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Editing big file in UNIX

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# 1  
Old 08-12-2014
Display Editing big file in UNIX
Hi Guys,
I have a hugefile. I have requirement to change Indicator from "T" to "P" or from "P" to "T" which comes in header itself. I could not open either in any of editors or in UNIX command line using vi as file size > 3GB

Please suggest a solution as how to achieve it through script or any single line commands.

Note: This indicator comes in ISA 15 segment.

Example:

Code:
ISA*00* *00* *08*92 *08*123*030627*1304*U*00*00*0*P*>~


I have change it to

Code:
ISA*00* *00* *08*92 *08*123*030627*1304*U*00*00*0*T*>~

Last edited by Corona688; 08-12-2014 at 03:01 PM..
# 2  
Old 08-12-2014
Please use code tags for code, [code]stuff[/code]. Or select the text you wish to wrap and hit the Image button.

Do I understand you to mean that you wish to change exactly one character in the very first line of this file?

Editing the original file is fraught with danger. One mistake and you've trashed 3GB of data. Do you have backups?
# 3  
Old 08-13-2014
Yes you understanding is correct. I just need to change one character in file which comes in ISA 15 segment. Segment delimter is "*".
I have back up of file so no worries
# 4  
Old 08-13-2014
Are the field sizes for the 1st 15 ISA segments all fixed-width (or more importantly, is the "P" you want to change always the 51st character on the line)?

What is the maximum length of the 1st line in this file (in bytes)?

Will you tell your script you want that segment to be "T" or "P"? Or, is your script supposed to find the character that is there and reverse it?
Last edited by Don Cragun; 08-13-2014 at 10:07 AM.. Reason: Add another question.
# 5  
Old 08-13-2014
The total length of first file is 106 bytes. This indicator comes in 103 position. The script can be interactive such as

Enter the folder:
Enter the file name:
Change from T to P: Y/N
Change from P to T: Y/N
# 6  
Old 08-13-2014
Quote:
Originally Posted by Abdulhameed M
The total length of first file is 106 bytes.
??? You told us they are 2 GIGAbytes, far too large to edit.

Quote:
This indicator comes in 103 position.
??? You show it in position 51!

I'm not going to make wild guesses about the true nature of your data. Edit this script as you see fit. It works for the line you posted.

Code:
# Read first line of file
IFS="" read -r LINE < hugefile

# Check the 51st character
case "${LINE:50:1}" in
P)
        Z="T";
        ;;
T)
        Z="P";
        ;;
*)
        echo "$LINE has nothing valid to change"
        exit 1
        ;;
esac

printf "Change ${LINE:50:1} to ${Z} [Y/N] "

# Try read -n 1 REPLY, if you don't want it to wait for ENTER key.
read REPLY

[ "$REPLY" = "Y" ] || exit


printf "%s" "${LINE:0:50}${Z}${LINE:51}" | dd of=hugefile conv=notrunc

Last edited by Corona688; 08-13-2014 at 11:11 AM..
# 7  
Old 08-13-2014
Thanks for your quick reply.. I will test and get back..
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