Sooner or later every batch files creator faces the
problem of checking the result of one command execution before executing the
other one. For that we have built-in variable “errorlevel” that changes its
value after each command execution. Its value can vary for different commands
used in batch files. Usually successful execution of the command is displayed
as zero value of variable, but not always other value implies any errors. So if
you create batch file, you should
remember about this meaning of errorlevel.
This variable is used as follows:
if errorlevel 0 echo Errorlevel
is 0 or greater
Instead of “echo
Errorlevel is 0 or greater” you can put any necessary command. After “if” you
can add “not” (no quotation marks for this time again) – then the value becomes
diametrically opposed. It should be mentioned that “errorlevel N”-construction does not mean precise equality of
variable “errorlevel” to value N. It means that the command will be executed
only in case “errorlevel” value is or is greater than N. Thus it is more
convenient to check errors with the help of “if errorlevel” –construction than to execute the command
successfully. But if you write “if not
errorlevel 1”, that means in case “errorlevel” is nonnegative, we obtain
the result of “errorlevel” equal to zero. Unfortunately nonnegative values of
this variable are not guaranteed. For more details you can read about “if errorlevel” –construction in Windows
help manual.
