int main()
{
int card_val = assign_val();
return 0;
}
int main()
{
int t=100;
int *p;
int *q=&t;
p=&t;
//*p say as goto address stored in p
//*p is the value stored at the memory address stored in the block p
//t |10| at address 12345
//p |12345| at address 12353
//*p dereferences the address stored at p and fetches the value at that address.
//that is why while running this code, only difference in o/p is values of &p &q are different.
// because they are different pointer vars at different memory locations
printf("&t = %u\t, *p = %d\t, &p = %u\t, p = %u\t\n",&t, *p, &p, p);
printf("&t = %u\t, *q = %d\t, &q = %u\t, q = %u\t\n",&t, *q, &q, q);
//////////////////arithmatic////////////////////////////
int n[3] = {12,22,43};
int *int_p = n; // for array , u can use name of array as reference to the start of the block of memory, where, array resides
printf("++*int_p=%u\n", ++*int_p);//prints 13, * has preced over +, so forst derefer value at int_p, ie 12, the ++12 = 13
printf("*++int_p=%u\n", *++int_p);//prints 22, *(++int_p) = *(&(n+1)) = 22, now int_p points to int_p+1, ie 4 bytes agter int_p,
//now, int_p = &n[1]
printf("*(int_p+1)=%u\n", *(int_p+1));//prints 43,
printf("*(int_p+1)=%u\n", *(int_p+2));//prints garbage, since out of array print.
//////////////////////pass by reference////////////////////////////
int a=1, b=10;
printer(&a, &b);
printf("a=%d,b=%d\n",a,b);
/////////////////return struct//////////////////////////////////
//check out the struct and the function assign_val() at the top.
//
COORD *point; // declares a pointer of type COORD
point = assign_val(); // assign_val returns a 'pointer' to COORD XXX not a COORD object, so assigned to a pointer
printf("x=%f,y=%f,z=%f\n", (point)->x, point->y, point->z); // xyz are accessed in this fashion
///////////////////////////////////////////////////////alternate techniue
COORD pnt;
pnt = *assign_val();
printf("x=%f,y=%f,z=%f\n", pnt.x, pnt.y, pnt.z);
// so use '->' for accesing struct vars with a object pointer,
// so use '.' for accesing struct vars with a normal object,
///////////////////array and pointers////////////////////////////
char achr[] = {'R', 'o', 'n', '\0'};
char *c_p;
c_p= achr; // points to the first elem of char array
printf ("name = %c\n", *c_p);
printf("Elems: ");
for (int i=0;i<strlen(achr);i++)
{
printf("%c", *c_p);
c_p++;
}
printf("\n");
/*
pointers and arrays are different:
A pointer is a variable. We can do
pa = a and pa++.
An Array is not a variable. a = pa and a++ ARE ILLEGAL.
*/
////////////////////////////////////////////////Array of Pointers///////////////////////////////////////
//declare array with text seperated by \n
char s_b[] = {"pallavi\n"};
char s_c[] = {"priyal\n"};
char s_a[] = {"nilesh\n"};
char *s_d = {"ronak\n"};//this is a legal operation
printf("String %d =%s\n",1,s_d);//Thats how u print a string using pointers
char *ptr_arr[] = {s_a, s_b, s_c, s_d};
for (int x = 0; x< 4; x++){
printf("String %d =%s\n",x+1,ptr_arr[x]);
}
printf("\n comp val:%d",strcmp(s_b,s_c));
printf("\n");
//////////////////////////////////////////////////END/////////////////////////////////////////////////
return 0;
}
/*
* Failover the gtm ------------------------------------------------------
*/
int
failover_gtm(void)
{
char date[MAXTOKEN+1];
char *stdIn;
int rc;
FILE *f;
elog(INFO, "Failover gtm\n");
if (!isVarYes(VAR_gtmSlave) || (sval(VAR_gtmSlaveServer) == NULL) || is_none(sval(VAR_gtmSlaveServer)))
{
elog(ERROR, "ERROR: GTM slave is not configured. Cannot failover.\n");
return(1);
}
if (do_gtm_ping(sval(VAR_gtmSlaveServer), atoi(sval(VAR_gtmSlavePort))) != 0)
{
elog(ERROR, "ERROR: GTM slave is not running\n");
return(1);
}
/* Promote the slave */
elog(NOTICE, "Running \"gtm_ctl promote -Z gtm -D %s\"\n", sval(VAR_gtmSlaveDir));
rc = doImmediate(sval(VAR_gtmSlaveServer), NULL,
"gtm_ctl promote -Z gtm -D %s", sval(VAR_gtmSlaveDir));
if (WEXITSTATUS(rc) != 0)
{
elog(ERROR, "ERROR: could not promote gtm (host:%s, dir:%s)\n", sval(VAR_gtmSlaveServer), sval(VAR_gtmSlaveDir));
return 1;
}
/* Configure promoted gtm */
if ((f = prepareLocalStdin(newFilename(stdIn), MAXPATH, NULL)) == NULL)
return(1);
fprintf(f,
"#===================================================\n"
"# Updated due to GTM failover\n"
"# %s\n"
"startup = ACT\n"
"#----End of reconfiguration -------------------------\n",
timeStampString(date, MAXTOKEN+1));
fclose(f);
elog(NOTICE, "Updating gtm.conf at %s:%s\n", sval(VAR_gtmSlaveServer), sval(VAR_gtmSlaveDir));
rc = doImmediate(sval(VAR_gtmSlaveServer), stdIn, "cat >> %s/gtm.conf", sval(VAR_gtmSlaveDir));
if (WEXITSTATUS(rc) != 0)
{
elog(ERROR, "ERROR: could not update gtm.conf (host: %s, dir:%s)\n", sval(VAR_gtmSlaveServer), sval(VAR_gtmSlaveDir));
return 1;
}
/* Update and backup configuration file */
if ((f = prepareLocalStdin(stdIn, MAXPATH, NULL)) == NULL)
return(1);
fprintf(f,
"#===================================================\n"
"# pgxc configuration file updated due to GTM failover\n"
"# %s\n"
"gtmMasterServer=%s\n"
"gtmMasterPort=%s\n"
"gtmMasterDir=%s\n"
"gtmSlave=n\n"
"gtmSlaveServer=none\n"
"gtmSlavePort=0\n"
"gtmSlaveDir=none\n"
"#----End of reconfiguration -------------------------\n",
timeStampString(date, MAXTOKEN+1),
sval(VAR_gtmSlaveServer),
sval(VAR_gtmSlavePort),
sval(VAR_gtmSlaveDir));
fclose(f);
rc = doImmediate(NULL, stdIn, "cat >> %s", pgxc_ctl_config_path);
if (WEXITSTATUS(rc) != 0)
{
elog(ERROR, "ERROR: could not update gtm.conf (host: %s, dir:%s)\n", sval(VAR_gtmSlaveServer), sval(VAR_gtmSlaveDir));
return 1;
}
freeAndReset(stdIn);
backup_configuration();
/* Reconfigure myself */
assign_val(VAR_gtmMasterServer, VAR_gtmSlaveServer); reset_var(VAR_gtmSlaveServer);
assign_val(VAR_gtmMasterPort, VAR_gtmSlavePort); reset_var(VAR_gtmSlavePort);
assign_val(VAR_gtmMasterDir, VAR_gtmSlaveDir); reset_var(VAR_gtmSlaveDir);
assign_sval(VAR_gtmSlaveServer, "none");
assign_sval(VAR_gtmSlavePort, "0");
assign_sval(VAR_gtmSlaveDir, "none");
assign_sval(VAR_gtmSlave, "n");
return 0;
}