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Top Forums Shell Programming and Scripting Optimised way for search & replace a value on one line in a very huge file (File Size is 24 GB). Post 302552410 by binlib on Friday 2nd of September 2011 10:59:56 PM
Old 09-02-2011
As yazu has pointed out, if you are replacing the same number of bytes (or you can pad), you can use lower level programing, or do it with dd:
Code:
echo NEW |dd of=your-file bs=1 seek=offset-of-OLD count=3 conv=notrunc

You may need to adjust your options to dd if you are not using GNU dd. Be careful with this command, the original file is changed directly.
 

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DD(1)							      General Commands Manual							     DD(1)

NAME
dd - disk dumper SYNOPSIS
dd [option = value] ... EXAMPLES
dd if=/dev/fd0 of=/dev/fd1 # Copy disk 0 to disk 1 dd if=x of=y bs=1w skip=4 # Copy x to y, skipping 4 words dd if=x of=y count=3 # Copy three 512-byte blocks DESCRIPTION
This command is intended for copying partial files. The block size, skip count, and number of blocks to copy can be specified. The options are: if = file - Input file (default is stdin) of = file - Output file (default is standard output) ibs = n - Input block size (default 512 bytes) obs = n - Output block size (default is 512 bytes) bs = n - Block size; sets ibs and obs (default is 512 bytes) skip = n - Skip n input blocks before reading seek = n - Skip n output blocks before writing count = n - Copy only n input blocks conv = lcase - Convert upper case letters to lower case conv = ucase - Convert lower case letters to upper case conv = swab - Swap every pair of bytes conv = noerror- Ignore errors and just keep going conv = silent- Suppress statistics (Minix specific flag) Where sizes are expected, they are in bytes. However, the letters w, b, or k may be appended to the number to indicate words (2 bytes), blocks (512 bytes), or K (1024 bytes), respectively. When dd is finished, it reports the number of full and partial blocks read and writ- ten. SEE ALSO
vol(1). DD(1)
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