Kaylan,
There are two contexts for the export keyword here. Make supports an export
keyword, and the shell also support an export keyword. These two contexts are
separate and not related to each other in any way. When a *command* uses
export, its context is only within the shell assigned to run that command.
This is why you need to ensure that both the export command, and the following
command that uses the exported shell variable are both executed by the same
shell. Since each command is executed by a separate shell, you need to use a
semicolon and an optional backslash. If you don’t want to use a backslash, you
can simply append the two lines into one like this:
test:
export QA_STEP=start; touch ${QA_STEP}
Outside of *commands*, the word export is used to communicate that a *make*
variable should be exported to child processes of the current make process—so
that make variable will be available to child make processes – like this:
export QA_STEP_MAKE_VAR=start
test:
touch $(QA_STEP_MAKE_VAR)
Also note the difference in dereference syntax. Make variables are dereferenced
by make before the command is passed to the shell by using $() syntax, whereas
shell variables are dereferenced by the shell after it receives the command, by
using the ${} syntax.
John
From: kalyan [mailto:[email protected]]
Sent: Thursday, February 26, 2009 8:39 PM
To: John Calcote
Cc: albob; [email protected]
Subject: Re: Using environmnet variables in make
i guess backslash wouldnt work because export is not recognized as a shell
command in make..
Also, make manual hints that export can be used to communicate variables to
sub-make, so i am not sure if exporting a variable and using it in the same
makefile would work..
kalyan
On Fri, Feb 27, 2009 at 4:38 AM, John Calcote <[email protected]> wrote:
Alan,
Try adding a backslash after the export QA... statement like this:
test:
export QA_STEP=start; \
touch ${QA_STEP};
make executes each line in a separate shell, so QA_STEP will not be set in
the shell that executes the touch statement unless you execute both commands
in the same statement.
John
-----Original Message-----
From: [email protected]
[mailto:help-make-bounces+john.calcote
<mailto:help-make-bounces%2Bjohn.calcote> [email protected]] On Behalf Of albob
Sent: Thursday, February 26, 2009 10:28 AM
To: [email protected]
Subject: Using environmnet variables in make
Hi,
I have the following Makefile
.EXPORT_ALL_VARIABLES:
.SUFFIXES:
test:
export QA_STEP=start ;
touch ${QA_STEP};
Which I run using "gmake". This gives me:
slappy628: gmake test
export QA_STEP=qa_rtl ;
touch ;
touch: file arguments missing
Try `touch --help' for more information.
gmake: *** [test] Error 1
Can anyone tell me what I am doing wrong? No matter what I try I can not get
it to pick up on the environment variable set. Help would be much
appreciated.
Thanks
Alan
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