Using cat, head, tail on binary files

Using cat, head, tail on binary files

[Erik Sobel]

What is the trick to getting cat, head, and tail to work correctly with 
binary files under WinNT?  I tried setting the CYGWIN environment variable 
to "binmode" as recommended by the documentation.  This got things closer 
to working but it's still not right.

Example:  given a binary file named foo of size 10000 bytes
CYGWIN=tty
head -c50 foo > foo.part1              # got 23 bytes from foo
tail -c1000 foo > foo.part2             # got 648 bytes from foo
cat foo.part1 foo.part2 > new_foo  # is not the sum of the two input file sizes

CYGWIN=binmode
head -c50 foo > foo.part1              # got 58 bytes from foo
tail -c1000 foo > foo.part2             # got 1046 bytes from foo
cat foo.part1 foo.part2 > new_foo  # is not the sum of the two input file sizes

cat foo foo > foo2  # is not twice the size of foo

Any suggestions would be appreciated.

Thanks,
Erik
----------------------------------------------------------------------------------------------------------
Erik Sobel
esobel@alphatech.com
----------------------------------------------------------------------------------------------------------


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Re: Using cat, head, tail on binary files

[Gerald Villemure]

Use the dd command to work with binary files.

For example:
dd if=foo of=foo.part1 bs=1kD count=10

This will create a file called 'foo.part1' with the first 10000 bytes

If you want part2 one way is:
dd if=foo of=foo.part2 bs=1kD skip=10

Hope this helps
Gerald

----- Original Message -----
From: "Erik Sobel" <erik.sobel@alphatech.com>
To: <cygwin@cygwin.com>
Sent: Tuesday, November 27, 2001 4:16 PM
Subject: Using cat, head, tail on binary files


> What is the trick to getting cat, head, and tail to work correctly with
> binary files under WinNT?  I tried setting the CYGWIN environment variable
> to "binmode" as recommended by the documentation.  This got things closer
> to working but it's still not right.
>
> Example:  given a binary file named foo of size 10000 bytes
> CYGWIN=tty
> head -c50 foo > foo.part1              # got 23 bytes from foo
> tail -c1000 foo > foo.part2             # got 648 bytes from foo
> cat foo.part1 foo.part2 > new_foo  # is not the sum of the two input file
sizes
>
> CYGWIN=binmode
> head -c50 foo > foo.part1              # got 58 bytes from foo
> tail -c1000 foo > foo.part2             # got 1046 bytes from foo
> cat foo.part1 foo.part2 > new_foo  # is not the sum of the two input file
sizes
>
> cat foo foo > foo2  # is not twice the size of foo
>
> Any suggestions would be appreciated.
>
> Thanks,
> Erik
> --------------------------------------------------------------------------
--------------------------------
> Erik Sobel
> esobel@alphatech.com
> --------------------------------------------------------------------------
--------------------------------



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Using cat, head, tail on binary files

[Erik Sobel]

What is the trick to getting cat, head, and tail to work correctly with 
binary files under WinNT?  I tried setting the CYGWIN environment variable 
to "binmode" as recommended by the documentation.  This got things closer 
to working but it's still not right.

Example:  given a binary file named foo of size 10000 bytes
CYGWIN=tty
head -c50 foo > foo.part1              # got 23 bytes from foo
tail -c1000 foo > foo.part2             # got 648 bytes from foo
cat foo.part1 foo.part2 > new_foo  # is not the sum of the two input file sizes

CYGWIN=binmode
head -c50 foo > foo.part1              # got 58 bytes from foo
tail -c1000 foo > foo.part2             # got 1046 bytes from foo
cat foo.part1 foo.part2 > new_foo  # is not the sum of the two input file sizes

cat foo foo > foo2  # is not twice the size of foo

Any suggestions would be appreciated.

Thanks,
Erik
----------------------------------------------------------------------------------------------------------
Erik Sobel
esobel@alphatech.com
----------------------------------------------------------------------------------------------------------


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Re: Using cat, head, tail on binary files

[Gerald Villemure]

Use the dd command to work with binary files.

For example:
dd if=foo of=foo.part1 bs=1kD count=10

This will create a file called 'foo.part1' with the first 10000 bytes

If you want part2 one way is:
dd if=foo of=foo.part2 bs=1kD skip=10

Hope this helps
Gerald

----- Original Message -----
From: "Erik Sobel" <erik.sobel@alphatech.com>
To: <cygwin@cygwin.com>
Sent: Tuesday, November 27, 2001 4:16 PM
Subject: Using cat, head, tail on binary files


> What is the trick to getting cat, head, and tail to work correctly with
> binary files under WinNT?  I tried setting the CYGWIN environment variable
> to "binmode" as recommended by the documentation.  This got things closer
> to working but it's still not right.
>
> Example:  given a binary file named foo of size 10000 bytes
> CYGWIN=tty
> head -c50 foo > foo.part1              # got 23 bytes from foo
> tail -c1000 foo > foo.part2             # got 648 bytes from foo
> cat foo.part1 foo.part2 > new_foo  # is not the sum of the two input file
sizes
>
> CYGWIN=binmode
> head -c50 foo > foo.part1              # got 58 bytes from foo
> tail -c1000 foo > foo.part2             # got 1046 bytes from foo
> cat foo.part1 foo.part2 > new_foo  # is not the sum of the two input file
sizes
>
> cat foo foo > foo2  # is not twice the size of foo
>
> Any suggestions would be appreciated.
>
> Thanks,
> Erik
> --------------------------------------------------------------------------
--------------------------------
> Erik Sobel
> esobel@alphatech.com
> --------------------------------------------------------------------------
--------------------------------



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