checking hte existence of an environment variable

[Kok Yong Lee]

Hi there,

Would like to know what is the best way to determine whether an environment
variable has been set in a batch file. I dont care about its value just
wanted to know whetehr user has previously set it.

thanks in advanced

 

[Mark V]

Hi there,

Would like to know what is the best way to determine whether an
environment variable has been set in a batch file. I dont care
about its value just wanted to know whetehr user has previously
set it.

thanks in advanced

IF /?

"The DEFINED conditional works just like EXISTS except it takes an
environment variable name and returns true if the environment
variable is defined." (W2K)

 

[Kok Yong Lee]

Thanks Mark

However, with the new IF DEFINED loop, I find it the batch script behave
differently. For example, in the code snippet below, if I detected env
variable asm_main_location is set, I will call another batch file to set
some env varible then use the env varible to create a folder.

With the IF DEFINED loop, for some reason the %ASMFULL% env variable dont
get recognise and hence no folder is created, but at the end of the batch
script I can clear see that %ASMFULL% is set via SET ASMFULL.

And if I comment out the IF DEFINED loop, then the batch script will go
ahead and create a new folder based on the ASMFULL value.

any ideas what may have been wrong with my script?

set asm_main_location=blah
echo [Setting 3rd Party Environment]
if DEFINED asm_main_location (
call R:\build\versions.bat /o
if not exist %_INV_3RD_PARTY_LOCALDIR%\ASM\%ASMFULL% (
mkdir %_INV_3RD_PARTY_LOCALDIR%\ASM\%ASMFULL%
) else (
echo Folder %_INV_3RD_PARTY_LOCALDIR%\ASM\%ASMFULL% existed already
)
)
echo [Finish Setting Environment]

 

[kk]

if "%asm_main_location%"=="" (
REM environment variable does not exist
..
) else (
REM environment variable exists
..
)

Thanks Mark

However, with the new IF DEFINED loop, I find it the batch script behave
differently. For example, in the code snippet below, if I detected env
variable asm_main_location is set, I will call another batch file to set
some env varible then use the env varible to create a folder.

With the IF DEFINED loop, for some reason the %ASMFULL% env variable dont
get recognise and hence no folder is created, but at the end of the batch
script I can clear see that %ASMFULL% is set via SET ASMFULL.

And if I comment out the IF DEFINED loop, then the batch script will go
ahead and create a new folder based on the ASMFULL value.

any ideas what may have been wrong with my script?

set asm_main_location=blah
echo [Setting 3rd Party Environment]
if DEFINED asm_main_location (
call R:\build\versions.bat /o
if not exist %_INV_3RD_PARTY_LOCALDIR%\ASM\%ASMFULL% (
mkdir %_INV_3RD_PARTY_LOCALDIR%\ASM\%ASMFULL%
) else (
echo Folder %_INV_3RD_PARTY_LOCALDIR%\ASM\%ASMFULL% existed already
)
)
echo [Finish Setting Environment]

IF /?

"The DEFINED conditional works just like EXISTS except it takes an
environment variable name and returns true if the environment
variable is defined." (W2K)

 

[Al Dunbar [MS-MVP]]

Thanks Mark

However, with the new IF DEFINED loop, I find it the batch script behave
differently. For example, in the code snippet below, if I detected env
variable asm_main_location is set, I will call another batch file to set
some env varible then use the env varible to create a folder.

With the IF DEFINED loop, for some reason the %ASMFULL% env variable dont
get recognise and hence no folder is created, but at the end of the batch
script I can clear see that %ASMFULL% is set via SET ASMFULL.

And if I comment out the IF DEFINED loop, then the batch script will go
ahead and create a new folder based on the ASMFULL value.

any ideas what may have been wrong with my script?

just before the call r:\build\version.bat /o command is executed, ALL of the
variables up to the matching ")" are expanded. You may change their values,
either directly or indirectly via a call to another batch. What you need to
do is replace those "%" signs with "!", and add the following command at the
top of the batch file:

setlocal enabledelayedexpansion

/Al

set asm_main_location=blah
echo [Setting 3rd Party Environment]
if DEFINED asm_main_location (
call R:\build\versions.bat /o
if not exist %_INV_3RD_PARTY_LOCALDIR%\ASM\%ASMFULL% (
mkdir %_INV_3RD_PARTY_LOCALDIR%\ASM\%ASMFULL%
) else (
echo Folder %_INV_3RD_PARTY_LOCALDIR%\ASM\%ASMFULL% existed already
)
)
echo [Finish Setting Environment]

IF /?

"The DEFINED conditional works just like EXISTS except it takes an
environment variable name and returns true if the environment
variable is defined." (W2K)

 

[Al Dunbar [MS-MVP]]

just before the call r:\build\version.bat /o command is executed, ALL of the
variables up to the matching ")" are expanded. You may change their values,
either directly or indirectly via a call to another batch. What you need to
do is replace those "%" signs with "!", and add the following command at the
top of the batch file:

Oooops, typo alert. I meant to say above "... via a call to another batch,
but you will not be able to display those new values from within the "( )"
block.

/Al

setlocal enabledelayedexpansion

/Al

set asm_main_location=blah
echo [Setting 3rd Party Environment]
if DEFINED asm_main_location (
call R:\build\versions.bat /o
if not exist %_INV_3RD_PARTY_LOCALDIR%\ASM\%ASMFULL% (
mkdir %_INV_3RD_PARTY_LOCALDIR%\ASM\%ASMFULL%
) else (
echo Folder %_INV_3RD_PARTY_LOCALDIR%\ASM\%ASMFULL% existed already
)
)
echo [Finish Setting Environment]

In microsoft.public.win2000.cmdprompt.admin Kok Yong Lee wrote:

Hi there,

Would like to know what is the best way to determine whether an
environment variable has been set in a batch file. I dont care
about its value just wanted to know whetehr user has previously
set it.

thanks in advanced

IF /?

"The DEFINED conditional works just like EXISTS except it takes an
environment variable name and returns true if the environment
variable is defined." (W2K)