Set errorlevel in Windows batch file

Question

I am writing a batch script that will loop through each line of a text file, (each line containing a filename) check if the file exists and then runs the file and moves it.

Answer 1

@ECHO OFF
SETLOCAL
DEL output.txt 2>nul
REM Loop through each line of input.txt
FOR /F "tokens=1-3 delims=, " %%i IN (.\ready\input.txt) DO (
  ECHO.
  ECHO.
  ECHO.
  ECHO Check %%i exists, set error flag if it doesnt
  if exist .\ready\%%i (set "errorflag=") ELSE (set errorflag=2)
CALL echo return code is %%errorflag%%

  ECHO Run %%i if it exists
  if NOT DEFINED errorflag (
   call .\ready\%%i
   ECHO Move %%i to archive if no error occured
   if errorlevel 1 (SET errorflag=3) ELSE (ECHO copy .\ready\%%i .\archive\%mydate%_%mytime%_%%j_%%k_%%i)
  )
  ECHO Copy line of text to the new output.txt file if an error occured
  if DEFINED errorflag >>output.txt ECHO %%i, %%j, %%k
)
GOTO :EOF

Here's a rewritten procedure.

Note: output.txt is deleted at the start, else the >> would append to any existing file. 2>nul suppresses error messages if the delete fails (eg. file not exist)

Within a block statement (a parenthesised series of statements), the ENTIRE block is parsed and THEN executed. Any %var% within the block will be replaced by that variable's value AT THE TIME THE BLOCK IS PARSED - before the block is executed.

Hence, IF (something) else (somethingelse) will be executed using the values of %variables% at the time the IF is encountered.

Two common ways to overcome this are 1) to use setlocal enabledelayedexpansion and use !var! in place of %var% to access the chnaged value of var or 2) to call a subroutine to perform further processing using the changed values.

Note therefore the use of CALL ECHO %%var%% which displays the changed value of var. CALL ECHO %%errorlevel%% displays, but sadly then RESETS errorlevel.

IF DEFINED var is true if var is CURRENTLY defined.

ERRORLEVEL is a special varable name. It is set by the system, but if set by the user, the user-assigned value overrides the system value.

IF ERRORLEVEL n is TRUE if errorlevel is n OR GREATER THAN n. IF ERRORLEVEL 0 is therefore always true.

The syntax SET "var=value" (where value may be empty) is used to ensure that any stray spaces at the end of a line are NOT included in the value assigned.

The required commands are merely ECHOed for testing purposes. After you've verified that the commands are correct, change ECHO COPY to COPY to actually copy the files.

I used the following input.txt:

seterr1.bat, J1, K1
seterr5.bat,J2,K2
seterr0.bat,J3 K3
seterr5.bat, J4, K4
notexist.bat, J5, K5

With existing files seterr*.bat which contain

@ECHO OFF
EXIT /b 1

(where the 1 in the last line determines the errorlevel returned)

and received the resultant output:

Check seterr1.bat exists, set error flag if it doesnt
return code is 
Run seterr1.bat if it exists
Move seterr1.bat to archive if no error occured
Copy line of text to the new output.txt file if an error occured

Check seterr5.bat exists, set error flag if it doesnt
return code is 
Run seterr5.bat if it exists
Move seterr5.bat to archive if no error occured
Copy line of text to the new output.txt file if an error occured

Check seterr0.bat exists, set error flag if it doesnt
return code is 
Run seterr0.bat if it exists
Move seterr0.bat to archive if no error occured
copy .\ready\seterr0.bat .\archive\__J3_K3_seterr0.bat
Copy line of text to the new output.txt file if an error occured

Check seterr5.bat exists, set error flag if it doesnt
return code is 
Run seterr5.bat if it exists
Move seterr5.bat to archive if no error occured
Copy line of text to the new output.txt file if an error occured

Check notexist.bat exists, set error flag if it doesnt
return code is 2
Run notexist.bat if it exists
Copy line of text to the new output.txt file if an error occured

Note that the COPY is merely ECHOed as I mentioned earlier.

and output.txt

seterr1.bat, J1, K1
seterr5.bat, J2, K2
seterr5.bat, J4, K4
notexist.bat, J5, K5