using a variable between 2 programs

[itzsug]

hi,

i have 2 C programs prog1.c and prog2.c. i have compiled them separately using gcc. i have the executables prog1 and prog2. i want to set a value for a variable in prog1.c and should be able to access the value of the same variable in prog2.c.

prog1 and prog2 would be continously running.

how can achieve this?

thanks

from
jagadish

[cddvd]

well, i gues you have to store your variable/value some where between your two programs so that you can access from both the programs, why don dont you try storing your variable value in a file separately and you can open this file in any program you want and access the value

[itzsug]

Hi cddvd,

thanks a lot for the information. The thing the value of the variable is changed many times. So do u think using a file would be feasible? can u suggest any other possibility?

thanks

-Jagadish

Hello Jagadish!

I think it is quite obvious that a \"buffer\" should be used to stored the value of the variable whose value changes frequently. This \"buffer\", or a temporary memory location, can be
1. A file
2. Database
3. Memory Location
4. Attribute Indicators/Flags

Since you are coding in C, the language allows better control over memory allocations and usage unlike Java! The technique I am proposing, is only theoretical. I haven\'t implemented it. It is your responsibility to try!

Assign Memory Location for variable DATA (using malloc() or some other library function). Assign Memory Location for variable FLAG.

Assuming there are two programs in the memory, PROG1 and PROG2, and if DATA changes in PROG1, then point PROG2 variables to the same memory location as DATA and FLAG. A flag can be just a boolean! If DATA from PROG1 changes, then set the FLAG to true and update DATA. From PROG2, run a thread every 20 seconds or whatever time period you want, to keep checking the FLAG. If the FLAG state changes, then retrieve the data from DATA variable.

I hope you understand what I am trying to say! This is just pseudo-code.

Good luck.

[bnaveens]

you may also try creating a shared memory area and putting that variable in there.

[deepakmenon181]

if ur using linux for running ur program then use Named pipe or fifo.
there is a system call to create a Named pipe(fifo).
so ur prog1 should create the fifo and write the value to it.
then the prog2 can read the value from fifo.
there are other techniques --queue,shared memory,rpc etc .
but using a fifo is more simpler.

[kishleo]

yeah you can use memory locations but i dont advice you to use the memory location coz you have the chance of loosing data once if something goes wrong with the system. if you use the database or files you can have your value there all the time.

[vijaykumarreddy]

u can use extern keyword to store the value which u want to use in more than one program try for help on extern by typing extern in the c editor and pressing ctrl+F1

i dont know the exact process
but i am sure it will work
try it
all the best
use the variable with preceding extern keyword in the declaration part
if it works plz post me
thank u

[priyaraji]

Hi,
Since the value of the variable in prog1.c is going to be always edited what you could do is make the value of the variable in prog1.c to be written into a file and make prog2.c to read the value of the variable from this file.You can use this using file handling functions in C

Sripriya

[rahul246]

hi kishleo,
can you give me your contact no.. there is something i need to talk about the post in the ustechsolutions forum. I need to remove my email ID from this post, can you help me in that ?
You are the moderator of that group, so this can be done only by you..
anurag