUT_FILENO, obuf, output_blocksize)
|
||||
!= output_blocksize)
|
||||
size_t size = write_records ? output_blocksize : bytes;
|
||||
if (iwrite (STDOUT_FILENO, obuf, size) != size)
|
||||
{
|
||||
error (0, errno, _("writing to %s"), quote (output_file));
|
||||
quit (EXIT_FAILURE);
|
||||
}
|
||||
|
||||
if (write_records != 0)
|
||||
write_records--;
|
||||
else
|
||||
bytes = 0;
|
||||
}
|
||||
while (--write_records != 0);
|
||||
while (write_records || bytes);
|
||||
}
|
||||
}
|
||||
|
||||
if (max_records == 0)
|
||||
if (max_records == 0 && max_bytes == 0)
|
||||
return exit_status;
|
||||
|
||||
while (1)
|
||||
{
|
||||
if (r_partial + r_full >= max_records)
|
||||
if (r_partial + r_full >= max_records + (max_bytes ? 1 : 0))
|
||||
break;
|
||||
|
||||
/* Zero the buffer before reading, so that if we get a read error,
|
||||
@ -1835,7 +1928,10 @@ dd_copy (void)
|
||||
(conversions_mask & (C_BLOCK | C_UNBLOCK)) ? ' ' : '\0',
|
||||
input_blocksize);
|
||||
|
||||
nread = iread_fnc (STDIN_FILENO, ibuf, input_blocksize);
|
||||
if (r_partial + r_full >= max_records)
|
||||
nread = iread_fnc (STDIN_FILENO, ibuf, max_bytes);
|
||||
else
|
||||
nread = iread_fnc (STDIN_FILENO, ibuf, input_blocksize);
|
||||
|
||||
if (nread >= 0 && i_nocache)
|
||||
invalidate_cache (STDIN_FILENO, nread);
|
||||
|
||||
@ -369,6 +369,7 @@ TESTS = \
|
||||
dd/reblock \
|
||||
dd/skip-seek \
|
||||
dd/skip-seek2 \
|
||||
dd/bytes \
|
||||
dd/skip-seek-past-file \
|
||||
dd/stderr \
|
||||
dd/unblock \
|
||||
|
||||
57
tests/dd/bytes
Executable file
57
tests/dd/bytes
Executable file
@ -0,0 +1,57 @@
|
||||
#!/bin/sh
|
||||
|
||||
# Copyright (C) 2012 Free Software Foundation, Inc.
|
||||
|
||||
# This program is free software: you can redistribute it and/or modify
|
||||
# it under the terms of the GNU General Public License as published by
|
||||
# the Free Software Foundation, either version 3 of the License, or
|
||||
# (at your option) any later version.
|
||||
|
||||
# This program is distributed in the hope that it will be useful,
|
||||
# but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||||
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||||
# GNU General Public License for more details.
|
||||
|
||||
# You should have received a copy of the GNU General Public License
|
||||
# along with this program. If not, see <http://www.gnu.org/licenses/>.
|
||||
|
||||
. "${srcdir=.}/init.sh"; path_prepend_ ../src
|
||||
print_ver_ dd
|
||||
|
||||
# count_bytes
|
||||
echo 0123456789abcdefghijklm > in || framework_failure_
|
||||
dd count=14 conv=swab iflag=count_bytes < in > out 2> /dev/null || fail=1
|
||||
case `cat out` in
|
||||
1032547698badc) ;;
|
||||
*) fail=1 ;;
|
||||
esac
|
||||
|
||||
# skip_bytes
|
||||
echo 0123456789abcdefghijklm > in || framework_failure_
|
||||
dd skip=10 iflag=skip_bytes < in > out 2> /dev/null || fail=1
|
||||
case `cat out` in
|
||||
abcdefghijklm) ;;
|
||||
*) fail=1 ;;
|
||||
esac
|
||||
|
||||
# skip records and bytes from pipe
|
||||
echo 0123456789abcdefghijklm |
|
||||
dd skip=10 bs=2 iflag=skip_bytes > out 2> /dev/null || fail=1
|
||||
case `cat out` in
|
||||
abcdefghijklm) ;;
|
||||
*) fail=1 ;;
|
||||
esac
|
||||
|
||||
# seek bytes
|
||||
echo abcdefghijklm |
|
||||
dd bs=5 seek=8 oflag=seek_bytes > out 2> /dev/null || fail=1
|
||||
echo abcdefghijklm |
|
||||
dd bs=4 seek=2 > expected 2> /dev/null || fail=1
|
||||
compare expected out || fail=1
|
||||
|
||||
# seek bytes on empty file
|
||||
echo abcdefghijklm |
|
||||
dd bs=5 seek=8 oflag=seek_bytes > out2 2> /dev/null || fail=1
|
||||
compare expected out2 || fail=1
|
||||
|
||||
Exit $fail
|
||||
Loading…
Reference in New Issue
Block a user