How Can I Replace Any Line by Its Line Number? - windows

Question

EDIT: After great help from #aschipfl, the code is %110 as functional as I wanted it to be! I did some extra research and made it easy to use with prompts for that extra %10 :P
#echo off
setlocal EnableExtensions DisableDelayedExpansion
rem // Create a prompt to set the variables
set /p _FILETYPE="What file type: "
set /p _LINENUM="Which line: "
set /p _NEWLINE="Make line say: "
rem // Start the loop, and set the files
for %%f in (*%_FILETYPE%) do (
set "_FILE=%%f"
echo "_FILE=%%f"
rem // To execute seperate code before the end of the loop, starting at ":subroutine".
call :subroutine "%%f"
)
:subroutine
rem // Write to a temporary file:
> "%_FILE%.new" (
rem /* Loop through each line of the original file,
rem preceded by the line number and a colon `:`:*/
for /F "delims=" %%A in ('findstr /N "^" "%_FILE%"') do (
rem // Store the current line with prefix to a variable:
set "LN=%%A"
rem /* Store the line number into another variable;
rem everything up to the first non-numeric char. is regarded,
rem which is the aforementioned colon `:` in this situation: */
set /A "NUM=LN"
rem // Toggle delayed expansion to avoid trouble with `!`:
setlocal EnableDelayedExpansion
rem /* Compare current line number with predefined one and replace text
rem in case of equality, or return original text otherwise: */
if !NUM! equ %_LINENUM% (
echo(!_NEWLINE!
) else (
rem // Remove line number prefix:
echo(!LN:*:=!
)
endlocal
)
)
rem // Move the edited file onto the original one:
move /Y "%_FILE%.new" "%_FILE%"
endlocal
exit /B
ORIGINAL QUESTION:
Doesn't matter whats in any of the lines already. I just want to be able to pick any line from a .txt and replace it with whatever I choose.
So for example: Maybe I have a bunch of .txt's, and I want to replace line 5 in all of them with "vanilla". And later choose to replace line 10 of all .txt's with "Green". And so on...
I've seen lots of people asking the same main question. But I keep finding situational answers.
"How do I replace specific lines?" "you search for whats already in the line, and replace it with your new text" -I cant have that. I need it to be dynamic, because whats in each "line 5" is different, or there's lots of other lines with the same text.
I had tried the only one answer I could find, but all it ended up doing is replace literally all lines with "!ln:*:=!", instead of echoing.
#echo off
setlocal disableDelayedExpansion
set "file=yourFile.txt"
set "newLine5=NewLine5Here"
>"%file%.new" (
for /f "delims=" %%A in ('findstr /n "^" "%file%"') do for /f "delims=:" %%N in ("%%A") do (
set "ln=%%A"
setlocal enabableDelayedExpansion
if "!ln:~0,6!" equ "5:FMOD" (echo(!newLine5!) else echo(!ln:*:=!
endlocal
)
)
move /y "%file%.new" "%file%" >nul

Answer 1

The following (commented) code should work for you:
#echo off
setlocal EnableExtensions DisableDelayedExpansion
rem // Define constants here:
set "_FILE=yourFile.txt"
set "_NEWLINE=NewLine5Here"
set /A "_LINENUM=5" & rem // (target line number)
rem // Write to a temporary file:
> "%_FILE%.new" (
rem /* Loop through each line of the original file,
rem preceded by the line number and a colon `:`:*/
for /F "delims=" %%A in ('findstr /N "^" "%_FILE%"') do (
rem // Store the current line with prefix to a variable:
set "LN=%%A"
rem /* Store the line number into another variable;
rem everything up to the first non-numeric char. is regarded,
rem which is the aforementioned colon `:` in this situation: */
set /A "NUM=LN"
rem // Toggle delayed expansion to avoid trouble with `!`:
setlocal EnableDelayedExpansion
rem /* Compare current line number with predefined one and replace text
rem in case of equality, or return original text otherwise: */
if !NUM! equ %_LINENUM% (
echo(!_NEWLINE!
) else (
rem // Remove line number prefix:
echo(!LN:*:=!
)
endlocal
)
)
rem // Move the edited file onto the original one:
move /Y "%_FILE%.new" "%_FILE%"
endlocal
exit /B
Besides the typo in EnableDelayedExpansion in your code, you do not even need a second for /F loop to get the line number, and you do not need to extract a certain number of characters from the prefixed line text.
Note that this approach fails for line numbers higher than 231 - 1 = 2 147 483 647.

Answer 2

...is replace literally all lines with "!ln:*:=!", instead of echoing.
But that's correct, because the FINDSTR /N prefixes each line with a line number before.
The !ln:*:=! only removes the line number again.
And the findstr trick is used to avoid skipping of empty lines or lines beginning with ; (the EOL character).
The !line:*:=! replaces everthing up to the first double colon (and incuding it) with nothing.
This is better than using FOR "delims=:" because delims=: would also strip double colons at the front of a line.
The toggling of delayed expansion is necessary to avoid accidential stripping of ! and ^ in the line set "ln=%%A"
To fix your code:
setlocal DisableDelayedExpansion
for /f "delims=" %%A in ('findstr /n "^" "%file%"') do (
set "ln=%%A"
setlocal EnableDelayedExpansion
if "!ln:~0,6!" equ "5:FMOD" (
set "out=!newLine5!"
) else (
set "out=!ln:*:=!"
)
echo(!out!
endlocal
)