One SQL and C question

[QQ]

In C and SQL I write a very simple program and it works
However when I try to create a MYSQL object and call it in the
function,
it fails. Here is my program, what's wrong? Thanks a lot!

#include <stdlib.h>
#include <stdio.h>
#include "mysql.h"
int main(int argc, char *argv[]) {
MYSQL my_connection;
mysql_init(&my_connection);
if (mysql_real_connect(&my_connection, "localhost", "","", "",
0, NULL, 0))
{
printf("Connection success\n");
db_Roamer_Create("testtest");
}
else
{
fprintf(stderr, "Connection failed\n");
if (mysql_errno(&my_connection))
{
fprintf(stderr, "Connection error %d: %s\n",
mysql_errno(&my_connection), mysql_error(&my_connection));
}
}
mysql_close(&my_connection);

}

int db_Roamer_Create(MYSQL *my_connection,const char *dbname)
{
printf("dbName is %s\n",dbname);
char *cmd;
if ( ( cmd = malloc( strlen( "CREATE DATABASE " ) +
strlen( dbname ) + 1 ) ) == NULL ) {
fprintf( stderr, "Running out of memory!\n" );
exit( EXIT_FAILURE );
}
sprintf(cmd,"CREATE DATABASE %s;",dbname);

if(mysql_query(my_connection,cmd)==0)
{
printf("Create Database sucessfully");
}
else
{
fprintf(stderr, "Create Database failed\n");
if (mysql_errno(my_connection)) {
fprintf(stderr, "Create Database error %d: %s\n",
mysql_errno(my_connection), mysql_error(my_connection));
}
}
}

 

[SM Ryan]

# int db_Roamer_Create(MYSQL *my_connection,const char *dbname)
# {
# printf("dbName is %s\n",dbname);
# char *cmd;
# if ( ( cmd = malloc( strlen( "CREATE DATABASE " ) +
# strlen( dbname ) + 1 ) ) == NULL ) {
# fprintf( stderr, "Running out of memory!\n" );
# exit( EXIT_FAILURE );
# }
# sprintf(cmd,"CREATE DATABASE %s;",dbname);

(1) Your malloc is one character short. You need +1 for the ";" and +1 for the
string terminator. My way of doing this would be
static char F[] = "CREATE DATABASE %s;";
char *f = malloc(sizeof F + strlen(dbname));
sprintf(f,F,dbname);

(2) HOWEVER--Don't include the ';' terminator. That's an artifact of marking
the end of the command when read from a terminal. You don't use it when you
call mysql_query.

 

[poison.summer]

Thanks a lot

However, my program works if I define MYSQL my_connection
to be a global variable.

Any reason for that?

 

[Gordon Burditt]

In C and SQL I write a very simple program and it works

However when I try to create a MYSQL object and call it in the
function,
it fails.

There is no place in your program where it can print "it fails".
*HOW* does it fail? You deserve to have it fail in mysql_real_connect()
for not putting a password on your database, even if it is accessible
only to localhost. You are also obviously out of disk space.

You call db_Roamer_Create with *one* argument, yet define it with
two. Why? Didn't your compiler warn you about that?

Here is my program, what's wrong? Thanks a lot!

#include <stdlib.h>
#include <stdio.h>
#include "mysql.h"
int main(int argc, char *argv[]) {
MYSQL my_connection;
mysql_init(&my_connection);
if (mysql_real_connect(&my_connection, "localhost", "","", "",
0, NULL, 0))
{
printf("Connection success\n");
db_Roamer_Create("testtest");
}
else
{
fprintf(stderr, "Connection failed\n");
if (mysql_errno(&my_connection))
{
fprintf(stderr, "Connection error %d: %s\n",
mysql_errno(&my_connection), mysql_error(&my_connection));
}
}
mysql_close(&my_connection);

}

int db_Roamer_Create(MYSQL *my_connection,const char *dbname)
{
printf("dbName is %s\n",dbname);
char *cmd;
if ( ( cmd = malloc( strlen( "CREATE DATABASE " ) +
strlen( dbname ) + 1 ) ) == NULL ) {

You malloc() insufficient memory here for what you want to put in it.

 

[SM Ryan]

(e-mail address removed) wrote:
# Thanks a lot
#
# However, my program works if I define MYSQL my_connection
# to be a global variable.

Are you passing in the value if it's a parameter?

 

[QQ]

No
if I pass it as a parameter
it fails,

if I define it as a global
it works

feell weired

 

[Keith Thompson]

No
if I pass it as a parameter
it fails,

if I define it as a global
it works

feell weired

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