As bash cannot cope with a byte value of zero inside a variable then this is a workaround.
This code is a DEMO to show how to create a _string_variable_ containing all of the values of 1 to 255 as single characters and 0, (zero), as a two byte character set of \0.
The real binary files are 512 bytes in size and contains 2 zeros.
The _string_variable_ is 514 bytes in size and contains \0 for the byte value zero.
Ignore the simplicity of the for loops to generate the binary files it is the 'text' variable that is ultimately important.
I am not sure if it is of any use but shows that the bash shell can cope with binary...
Code:
#!/bin/bash --posix
# Creating a binary variable from a binary file...
> /tmp/SomeBinaryFile.dat
> /tmp/BinData.dat
# This loop is to give a usable 512 byte binary file only from 0x00 to 0xFF continuous repeated twice...
clear
echo "Generate a 512 byte binary file..."
echo ""
for character in $( seq 0 1 255 )
do
# Note:- The backticks and the four escape characters ARE required...
char=`printf '\\\\x'"%02x" $character`
printf "$char" >> /tmp/SomeBinaryfile.dat
done
for character in $( seq 0 1 255 )
do
# Do a repeat of the last loop, copy-n-paste is SOOO easy... ;o)
char=`printf '\\\\x'"%02x" $character`
printf "$char" >> /tmp/SomeBinaryfile.dat
done
# Now display the file information...
ls -l /tmp/SomeBinaryFile.dat
# Now do a HEX dump as proof...
echo ""
hexdump -C /tmp/SomeBinaryFile.dat
echo ""
# We are now going to create a variable with pseudo-zeros inside it. All other 8 bit values will eventually be real.
character=""
for subscript in $( seq 0 1 255 )
do
hexdata=`hexdump -n1 -s$subscript -v -e '1/1 "%02x"' /tmp/SomeBinaryFile.dat`
char=`printf '\\\\x'"$hexdata"`
if [ "$hexdata" == "00" ]
then
character=$character'\\0'
fi
character="$character$char"
done
# Repeat the above, copy-n-paste again... ;o)
for subscript in $( seq 256 1 511 )
do
hexdata=`hexdump -n1 -s$subscript -v -e '1/1 "%02x"' /tmp/SomeBinaryFile.dat`
char=`printf '\\\\x'"$hexdata"`
if [ "$hexdata" == "00" ]
then
# Note:- Two backslashes required here to generate the \0 reqired for the variable.
character=$character'\\0'
fi
character=$character$char
done
# Now generate the variable 'text' filled with binary except 0, this is changed to \0 inside the variable.
text=`echo -e -n "$character"`
echo -e -n "$text" > /tmp/BinData.dat
hexdump -C /tmp/BinData.dat
# Proof run.
echo -e "$text"
echo ""
echo "Length of string variable is ${#text} characters, NOT 512 characters..."
echo ""
echo "NOTE:- Zero, (00), is missing and replaced by real text '\0', as a"
echo "pseudo-zero. All other byte values exist..."
echo ""
Here is the display on a Macbook Pro 13" OSX 10.7.5 using the default Terminal.
Code:
Last login: Tue Aug 13 20:30:47 on ttys000
AMIGA:barrywalker~> ./bin_variable.sh
Generate a 512 byte binary file...
-rw-r--r-- 1 barrywalker wheel 512 13 Aug 21:19 /tmp/SomeBinaryFile.dat
00000000 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
00000010 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f |................|
00000020 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f | !"#$%&'()*+,-./|
00000030 30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f |0123456789:;<=>?|
00000040 40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f |@ABCDEFGHIJKLMNO|
00000050 50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f |PQRSTUVWXYZ[\]^_|
00000060 60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f |`abcdefghijklmno|
00000070 70 71 72 73 74 75 76 77 78 79 7a 7b 7c 7d 7e 7f |pqrstuvwxyz{|}~.|
00000080 80 81 82 83 84 85 86 87 88 89 8a 8b 8c 8d 8e 8f |................|
00000090 90 91 92 93 94 95 96 97 98 99 9a 9b 9c 9d 9e 9f |................|
000000a0 a0 a1 a2 a3 a4 a5 a6 a7 a8 a9 aa ab ac ad ae af |................|
000000b0 b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 ba bb bc bd be bf |................|
000000c0 c0 c1 c2 c3 c4 c5 c6 c7 c8 c9 ca cb cc cd ce cf |................|
000000d0 d0 d1 d2 d3 d4 d5 d6 d7 d8 d9 da db dc dd de df |................|
000000e0 e0 e1 e2 e3 e4 e5 e6 e7 e8 e9 ea eb ec ed ee ef |................|
000000f0 f0 f1 f2 f3 f4 f5 f6 f7 f8 f9 fa fb fc fd fe ff |................|
00000100 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
00000110 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f |................|
00000120 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f | !"#$%&'()*+,-./|
00000130 30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f |0123456789:;<=>?|
00000140 40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f |@ABCDEFGHIJKLMNO|
00000150 50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f |PQRSTUVWXYZ[\]^_|
00000160 60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f |`abcdefghijklmno|
00000170 70 71 72 73 74 75 76 77 78 79 7a 7b 7c 7d 7e 7f |pqrstuvwxyz{|}~.|
00000180 80 81 82 83 84 85 86 87 88 89 8a 8b 8c 8d 8e 8f |................|
00000190 90 91 92 93 94 95 96 97 98 99 9a 9b 9c 9d 9e 9f |................|
000001a0 a0 a1 a2 a3 a4 a5 a6 a7 a8 a9 aa ab ac ad ae af |................|
000001b0 b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 ba bb bc bd be bf |................|
000001c0 c0 c1 c2 c3 c4 c5 c6 c7 c8 c9 ca cb cc cd ce cf |................|
000001d0 d0 d1 d2 d3 d4 d5 d6 d7 d8 d9 da db dc dd de df |................|
000001e0 e0 e1 e2 e3 e4 e5 e6 e7 e8 e9 ea eb ec ed ee ef |................|
000001f0 f0 f1 f2 f3 f4 f5 f6 f7 f8 f9 fa fb fc fd fe ff |................|
00000200
00000000 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
00000010 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f |................|
00000020 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f | !"#$%&'()*+,-./|
00000030 30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f |0123456789:;<=>?|
00000040 40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f |@ABCDEFGHIJKLMNO|
00000050 50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f |PQRSTUVWXYZ[\]^_|
00000060 60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f |`abcdefghijklmno|
00000070 70 71 72 73 74 75 76 77 78 79 7a 7b 7c 7d 7e 7f |pqrstuvwxyz{|}~.|
00000080 80 81 82 83 84 85 86 87 88 89 8a 8b 8c 8d 8e 8f |................|
00000090 90 91 92 93 94 95 96 97 98 99 9a 9b 9c 9d 9e 9f |................|
000000a0 a0 a1 a2 a3 a4 a5 a6 a7 a8 a9 aa ab ac ad ae af |................|
000000b0 b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 ba bb bc bd be bf |................|
000000c0 c0 c1 c2 c3 c4 c5 c6 c7 c8 c9 ca cb cc cd ce cf |................|
000000d0 d0 d1 d2 d3 d4 d5 d6 d7 d8 d9 da db dc dd de df |................|
000000e0 e0 e1 e2 e3 e4 e5 e6 e7 e8 e9 ea eb ec ed ee ef |................|
000000f0 f0 f1 f2 f3 f4 f5 f6 f7 f8 f9 fa fb fc fd fe ff |................|
00000100 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
00000110 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f |................|
00000120 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f | !"#$%&'()*+,-./|
00000130 30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f |0123456789:;<=>?|
00000140 40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f |@ABCDEFGHIJKLMNO|
00000150 50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f |PQRSTUVWXYZ[\]^_|
00000160 60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f |`abcdefghijklmno|
00000170 70 71 72 73 74 75 76 77 78 79 7a 7b 7c 7d 7e 7f |pqrstuvwxyz{|}~.|
00000180 80 81 82 83 84 85 86 87 88 89 8a 8b 8c 8d 8e 8f |................|
00000190 90 91 92 93 94 95 96 97 98 99 9a 9b 9c 9d 9e 9f |................|
000001a0 a0 a1 a2 a3 a4 a5 a6 a7 a8 a9 aa ab ac ad ae af |................|
000001b0 b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 ba bb bc bd be bf |................|
000001c0 c0 c1 c2 c3 c4 c5 c6 c7 c8 c9 ca cb cc cd ce cf |................|
000001d0 d0 d1 d2 d3 d4 d5 d6 d7 d8 d9 da db dc dd de df |................|
000001e0 e0 e1 e2 e3 e4 e5 e6 e7 e8 e9 ea eb ec ed ee ef |................|
000001f0 f0 f1 f2 f3 f4 f5 f6 f7 f8 f9 fa fb fc fd fe ff |................|
00000200
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
Length of string variable is 514 characters, NOT 512 characters...
NOTE:- Zero, (00), is missing and replaced by real text '\0', as a
pseudo-zero. All other byte values exist...
AMIGA:barrywalker~> _
I appreciate that the _string_ is not an actual character zero, but the original code replaces character zero with two characters - "\0".
I am on holiday/vacation ATM so gimme a bit of time to INPUT to a variable with the two pseudo-zero characters for an actual character zero and 0xFF as a single byte, a total of three characters...
If I get stuck I will certainly admit it... ;o)
---------- Post updated 21-08-13 at 09:52 AM ---------- Previous update was 20-08-13 at 10:29 PM ----------
Hi DGPickett...
Slightly bigger than 3 bytes... ;o)
This generates a variable "text" 10 bytes long containing three "\0" pseudo-zeros and other non-ascii characters. The binary file generated is either 7 or 10 bytes in size......
Reading the bash man page, 'read -n 1' looks like a nice start. I am not sure what happens when you read a line feed or white space, so I guess I have to try it. I wrote all256 to put out bytes 0x00 through 0xff.
Dear Moderator
I am not able to post any new thread or post reply to mine old thread.
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Jaydeep (1 Reply)
Apologies for any typos, and IF this has been done before...
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