Insert bytes into file using shell

Question

I would like to use a linux shell (bash, zsh, etc.) to insert a set of known bytes into a file at a certain position. Similar questions have been asked, but they modify in-place the bytes of a file. These questions don't address inserting new bytes at particular positions.

For example, if my file has a sequence of bytes like \x32\x33\x35 I might want to insert \x34 at position 2 so that this byte sequence in the file becomes \x32\x33\x34\x35.

oguz ismail · Accepted Answer · 2019-04-24 02:44:30Z

3

You can achieve this using head, tail and printf together. For example; to insert \x34 at position 2 in file:

{ head -c 2 file; printf '\x34'; tail -c +3 file; } > new_file

_{For POSIX-compliance, \064 (octal representation of \x34) can be used.}

To make this change in-place, just move new_file to file.

No matter which tool(s) you use, this operation will cost lots of CPU time for huge files.

edited Apr 24, 2019 at 2:44

answered Apr 24, 2019 at 1:58

oguz ismail

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