I have the following two structs where "child struct" has a "rusage struct" as an element.
Then I create two structs of type "child" let's call them childA and childB
How do I copy just the rusage struct from childA to childB?
typedef struct{
int numb;
char *name;
pid_t pid;
long userT;
long systemT;
struct rusage usage;
}child;
typedef struct{
struct timeval ru_utime; /* user time used */
struct timeval ru_stime; /* system time used */
long ru_maxrss; /* maximum resident set size */
long ru_ixrss; /* integral shared memory size */
long ru_idrss; /* integral unshared data size */
long ru_isrss; /* integral unshared stack size */
long ru_minflt; /* page reclaims */
long ru_majflt; /* page faults */
long ru_nswap; /* swaps */
long ru_inblock; /* block input operations */
long ru_oublock; /* block output operations */
long ru_msgsnd; /* messages sent */
long ru_msgrcv; /* messages received */
long ru_nsignals; /* signals received */
long ru_nvcsw; /* voluntary context switches */
long ru_nivcsw; /* involuntary context switches */
}rusage;
I did the following, but I guess it copies the memory location, because if I changed the value of usage in childA, it also changes in childB.
memcpy(&childA,&childB, sizeof(rusage));
I know that gives childB all the values from childA. I have already taken care of the others fields in childB, I just need to be able to copy the rusage struct called usage that resides in the "child" struct.
To perform a deep copy you must first free any memory that was being pointed to by the destination structure. Then allocate enough memory to hold the strings pointed to by the source structure. Now, strncpy the strings over.
If the structures are of compatible types, yes, you can, with something like: memcpy (dest_struct, source_struct, sizeof (*dest_struct)); The only thing you need to be aware of is that this is a shallow copy.
A deep copy, in contrast, means that you copy an entire object (struct). If it has members that can be copied shallow or deep, you also make a deep copy of them.
1) Add a declaration structure * pStructure; to your code. 2) Add pStructure = (structure *) array; ` right after array's declaration. 3) Then, at the line where the memcpy is, set a breakpoint.
Simply:
childB.usage = childA.usage;
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