use batch file to insert string "NULL" ..

[adeline]

Basically i need to fill in some string on column that is NULL.. just insert NULL(string)

here is the scenario

input.txt

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field1      field2           field3
AAAA        BBBB             CCCC
DDDD                                  
EEEE        FFFF                  
GGGG                         HHHH     

Those empty one shall put a NULL inside
something like this,,

output.txt

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field1      field2           field3
AAAA        BBBB             CCCC
DDDD        NULL             NULL                           
EEEE        FFFF             NULL     
GGGG        NULL             HHHH     

## take note the field2 and field 3 space is different.. field 1 is almost with content hence the script just has to tackle field 2,3
My approach is to count the character until field 2 (12character from left) then check if is empty insert NULL. Then continue for field 3 (29 character from left) check if is empty insert null

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@echo off
set line =
for /F in(input.txt) do 
if "!line :~ 12" eq " " do 
write null     (i not sure whether is correct)
if "!line:~ 29 " eq " " do
write null   
echo  > output.txt 

Would appreciate if anyone can guide me on this..
thanks

[foxidrive]

This assumes the strings are fixed lengths with every line padded with spaces.

Edited:

Code: Select all

@echo off
setlocal enabledelayedexpansion
for /F "delims=" %%a in (input.txt) do (
set "line=%%a"
if "!line:~0,1!"==" " set "line=NULL!Line:~4!"
if "!line:~13,1!"==" " set "line=!line:~0,12!NULL!Line:~16!"
if "!line:~30,1!"==" " set "line=!line:~0,29!NULL"
echo >>"output.txt" !line!
)