CODEWITHSUNDEEP
batch-fileif-statement
Raider00321
Raider00321

Reputation: 57

Batch File conditional statement not working correctly

So i am attempting to make a simple script to check if an application is running using a external text file (using 1 and 0 for if running or is not). However i cannot seem to get the statement working correctly..

setlocal enabledelayedexpansion

set /p Running=<IsRunning.txt
IF %Running% EQU 0(GOTO ProgramNotRunning)
IF %Running% EQU 1(GOTO ProgramRunning)


:ProgramNotRunning
echo program starting
echo 0 >IsRunning.txt
echo 1 >IsRunning.txt
GOTO:EOF

:ProgramRunning
echo program already running
GOTO:EOF

The issue is no matter what value it is, it always only ever runs the ProgramNotRunning code block and not the other.

Prior to using EQU, i was simply using == to check for equivilance.

Much thanks for any assistance given!

Upvotes: 1

Views: 420

Answers (1)

MC ND
MC ND

Reputation: 70961

1 - Missing spaces

If %Running% EQU 0 (...
                  ^ This space is needed

2 - In batch files lines of code are executed one after the other unless one command changes this behaviour. You can iterate with for, jump with goto, call subroutines with call, leave the batch, the subroutine or the console with exit, ... but a label will not break the execution. After your if %Running% EQU 1 ... there isn't anything that prevent execution to continue into the code following code it none of the if tests find a coincidence. So, if the set /p does not retrieve 0 or 1 the code after :ProgramNotRunning will be always executed.

3 - Missing/empty file. If IsRunning.txt can not be found or it is empty (or at least the first line is empty) or if it does contain an unexpected value, the if lines will fail. The code executed is

file missing    :   if   EQU 0 (
line/file empty :   if   EQU 0 (
bad data        :   if this is a test EQU 0 (

All this cases will cause the line to be considered an error and the execution will be canceled. 

@echo off
    setlocal enableextensions disabledelayedexpansion

    rem Retrieve running state
    set "Running="
    if exist "IsRunning.txt" ( 
        set /p "Running=" < "IsRunning.txt" 
    )

    IF "%Running%" EQU "0" goto ProgramNotRunning 
    IF "%Running%" EQU "1" goto ProgramRunning 

    rem As there is no valid data, assume the program is not running

:ProgramNotRunning
    echo program starting
    >"IsRunning.txt" (echo 1)
    goto :eof

:ProgramRunning
    echo program already running
    goto :eof

Why >"IsRunning.txt" (echo 1)? Just to be sure there are no aditional spaces after the 1 that will be included in the output (as happens with your code), retrieved when the line is readed from the file and causing the if to fail

if "1 " EQU "1" ( ...    This will be evaluated to false

And this still leaves cases where the data retrieved can make the code fail. For a 0/1 test, it is easier to not read the file, just test for presence of the file. If the file exist, the program is running, else it is not running.

Upvotes: 2

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