writing into binary file

[Sanjeev Kumar]

I am pretty new to tcl/tk, i have written below code to create a
binary file with just one byte of data in it

set fp [open test.bin w]
fconfigure $fp -translation binary -encoding binary
puts -nonewline $fp [format binary s1 [expr 0x20]]
close $fp

when I open the file in binary editing mode (using UltraEdit), i am
seeing "20 00", it is appending 00 (NULL), don't know why...what else
needs to added to make it work properly

btw i am using tcl version 8.3.4

-Sanjeev

[Les Cargill]

From http://tmml.sourceforge.net/doc/tcl/binary.html

"s
This form is the same as c except that it stores one or more 16-bit
integers in little-endian byte order in the output string. The low-order
16-bits of each integer are stored as a two-byte value at the cursor
position with the least significant byte stored first. For example,

binary format s3 {3 -3 258 1}

will return a string equivalent to \x03\x00\xfd\xff\x02\x01.
"

Emphasis "two-byte".

--
Les Cargill

[Georgios Petasis]

O/H Sanjeev Kumar έγραψε:

Why do you need format? (Which does not work as written: it puts in the
file just "binary")

George

[Sanjeev Kumar]

On Jul 9, 4:10 pm, Les Cargill <lcarg...@cfl.rr.com> wrote:
> Sanjeev Kumar wrote:
> > I am pretty new to tcl/tk, i have written below code to create a
> > binary file with just one byte of data in it
>
> > set fp [open test.bin w]
> > fconfigure $fp -translation binary -encoding binary
> > puts -nonewline $fp [format binary s1 [expr 0x20]]
> > close $fp
>
> > when I open the file in binary editing mode (using UltraEdit), i am
> > seeing "20 00", it is appending 00 (NULL), don't know why...what else
> > needs to added to make it work properly
>
> > btw i am using tcl version 8.3.4
>
> > -Sanjeev
>

>  Fromhttp://tmml.sourceforge.net/doc/tcl/binary.html

>
> "s
>      This form is the same as c except that it stores one or more 16-bit
> integers in little-endian byte order in the output string. The low-order
> 16-bits of each integer are stored as a two-byte value at the cursor
> position with the least significant byte stored first. For example,
>
>      binary format s3 {3 -3 258 1}
>
>      will return a string equivalent to \x03\x00\xfd\xff\x02\x01.
> "
>
> Emphasis "two-byte".
>
> --

> Les Cargill- Hide quoted text -
>
> - Show quoted text -

found the way replacing 's' with 'c' character works

set fp [open test.bin w]
fconfigure $fp -translation binary -encoding binary

puts -nonewline $fp [format binary c1 [expr 0x20]]
close $fp

[Pat Thoyts]

Sanjeev Kumar <sanj...@gmail.com> writes:

>set fp [open test.bin w]
>fconfigure $fp -translation binary -encoding binary
>puts -nonewline $fp [format binary s1 [expr 0x20]]

I assume you mean [binary format s ..]

You asked it to write a 2 byte signed integer (aka short). Therefore
you got a file with two bytes in little-endian byte order.

If you want a single byte - use 'c'

--
Pat Thoyts http://www.patthoyts.tk/
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