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Changing a special line and Byte in a random file

 
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# 1  
Old 06-17-2014
Changing a special line and Byte in a random file
Hello
I created 3 files by:
dd if=/dev/urandom bs=1024 count=1000000 of=./testfile1
dd if=/dev/urandom bs=1024 count=5000000 of=./testfile2
dd if=/dev/urandom bs=1024 count=10000000 of=./testfile3

Now I want to know how to make a change in a specific byte and/or line of theses files?

# 2  
Old 06-17-2014
The concept of "line" in a file made of random garbage data has no meaning.

One way to change byte 13 of testfile1 to "A":

Code:
echo "A" | dd bs=1 conv=notrunc seek=13 count=1 of=testfile1

This User Gave Thanks to Corona688 For This Post:
frhling
# 3  
Old 06-17-2014
Expanding on garbage data - /dev/urandom writes random bytes 0-255. ASCII 10 is a newline, ASCII12 is a pagefeed, there are others. When you write these kinds of characters any old place you get lines, pagefeeds, backspaces, and other stuff any old place.

Lines have no meaning in this context. These are not carriage-control text files they are binary.
 
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