Batch - Combining Two Pieces of Text on One Line in a Loop - loops

Question

I'm trying to work up a batch file to combine two pieces of text on one line. The first is the filename; the second is the first line of text beginning with "To: ". I have been struggling for hours and this is as far as I've gotten:
#echo off
IF EXIST fullnames.txt DEL fullnames.txt
FOR /F %%g IN ('dir /b *.eml') DO (
SET filename=%~f1
SET toline=FINDSTR /B /C "To: "
ECHO %FILENAME%%TOLINE% >> fullnames.txt
)
and it doesn't work. I am getting errors or incorrect results almost regardless of what I put down for the filename line; haven't even begun to test the toline part. Any suggestions?

Answer 1

You already used FOR /F to capture the output of the DIR command. Capturing the output of FINDSTR is no different.
However, it is more efficient to use a simple FOR in place of the FOR /F with the DIR command.
You used %~f1 when I think you intended %%~fg.
You cannot expand a variable set within parentheses using %var%, you must use !var! delayed expansion instead. Type SET /? from the command line for more information - read the section starting with "Finally, support for delayed environment variable expansion has been
added..."
However, in your case, you can easily avoid using delayed expansion (not that it is a problem).
Instead of deleting any existing "fullnames.txt" and then appending output to it, it is more efficient to enclose the entire construct within parentheses and redirect all output to the file using the over-write mode.
#echo off
(
for %%F in (*.eml) do (
for "delims=" %%A in ('findstr /b /c:"To: " "%%F"') do echo %%F %%A
)
) >fullnames.txt
But the above solution, simple as it is, is much more complicated than it needs to be.
FINDSTR can process multiple files specified with wildcards, and it will prefix each matching line with the filename followed by a colon.
You can get your results simply from the command line without even using a batch file (or you could put this in a batch file):
findstr /b /c:"To: " *.eml >fullnames.txt
Edit
If you are concerned that a file might contain multiple lines starting with "To: ", and you only want to use the first line, then it is back to using a batch file:
#echo off
setlocal enableDelayedExpansion
set "prevFile="
(
for /f "tokens=1* delims=:" %%A in ('findstr /b /c:"To: " *.eml') do (
if "%%A" neq "!prevFile!" echo %%A: %%B
set "prevFile=%%A"
)
) >fullnames.txt
The above solution could fail if a filename contains !. Also, a path could be used with *.eml as long as the path does not contain a drive letter. Both the drive and ! issues can be resolved with additional modifications.

Answer 2

#echo off
setlocal EnableDelayedExpansion
if exist fullnames.txt del fullnames.txt
for %%f in (*.eml) do (
set toline=
for /F "delims=" %%l in ('findstr /B /C:"To: " "%%f"') do (
if not defined toline set "toline=%%l"
)
echo %%f!toline! >> fullnames.txt
)
EDIT: Simpler method added
The set toline= command delete 'toline' variable before each file is processed, so just the first "To: " matching line found is assigned to it and later shown using Delayed Expansion. However, this process may be achieved in a simpler way that doesn't require Delayed Expansion, as dbenham suggested:
#echo off
if exist fullnames.txt del fullnames.txt
for %%f in (*.eml) do (
set firstFind=
for /F "delims=" %%l in ('findstr /B /C:"To: " "%%f"') do (
if not defined firstFind set firstFind=now & echo %%f%%l >> fullnames.txt
)
)

Answer 3

You can't assign and use environment variables inside a for loop. Use delayed variable expansion or call a subroutine.
Delayed would look something like this
setlocal EnableDelayedExpansion
#echo off
IF EXIST fullnames.txt DEL fullnames.txt
FOR /F %%g IN ('dir /b *.eml') DO (
SET filename=%~f1
SET toline=FINDSTR /B /C "To: "
ECHO !FILENAME!!TOLINE! >> fullnames.txt
)
However, that doesn't look like it would work correctly anyway. I would do it like this
FOR /F %%g IN ('dir /b *.eml') DO call :process %%g
goto :eof
:process
SET filename=%~f1
SET toline=FINDSTR /B /C "To: "
ECHO %FILENAME%%TOLINE% >> fullnames.txt