loop through file saving to variable - windows

Question

I now have the following bat file working (which allows one to add text to the end of each line of a file) -- please see also:
bat file: Use of if, for and a variable all together
#echo off
setLocal EnableDelayedExpansion
IF EXIST "%FileToModify1%" (
for /f "tokens=* delims= " %%a in (%FileToModify1%) do (
echo %%a Note: certain conditions apply >> "%SaveFile1%"
)
)
However, I would like to save each line to a variable (including the new line symbol(s)) and then echo the variable to a file at the end. Since there are several lines in the file it is really inefficient to save to a file with each line.
I tried googling this, but the answers do not fit my situation...
essentially I need the syntax for concatenating and saving to a variable (cumulatively like "+=" in C#), and also using the new lines...

Answer 1

Actually you do not need to put everything into a variable, you just need to place the redirection at another position.
Try this:
#echo off
setlocal EnableDelayedExpansion
if exist "%FileToModify1%" (
for /F "usebackq delims=" %%a in ("%FileToModify1%") do (
echo %%a Note: certain conditions apply
)
) > "%SaveFile1%"
endlocal
Note that empty lines in the original file are ignored by for /F, so they are not transferred to the new file. Also lines starting with ; are ignored by for /F (unless you change the eol option -- see for /?).
I modified the for /F options:
no delims are allowed, so the each line is output as is (with "tokens=* delims= ", leading spaces are removed from each line if present);
usebackq allows to surround the file specification in "" which is helpful if it contains spaces;
Appendix A
If you still want to store the file content into a variable, you can do this:
#echo off
setlocal EnableDelayedExpansion
rem the two empty lines after the following command are mandatory:
set LF=^
if exist "%FileToModify1%" (
set "FileContent="
for /F "usebackq delims=" %%a in ("%FileToModify1%") do (
set "FileContent=!FileContent!%%a Note: certain conditions apply!LF!"
)
(echo !FileContent!) > "%SaveFile1%"
)
endlocal
The file content is stored in variable FileContent, including the appendix Note: certain conditions apply. LF holds the new-line symbol.
Note:
The length of a variable is very limited (as far as I know, 8191 bytes since Windows XP and 2047 bytes earlier)!
[References:
Store file output into variable (last code fragment);
Explain how dos-batch newline variable hack works]
Appendix B
Alternatively, you could store the file content in a array, like this:
#echo off
setlocal EnableDelayedExpansion
if exist "%FileToModify1%" (
set /A cnt=0
for /F "usebackq delims=" %%a in ("%FileToModify1%") do (
set /A cnt+=1
set "Line[!cnt!]=%%a Note: certain conditions apply"
)
(for /L %%i in (1,1,!cnt!) do (
echo !Line[%%i]!
)) > "%SaveFile1%"
)
endlocal
Each line of the file is stored in an array Line[1], Line[2], Line[3], etc., including the appendix Note: certain conditions apply. cnt contains the total number of lines, which is the array size.
Note:
Actually this is not a true array data type as such does not exist in batch, it is a collection of scalar variables with an array-style naming (Line[1], Line[2],...); therefore one might call it pseudo-array.
[References:
Store file output into variable (first code fragment);
How to create an array from txt file within a batch file?]

Answer 2

you can write the output file in one shot:
(
for /l %%i in (0,1,10) do (
echo line %%i
)
)>outfile.txt
(much quicker than appending each line separately)