delete bytes from file Post: 302071174

Sponsored Content

Top Forums Shell Programming and Scripting delete bytes from file Post 302071174 by Loriel on Thursday 13th of April 2006 03:35:07 AM

04-13-2006

Registered User

The actual code has 17 offsets to process, but for my test run, I just used two. Also, keep in mind it never made it through the first cycle. I know the cycle was working (the apptest2 file kept growing, kb-by-slow-kb), but it's just too slow considering the total app size is 11 MB.

Code:

offsets=(0x5766ee 0xb020ae)
length1=(8 8)
length2=(5 5)
replace=(HOCUS POKUS)

for ((i=0;$i<${#offsets[@]};i++)); do
# Enter in the correct value
    printf ${replace[$i]} | dd bs=1 count="${length2[$i]}" seek="${offsets[$i]}" conv=notrunc of=apptest
# Create the infile
    dd if=apptest bs=1 count="$((${offsets[$i]}+${length2[$i]}))" of=apptest2
# Splice infile into original
    dd bs=1 skip="$((${offsets[$i]}+${length1[$i]}))" seek="$((${offsets[$i]}+${length2[$i]}))" of=apptest2
# Replace original so we can cycle
    mv apptest2 apptest
done

I tried using the printf approach to appending the infile, but that changes the filetype of the end result, which ruins the application. I didn't know if I could use dd to append to the end, so I simply changed the order to enter the correct value first, then cut up the file. That part of the loop works in a fraction of a second. It's the infile (and I suspect the splicing, as well) that takes so long.

Loriel

View Public Profile for Loriel

Find all posts by Loriel

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

Take a file from the system and put on tape and reset the file to 0 bytes

:mad: I did this the other day but one of my support personnel removed my history so i could call it back up to remeber the exact command since i am air-headed at times. I am trying to take a 30 MEG file off the system and drop it to tape then i want to make the file go back to being 0 bytes so...

2. Programming

How to delete N bytes from the starting of the file from a C function???

Hi, I want to delete the initial few lines (or even bytes) from a file. I want to do this from a C function & this is in Linux platform. The truncate & ftruncate is allowing me to delete bytes from the end only. Any linux C function calls or ideas or any suggestions?? I'm in a dead...

3. Shell Programming and Scripting

How to delete initial N bytes from the starting of the file using sed?

I want to delete initial N bytes of a file using sed. How can I do that?

4. Shell Programming and Scripting

Remove first N bytes and last N bytes from a binary file on AIX.

Hi all, Does anybody know or guide me on how to remove the first N bytes and the last N bytes from a binary file? Is there any AWK or SED or any command that I can use to achieve this? Your help is greatly appreciated!! Best Regards, Naveen.

5. UNIX for Dummies Questions & Answers

Bytes of character in file

Hi, How do I check for the total bytes of character used by a file? Can I used a od command to check? Thanks.

6. Shell Programming and Scripting

Error PHP Fatal error: Allowed memory size of 67108864 bytes exhausted(tried to allocate 401 bytes)

While running script I am getting an error like Few lines in data are not being processed. After googling it I came to know that adding such line would give some memory to it ini_set("memory_limit","64M"); my input file size is 1 GB. Is that memory limit is based on RAM we have on...

7. Programming

Copying 1024 bytes data in 3-bytes chunk

Hi, If I want to copy a 1024 byte data stream in to the target location in 3-bytes chunk, I guess I can use the following script. dd bs=1024 count=3 if=/src of=/dest But, I would like to know, how to do it via a C program. I have tried this with memcpy(), that did not help.

8. UNIX for Dummies Questions & Answers

X bytes of 0, Y bytes of random data, Z bytes of 5, T bytes of 1. ??

Hello guys. I really hope someone will help me with this one.. So, I have to write this script who: - creates a file home/student/vmdisk of 10 mb - formats that file to ext3 - mounts that partition to /mnt/partition - creates a file /mnt/partition/data. In this file, there will...

9. Shell Programming and Scripting

Shell script - entered input(1-40 bytes) needs to be converted exactly 40 bytes

hello, suppose, entered input is of 1-40 bytes, i need it to be converted to 40 bytes exactly. example: if i have entered my name anywhere between 1-40 i want it to be stored with 40 bytes exactly. enter your name: donald duck (this is of 11 bytes) expected is as below - display 11...

10. Shell Programming and Scripting

Get file's first x bytes

is there a better way to do this: head -c 10000k /var/dump.log | head -c 6000k unfortunately, the "-c" option is not available on sun solaris. so i'm looking at "dd". but i dont know how to use it to achieve the same exact goal as the above head command. this needs to work on both solaris...

LEARN ABOUT DEBIAN

editdiff

REDIFF(1)							     Man pages								 REDIFF(1)

NAME

       rediff, editdiff - fix offsets and counts of a hand-edited diff

SYNOPSIS

       rediff ORIGINAL EDITED

       rediff EDITED

       rediff {[--help] | [--version]}

       editdiff FILE

       editdiff {[--help] | [--version]}

DESCRIPTION

       You can use rediff to correct a hand-edited unified diff. Take a copy of the diff you want to edit, and edit it without changing any
       offsets or counts (the lines that begin "@@"). Then run rediff, telling it the name of the original diff file and the name of the one you
       have edited, and it will output the edited diff file but with corrected offsets and counts.

       A small script, editdiff, is provided for editing a diff file in-place.

       The types of changes that are currently handled are:

       o   Modifying the text of any file content line (of course).

       o   Adding new line insertions or deletions.

       o   Adding, changing or removing context lines. Lines at the context horizon are dealt with by adjusting the offset and/or count.

       o   Adding a single hunk (@@-prefixed section).

       o   Removing multiple hunk (@@-prefixed sections).

       Alternatively, if only one argument is provided, it is taken to be the edited file and the counts and offsets are adjusted as appropriate.
       Some assumptions are made when used in this mode. See recountdiff(1) for more information.

OPTIONS

       --help
	   Display a short usage message.

       --version
	   Display the version number of rediff.

SEE ALSO

       interdiff(1), recountdiff(1)

AUTHOR

       Tim Waugh <twaugh@redhat.com>
	   Package maintainer

patchutils							    13 May 2002 							 REDIFF(1)