How to interact with 2 databases in C using MySQL? -

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i working on project have count runners. @ point, have transfer data local database (mysqllocal) 1 of high school i'm working in (mysqllycee).

i think doing idea, reason have segfault when executing program.

#include <stdio.h> #include <stdlib.h> #include <sys/socket.h> #include <arpa/inet.h> #include <netdb.h> #include <netinet/in.h> #include <unistd.h> #include <string.h> #include <mysql.h>   int main(int argc, char *argv[]){     mysql mysqllocal;     mysql_res *result = null;     mysql_row row;     char requete[150];     int num_champs;     char noparticipant[5];     char kmparcourus[3];     mysql_init(&mysqllocal);     if(!mysql_real_connect(&mysqllocal,"127.0.0.1","root","debianccf","localccf",0,null,0))printf("error on first connect");      sprintf(requete,"select no_participant, kmparcourus participants no_course = %s",argv[5]);     if(!mysql_query(&mysqllocal,requete))printf("error on first query");     result = mysql_use_result(&mysqllocal);     num_champs=mysql_num_fields(result);     mysql_close(&mysqllocal);      mysql mysqllycee;     mysql_init(&mysqllycee);     if(!mysql_real_connect(&mysqllycee,argv[1],argv[2],argv[3],argv[4],0,null,0))printf("error on second connect");     int i;     while ((row = mysql_fetch_row(result))){         unsigned long *lengths;              lengths = mysql_fetch_lengths(result);         for(i=0;i<num_champs;i++){             if(i==0)sprintf(noparticipant,"%.*s", (int) lengths[i], row[i] ? row[i] : "null");             if(i==1)sprintf(kmparcourus,"%.*s", (int) lengths[i], row[i] ? row[i] : "null");         }            sprintf(requete,"update participants set kmparcourus=%s no_participant=%s",kmparcourus,noparticipant);         if(!mysql_query(&mysqllycee,requete))printf("error on second query");      }     mysql_free_result(result);     mysql_close(&mysqllycee);     return 0; }

i'm working on debian 8, , compiling following command :

gcc updatelycee.c -o updatelycee -lmysqlclient -l/usr/lib64/mysql -i/usr/include/mysql;

edit: added mysql checks, still segfault when starting program.

you close connection local database, , later try fetch rows result set associated connection. not work.

if want transfer data 1 db other must either

  • first slurp wanted data 1 db memory (fetch rows , store contents need in ordinary arrays, instance), or

  • hold connections both databases open @ same time.


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