IF
Performs conditional processing in batch programs.
IF [NOT] ERRORLEVEL number command
IF [NOT] string1==string2 command
IF [NOT] EXIST filename command
NOT Specifies that Windows XP 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 if 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 [/I] 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 both comprised of all numeric digits, then 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.
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
will get its value instead. 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 using 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 will get its value instead.
%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
will get its value instead.
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