Displaying variables batch file

Active Oldest Votes. You see the value being assigned to the variable, but then you can not access this value When a block of code code enclosed in parenthesis is parsed, all variable reads are replaced with the value in the variable before starting to execute the code, so, while executing, as there are no reads to the variable, if the value in the variable is changed inside the block the changed value can not be accessed.

Improve this answer. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Stack Gives Back Safety in numbers: crowdsourcing data on nefarious IP addresses. Featured on Meta. Batch language considers spaces to be acceptable parts of variable names. In order to prevent spaces, use quotation marks around the entire assignment; the variable name and value.

In batch files, variables can be used in any context, including as parts of commands or parts of other variables. You may not call a variable prior to defining it.

Unlike other programming languages, in a batch file a variable is substituted by its actual value before the batch script is run.

In other words, the substitution is made when the script is read into memory by the command processor, not when the script is later run. This enables the use of variables as commands within the script, and as part of other variable names in the script, etc.

The "script" in this context being a line - or block - of code, surrounded by round brackets:. In the above example, the ECHO command is evaluated as Hello when the script is read into memory, so the script will echo Hello forever, however many passes are made through the script. The way to achieve the more "traditional" variable behaviour of the variable being expanded whilst the script is running is to enable "delayed expansion".

This involves adding that command into the script prior to the loop instruction usually a FOR loop, in a batch script , and using an exclamation mark! Now, an advanced technique. Marketing preferences may be changed at any time. If a user's personally identifiable information changes such as your postal address or email address , we provide a way to correct or update that user's personal data provided to us.

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Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions. Brian Knittel discusses commands that are particularly effective in batch files and provides some examples of three categories of especially useful batch files. This chapter is from the book. Like scripts, batch files can serve as documentation of critical business procedures. Overview Pearson Education, Inc.

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