Shared memory C questions(size,structures
So im new to C and I've got some questions about shared memory.
Im using different .c to use the shm.
This is the program where i create the memory
int id = shmget( 1234, CONSTANT*sizeof(structure),IPC_CREAT | 0666 );
exit_on_error (id, "Error");
SO my question is how in another program can I acess this memory and know that "CONSTANT"
I have something like this
int id = shmget(1234, 0,0);
exit_on_error (id, "Error");
*/structure pointer*/ sp = (structure*) shmat(id,0,0);
exit_on_null (structure pointer,"Error");
But now I need that constant in order to iterate on the number of "objects" of the structure and edit the objects
c shared-memory shared
asked Nov 23 '18 at 18:42
VenturaVentura
236
add a comment |
So im new to C and I've got some questions about shared memory.
Im using different .c to use the shm.
This is the program where i create the memory
int id = shmget( 1234, CONSTANT*sizeof(structure),IPC_CREAT | 0666 );
exit_on_error (id, "Error");
SO my question is how in another program can I acess this memory and know that "CONSTANT"
I have something like this
int id = shmget(1234, 0,0);
exit_on_error (id, "Error");
*/structure pointer*/ sp = (structure*) shmat(id,0,0);
exit_on_null (structure pointer,"Error");
But now I need that constant in order to iterate on the number of "objects" of the structure and edit the objects
c shared-memory shared
asked Nov 23 '18 at 18:42
VenturaVentura
236
Maybe you could add sizeof(size_t) to your allocation size. Use these extra-bytes and place the value of CONSTANT at the beginning of the shared memory buffer, then you can read it on the other process and proceed with your iteration.
– BlueStrat
Nov 23 '18 at 18:55
add a comment |
So im new to C and I've got some questions about shared memory.
Im using different .c to use the shm.
This is the program where i create the memory
int id = shmget( 1234, CONSTANT*sizeof(structure),IPC_CREAT | 0666 );
exit_on_error (id, "Error");
SO my question is how in another program can I acess this memory and know that "CONSTANT"
I have something like this
int id = shmget(1234, 0,0);
exit_on_error (id, "Error");
*/structure pointer*/ sp = (structure*) shmat(id,0,0);
exit_on_null (structure pointer,"Error");
But now I need that constant in order to iterate on the number of "objects" of the structure and edit the objects
c shared-memory shared
asked Nov 23 '18 at 18:42
VenturaVentura
236
So im new to C and I've got some questions about shared memory.
Im using different .c to use the shm.
This is the program where i create the memory
int id = shmget( 1234, CONSTANT*sizeof(structure),IPC_CREAT | 0666 );
exit_on_error (id, "Error");
SO my question is how in another program can I acess this memory and know that "CONSTANT"
I have something like this
int id = shmget(1234, 0,0);
exit_on_error (id, "Error");
*/structure pointer*/ sp = (structure*) shmat(id,0,0);
exit_on_null (structure pointer,"Error");
But now I need that constant in order to iterate on the number of "objects" of the structure and edit the objects
c shared-memory shared
c shared-memory shared
asked Nov 23 '18 at 18:42
VenturaVentura
236
asked Nov 23 '18 at 18:42
VenturaVentura
236
asked Nov 23 '18 at 18:42
VenturaVentura
236
asked Nov 23 '18 at 18:42
VenturaVentura
236
asked Nov 23 '18 at 18:42
VenturaVentura
236
236
Maybe you could add sizeof(size_t) to your allocation size. Use these extra-bytes and place the value of CONSTANT at the beginning of the shared memory buffer, then you can read it on the other process and proceed with your iteration.
– BlueStrat
Nov 23 '18 at 18:55
add a comment |
Maybe you could add sizeof(size_t) to your allocation size. Use these extra-bytes and place the value of CONSTANT at the beginning of the shared memory buffer, then you can read it on the other process and proceed with your iteration.
– BlueStrat
Nov 23 '18 at 18:55
Maybe you could add sizeof(size_t) to your allocation size. Use these extra-bytes and place the value of CONSTANT at the beginning of the shared memory buffer, then you can read it on the other process and proceed with your iteration.
– BlueStrat
Nov 23 '18 at 18:55
Maybe you could add sizeof(size_t) to your allocation size. Use these extra-bytes and place the value of CONSTANT at the beginning of the shared memory buffer, then you can read it on the other process and proceed with your iteration.
– BlueStrat
Nov 23 '18 at 18:55
add a comment |
1 Answer
1
active
oldest
votes
There is a function, shmctl() which takes a command, IPC_STAT, and fills in a structure shmid_ds which describes the object.
answered Nov 23 '18 at 18:50
mevetsmevets
2,215718
add a comment |
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There is a function, shmctl() which takes a command, IPC_STAT, and fills in a structure shmid_ds which describes the object.
answered Nov 23 '18 at 18:50
mevetsmevets
2,215718
add a comment |
There is a function, shmctl() which takes a command, IPC_STAT, and fills in a structure shmid_ds which describes the object.
answered Nov 23 '18 at 18:50
mevetsmevets
2,215718
add a comment |
There is a function, shmctl() which takes a command, IPC_STAT, and fills in a structure shmid_ds which describes the object.
answered Nov 23 '18 at 18:50
mevetsmevets
2,215718
There is a function, shmctl() which takes a command, IPC_STAT, and fills in a structure shmid_ds which describes the object.
answered Nov 23 '18 at 18:50
mevetsmevets
2,215718
answered Nov 23 '18 at 18:50
mevetsmevets
2,215718
answered Nov 23 '18 at 18:50
mevetsmevets
2,215718
answered Nov 23 '18 at 18:50
mevetsmevets
2,215718
2,215718
add a comment |
add a comment |
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Maybe you could add sizeof(size_t) to your allocation size. Use these extra-bytes and place the value of CONSTANT at the beginning of the shared memory buffer, then you can read it on the other process and proceed with your iteration.
– BlueStrat
Nov 23 '18 at 18:55