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POProblems reading simple numeric values from files in Windows batch files
 

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  1. POProblems reading simple numeric values from files in Windows batch files
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    <p>My colleague and I have been pulling our hair out all day over this.</p> <p>We have a simple Windows batch file. We want it to read from a text file whose file path we are generating programmatically, take the single numeric value in this file, and compare it to a local variable. But we're getting completely inexplicable behavior.</p> <p>The file contains a single scalar number, such as the number 2. Here's the code:</p> <pre><code>ThisAppFlagFileName=foo.txt if not exist "%HOMEPATH%\ourcompanyname\%ThisAppFlagFileName%" ( ECHO do something here ) else ( SET /P InstalledVersion=&lt;"%HOMEPATH%\ourcompanyname\%ThisAppFlagFileName%" ECHO We think the file contains: %InstalledVersion% IF %InstalledVersion% GEQ %ThisVersionInstallDataNum% ( ECHO Version %ThisVersion% of the %ThisAppVisibleName% has already been installed for this user; exiting. GOTO TheEnd ) ) :TheEnd Echo END </code></pre> <p>We keep getting an error reading <code>2 was unexpected at this time.</code> So we inserted some trace message and, just in case the <code>else</code> was problematic, stuck to two different <code>if</code> statements:</p> <pre><code>ThisAppFlagFileName=foo.txt if not exist "%HOMEPATH%\ourcompanyname\%ThisAppFlagFileName%" ( ECHO do something here ) ECHO Trace Message 1 before IF if exist "%HOMEPATH%\ourcompanyname\%ThisAppFlagFileName%" ( ECHO Trace Message 2 after IF before CD SET /P InstalledVersion=&lt;%HOMEPATH%\ourcompanyname\%ThisAppFlagFileName%" ECHO We think the file contains: %InstalledVersion% IF %InstalledVersion2% GEQ %ThisVersionInstallDataNum% ( ECHO Version %ThisVersion% of the %ThisAppVisibleName% has already been installed for this user; exiting. GOTO TheEnd ) ) :TheEnd Echo END </code></pre> <p>And we see <em>only</em> the first trace message (before the <code>if</code> statement), and <em>not</em> the second trace message. So our conclusion is that somehow the <em>content</em> of the file is being interpolated into the line <code>if exist "%HOMEPATH%\ourcompanyname\%ThisAppFlagFileName%"</code>, but of course we don't understand why the first <code>if not exist</code> works but the second doesn't.</p> <p>Can anyone spot the mistake, please? Environment is Windows 7 <code>cmd.exe</code> window, but we are hoping to deploy to both Windows 7 and Windows XP.</p>
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    1. COYou're not reading the content of the file at all. You're setting `InstalledVersion` to `<` plus the filename (`<%ThisAppFlagFileName%`). `<` does not redirect in a `SET` assignment. You need to use a `for /f` loop to actually read the content of the file. (You can confirm this from a command prompt - type `set something=<foo.txt` from a prompt in the folder where `foo.txt` is located, and then type `set something`.)
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      1. POProblems reading simple numeric values from files in Windows batch files
      1. USKen White
    2. COApologies. I forgot the /p switch. I have edited the code. Online references had indicated SET /p does accept <. Will look up and try your approach.
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      1. USjbeldock
    3. CO`SET /P something=<foo.txt` (with an existing file, of course) results in "The system cannot find the file specified" (DOS error 2). I can't find any reference that says that `SET /P` accepts redirection, either.
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      1. USKen White
 

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