How do I create a file with a given structure?

Question

How do I create a file that has X bytes of 0, Y bytes of the number 7 (i.e. 0x07 in hex, 00000111 in binary), Z random bytes and T bytes of the number 25(0x19 in hex, 00011001 in binary). Finally, this file should be of size X+Y+Z+T bytes.

Answer 1

Install 'ghex' from the software center.

Go to a terminal and run touch hexfile.

Open ghex, then open the 'hexfile'.

Press insert, then type the bytes you want.

Save.

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You might be able to do save something like this in a file, change the varibles (as instructed), and make it executable (chmod +x filename), then run it ./filename.

#!/bin/bash
#(C) 2011 Erik B. Andersen This script is licensed under the latest non-draft
#version of the AGPL as published by the Free Software Foundation (currently 
#at http://www.gnu.org/licenses/) .
# Set the following four variables.
X=
Y=
Z=
T=
#######Don't need to change anything past here.
y=0
t=0
head -c $X /dev/zero >> structurefile
while [ $y -lt $Y ]; do echo -n -e "\x07"; y=$(($y+1)); done >> structurefile
head -c $Z /dev/urandom >> structurefile
while [ $t -lt $T ]; do echo -n -e "\x19"; t=$(($t+1)); done >> structurefile