Batch not-equal (inequality) operator
Batch FileOperatorsBatch File Problem Overview
According to this, !==! is the not-equal string operator.
Trying it, I get:
C:\> if "asdf" !==! "fdas" echo asdf
!==! was unexpected at this time.
What am I doing wrong?
Batch File Solutions
Solution 1 - Batch File
Try
if NOT "asdf" == "fdas" echo asdf
Solution 2 - Batch File
Use NEQ instead.
if "asdf" NEQ "fdas" echo asdf
Solution 3 - Batch File
I know this is quite out of date, but this might still be useful for those coming late to the party. (EDIT: updated since this still gets traffic and @Goozak has pointed out in the comments that my original analysis of the sample was incorrect as well.)
I pulled this from the example code in your link:
IF !%1==! GOTO VIEWDATA
REM IF NO COMMAND-LINE ARG...
FIND "%1" C:\BOZO\BOOKLIST.TXT
GOTO EXIT0
REM PRINT LINE WITH STRING MATCH, THEN EXIT.
:VIEWDATA
TYPE C:\BOZO\BOOKLIST.TXT | MORE
REM SHOW ENTIRE FILE, 1 PAGE AT A TIME.
:EXIT0
!%1==! is simply an idiomatic use of == intended to verify that the thing on the left, that contains your variable, is different from the thing on the right, that does not. The ! in this case is just a character placeholder. It could be anything. If %1 has content, then the equality will be false, if it does not you'll just be comparing ! to ! and it will be true.
!==! is not an operator, so writing "asdf" !==! "fdas" is pretty nonsensical.
The suggestion to use if not "asdf" == "fdas" is definitely the way to go.
Solution 4 - Batch File
Try:
if not "asdf" == "fdas" echo asdf
That works for me on Windows XP (I get the same error as you for the code you posted).
Solution 5 - Batch File
NEQ is usually used for numbers and == is typically used for string comparison.
I cannot find any documentation that mentions a specific and equivalent inequality operand for string comparison (in place of NEQ). The solution using IF NOT == seems the most sound approach. I can't immediately think of a circumstance in which the evaluation of operations in a batch file would cause an issue or unexpected behavior when applying the IF NOT == comparison method to strings.
I wish I could offer insight into how the two functions behave differently on a lower level - would disassembling separate batch files (that use NEQ and IF NOT ==) offer any clues in terms of which (unofficially documented) native API calls conhost.exe is utilizing?
Solution 6 - Batch File
The easiest way I found is to:
IF %ERRORLEVEL% NEQ 0 Echo An error was found
or
IF %ERRORLEVEL% GRT 0 goto error1
The operator !==! has not right value, which means that's used only to know whether a variable was set or not.
IF !%1==! GOTO main