Segmentation fault problem with mysql_query

[aerobat]

hello all just wondering if anyone can help me with this problem. Ii has to do with a simple mysql_query. i have tried so many different ways of doing it, but it wont work. here is the code:

#include <stdio.h>
#include <math.h>
#include <string.h>
#include <mysql.h>
 
main() {
 
   MYSQL *conn;
   MYSQL_RES *res;
   MYSQL_ROW row;
 
   char *server = "localhost";
   char *user = "root";
   char *password = "********"; /* set me first */
   char *database = "test";
   char airport[5] = "find";
 
   char query[100];
 
    sprintf(query,"SELECT lat,longitude FROM airportslocation WHERE icao = \"%s\"",airport);
 
   conn = mysql_init(NULL);
 
   /* Connect to database */
   if (!mysql_real_connect(conn, server,
         user, password, database, 0, NULL, 0)) {
      fprintf(stderr, "%s\n", mysql_error(conn));
      exit(1);
   }
 
   /* send SQL query */
 
    printf(query);
 
if (mysql_query(conn, query)) {
      fprintf(stderr, "%s\n", mysql_error(conn));
      exit(1);
   }    while ((row = mysql_fetch_row(res)) != NULL)
      printf("%s \n", row[0]);
/* close connection */
   mysql_free_result(res);
   mysql_close(conn);
    return 0;
}
 

Ok no here is the probelm, where i set up the query string i use \" if i remove those it will run, but it will think test is a colum in my database it isnt. i need to put " around it so the sql statement is:

SELECT lat,longitude FROM airportslocatio n WHERE icao = "find"

No if i run it directly it runs fine, like this:

mysql_query(con n, "SELECT lat,longitude FROM airportslocatio n WHERE icao = \"find\"")

it is when i make a string with the query it screws up as you see in my code above, or listed here:

sprintf(query," SELECT lat,longitude FROM airportslocatio n WHERE icao = \"%s\"",airport );

than:

mysql_query(con n, query)

also i tried:

sprintf(query," SELECT lat,longitude FROM airportslocatio n WHERE icao = '%s'",airport);

and that fails as well.

I am running fedorecore 6 and compiling with gcc. any ideas, i am completly stuck.

Shawn F

[sicarie]

Did you ever print out query after the sprintf() statement to see what the string looked like after you stuck it in there?

Also, what error are you getting?

[aerobat]

Did you ever print out query after the sprintf() statement to see what the string looked like after you stuck it in there?

Also, what error are you getting?

I get a segmentation fault then the program aborts. only when i add the \" or '.

I did print out the string query and it contains the correct data which is:

SELECT lat,longitude FROM airportslocatio n WHERE icao ="find"

thanks for the quick reply.....

also if i just send

SELECT lat,longitude FROM airportslocatio n WHERE icao =find

it will get a find colume dosent exist, which is fine since i am looking for find in the colume icao.

so i need the quotes for the call to work correct. Funny thing is I do it with ' in perl and it is fine (i am actually converted parts of a old program)....

[sicarie]

I get a segmentation fault then the program aborts. only when i add the \" or '.

I did print out the string query and it contains the correct data which is:

SELECT lat,longitude FROM airportslocatio n WHERE icao ="find"

thanks for the quick reply.....

also if i just send

SELECT lat,longitude FROM airportslocatio n WHERE icao =find

it will get a find colume dosent exist, which is fine since i am looking for find in the colume icao.

so i need the quotes for the call to work correct. Funny thing is I do it with ' in perl and it is fine (i am actually converted parts of a old program)....

Hmmm. I'm on my work laptop (WinXP, sadly), and just lost my Debian VM, so I can't test a mysql connection, but I'd recommend trying (in lieu of other help) doubly escaping the quotes - \\"%s\\" possibly.

Another idea is to use the apostrophe, though that will probably need to be escaped as well.

Hopefully someone will be able to help you, if not, I am trying to have my linux box back up by tonight. So hopefully (hopefully) I will be able to.

[aerobat]

Hmmm. I'm on my work laptop (WinXP, sadly), and just lost my Debian VM, so I can't test a mysql connection, but I'd recommend trying (in lieu of other help) doubly escaping the quotes - \\"%s\\" possibly.

Another idea is to use the apostrophe, though that will probably need to be escaped as well.

Hopefully someone will be able to help you, if not, I am trying to have my linux box back up by tonight. So hopefully (hopefully) I will be able to.

Yah i tried \' same problem. it has me stumped. It should work, but doesnt. Especially since when i do it direct it works. really wierd. i also tried \\"%s\\" and that gives errors on compile...

[sicarie]

Yah i tried \' same problem. it has me stumped. It should work, but doesnt. Especially since when i do it direct it works. really wierd. i also tried \\"%s\\" and that gives errors on compile...

Well, I'm not surprised that it doesn't work when not direct (I did a bunch of Java SQL stuff recently, and it was the same way), it's just probably one little quirk of the mysql connection that we're missing...

[pongscript]

actual this wont work

SELECT * FROM field="SAMPLE"

but using quote instead of double quote will fix this.


SELECT * FROM field='Sample'


on c++ program try these:

char Query[160];

sprintf(Query," SELECT * From field='%s',"fin d");

then:
mysql_query(mys qlconnection,Qu ery);

just replace mysqlconnection with your connection object;

by the way the error was not on the program but on mysql parsing stuff on the server.. if it can't recognize the query. it will not return a resultset .. so when you try to access a empty result set or a NULL result set it will cause an error since you can't read when nothings there.