Originally posted by yishanju at 2009-2-5 06:14 PM:
if /? 就有啊
Sir, I'm still not very familiar with using if together with it.
I did read the help, but I'm not very clear on what ERRORLEVEL values REG returns!! ^^
Performs conditional processing in batch programs.
IF ERRORLEVEL number command
IF string1==string2 command
IF EXIST filename command
NOT Specifies that Windows should carry out the command only if
the condition is false.
ERRORLEVEL number Specifies a true condition if the last program run returned
an exit code equal to or greater than the number specified.
string1==string2 Specifies a true condition if the specified text strings
match.
EXIST filename Specifies a true condition if the specified filename
exists.
command Specifies the command to carry out if the condition is
met. Command can be followed by ELSE command which
will execute the command after the ELSE keyword when
the specified condition is false.
The ELSE clause must occur on the same line as the command after the IF. For
example:
IF EXIST filename. (
del filename.
) ELSE (
echo filename. missing.
)
The following would NOT work because the del command needs to be terminated by
a newline:
IF EXIST filename. del filename. ELSE echo filename. missing
Nor would the following work, since the ELSE command must be on the same line
as the end of the IF command:
IF EXIST filename. del filename.
ELSE echo filename. missing
The following would work if you want it all on one line:
IF EXIST filename. (del filename.) ELSE echo filename. missing
If Command Extensions are enabled IF changes as follows:
IF string1 compare-op string2 command
IF CMDEXTVERSION number command
IF DEFINED variable command
where compare-op may be one of:
EQU - equal
NEQ - not equal
LSS - less than
LEQ - less than or equal
GTR - greater than
GEQ - greater than or equal
and the /I switch, if specified, says to do case-insensitive string compares.
The /I switch can also be used on the string1==string2 form of IF. These
comparisons are generic, in that if both string1 and string2 are comprised of
numeric digits only, the strings are converted to numbers and a numeric
comparison is performed.
The CMDEXTVERSION conditional works just like ERRORLEVEL, except it is
comparing against an internal version number associated with the Command
Extensions. The first version is 1. It will be incremented by one when
significant enhancements are added to the Command Extensions. The
CMDEXTVERSION conditional is never true when Command Extensions are disabled.
The DEFINED conditional works just like EXISTS except it takes an environment
variable name and returns true if the environment variable is defined.
%ERRORLEVEL% will expand into a string representation of the current
value of ERRORLEVEL, provided that there is not already an environment
variable with the name ERRORLEVEL, in which case you'll get its value.
After running a program, the following illustrates ERRORLEVEL use:
goto answer %ERRORLEVEL%
:answer0
echo Program had return code 0
:answer1
echo Program had return code 1
You can also use the numerical comparisons above:
IF %ERRORLEVEL% LEQ 1 goto okay
%CMDCMDLINE% will expand into the original command line passed to CMD.EXE
prior to any processing by CMD.EXE, provided that there is not already
an environment variable with the name CMDCMDLINE, in which case you'll
get its value.
%CMDEXTVERSION% will expand into a string representation of the
current value of CMDEXTVERSION, provided that there is not already
an environment variable with the name CMDEXTVERSION, in which case you'll
get its value.
