call variable from Makefile

[rajkumarmadhani]

Hi,

I declared variable in Makefile
like
BUILD_DATE = $(shell date +'%Y%m%d')

i want to use this variable in c.

example :test.c

main()
{
printf("date:%s\n",BUILD_DATE);

}
how to do this ...

[TSangeetha]

Hey,
You can do an export for the variable which u have defined in the Makefile using the below command,
"export BUILD_DATE"
Now the variable defined in the makefile will become an environment variable and it will be available for access by the other programs.
In the c program you can use the API getenv(BUILD_DATE) to get the value of the variable BUILD_DATE.

FYI, I have not checked it.

Hi,

I declared variable in Makefile
like
BUILD_DATE = $(shell date +'%Y%m%d')

i want to use this variable in c.

example :test.c

main()
{
printf("date:%s\n",BUILD_DATE);

}
how to do this ...

[rajkumarmadhani]

Compilation is in one machine ....
Actual execution in other machine is it works?

[alf55]

Hi,

I declared variable in Makefile
like like to know

BUILD_DATE = $(shell date +'%Y%m%d')

i want to use this variable in c.

example :test.c

main()
{
printf("date:%s\n",BUILD_DATE);

}

how to do this ...

BUILD_DATE = $(shell date +'%Y%m%d')

.o:.c
     gcc -c -DBUILD_DATE=$(BUILD_DATE)

main()
{
printf("date:%s\n",BUILD_DATE);

}

[voidpointer69]

There is also the "-D" flag available...

[rajkumarmadhani]

BUILD_DATE = $(shell date +'%Y%m%d')
BUILD_NUM = $(shell cat $(PROG_BUILD_NUM))
CFLAGS = -DBUILD_DATE=$(BUILD_DATE) -DBUILD_NUM=$(BUILD_NUM)

app:$(OBJS)
$(CC) $(CFLAGS) -o app $(OBJS)


still iam getting error like below.

test.c:35: error: 'BUILD_DATE' undeclared (first use in this function)
test.c:35: error: (Each undeclared identifier is reported only once
test.c:35: error: for each function it appears in.)
test:36: error: 'BUILD_NUM' undeclared (first use in this function)

[alf55]

The problem is that the "BUILD_DATE" passed in is not a string and it needs to be converted into a string to be printed.

Sample file "code.c"

#include <stdlib.h>
#include <stdio.h>
#include <stdlib.h>

#define Str(arg) #arg

#define StrValue(arg) Str(arg)

#define STR_BUILD_DATE StrValue(BUILD_DATE)

char build_date[] = STR_BUILD_DATE;

int main() {
    fprintf(stdout,"%s\n", build_date);
    return 0;
}

gcc -o code -DBUILD_DATE=20110811   code.c
./code

gcc -o code -DBUILD_DATE=20101102  code.c
./code