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?
This question is related to
batch-file
operators
Try
if NOT "asdf" == "fdas" echo asdf
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?
I know this is quite out of date, but this might still be useful for those coming late to the party.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.
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).
Use NEQ instead.
if "asdf" NEQ "fdas" echo asdf
Source: Stackoverflow.com