The sqldetach() function

1. Call fork() from the parent process to create a copy of the parent process (the child process). Now both parent and child share the same connection to the database server.
2. Call sqldetach() from the child process to detach the child process from the database server. This call closes the connection in the child process.

/*
   * sqldetach.ec *

   This program demonstrates how to detach a child process from a
   parent process using the ESQL/C sqldetach() library function.
*/

main()
{
    EXEC SQL BEGIN DECLARE SECTION;
        mint pa;
    EXEC SQL END DECLARE SECTION;

    printf("SQLDETACH Sample ESQL Program running.\n\n");

    printf("Beginning execution of parent process.\n\n");
    printf("Connecting to default server...\n");
    EXEC SQL connect to default;
    chk("CONNECT");
    printf("\n");

    printf("Creating database 'aa'...\n");
    EXEC SQL create database aa;
    chk("CREATE DATABASE");
    printf("\n");

    printf("Creating table 'tab1'...\n");
    EXEC SQL create table tab1 (a integer);
    chk("CREATE TABLE");
    printf("\n");

    printf("Inserting 4 rows into 'tab1'...\n");
    EXEC SQL insert into tab1 values (1);
    chk("INSERT #1");
    EXEC SQL insert into tab1 values (2);
    chk("INSERT #2");
    EXEC SQL insert into tab1 values (3);
    chk("INSERT #3");
    EXEC SQL insert into tab1 values (4);
    chk("INSERT #4");
    printf("\n");

    printf("Selecting rows from 'tab1' table...\n");
    EXEC SQL declare c cursor for select * from tab1;
    chk("DECLARE");

EXEC SQL open c;
    chk("OPEN");

    printf("\nForking child process...\n");
    fork_child();

    printf("\nFetching row from cursor 'c'...\n"); 
    EXEC SQL fetch c into $pa;
    chk("Parent FETCH");
    if (sqlca.sqlcode == 0)
        printf("Value selected from 'c' = %d.\n", pa); 
    printf("\n");

    printf("Cleaning up...\n");
    EXEC SQL close database;
    chk("CLOSE DATABASE");
    EXEC SQL drop database aa;
    chk("DROP DATABASE");
    EXEC SQL disconnect all;
    chk("DISCONNECT");

    printf("\nEnding execution of parent process.\n");
    printf("\nSQLDETACH Sample Program over.\n\n");
}

fork_child()
{
    mint rc, status, pid;

    EXEC SQL BEGIN DECLARE SECTION;
        mint cnt, ca;
    EXEC SQL END DECLARE SECTION;

    pid = fork();
    if (pid < 0)
        printf("can't fork child.\n");

    else if (pid == 0)
   {
        printf("\n**********************************************\n");
        printf("* Beginning execution of child process.\n");
        rc = sqldetach();
        printf("* sqldetach() call returns %d.\n", rc);

        /* Verify that the child is not longer using the parent's
         * connection and has not inherited the parent's connection
         * environment.
         */
        printf("* Trying to fetch row from cursor 'c'...\n"); 
        EXEC SQL fetch c into $ca;
        chk("* Child FETCH");
        if (sqlca.sqlcode == 0)
            printf("* Value from 'c' = %d.\n", ca); 

        /* startup a connection for the child, since
         * it doesn't have one.
         */
      printf("\n* Establish a connection, since child doesn't have one\n");
        printf("* Connecting to database 'aa'...\n");
        EXEC SQL connect to 'aa';
        chk("* CONNECT");
        printf("* \n");
      printf("* Determining number of rows in 'tab1'...\n");
        EXEC SQL select count(*) into $cnt from tab1;
        chk("* SELECT");
        if (sqlca.sqlcode == 0)
            printf("* Number of entries in 'tab1' =  %d.\n", cnt);
        printf("* \n");

        printf("* Disconnecting from 'aa' database...\n");
        EXEC SQL disconnect current;
        chk("* DISCONNECT");
        printf("* \n");
        printf("* Ending execution of child process.\n");
        printf("**********************************************\n");

        exit();
   }

    /* wait for child process to finish */
    while ((rc = wait(&status)) != pid && rc != -1);

}

chk(s)
char *s;
{
    mint msglen;
    char buf1[200], buf2[200];

    if (SQLCODE == 0)
   {
        printf("%s was successful\n", s);
        return;
   }
    printf("\n%s:\n", s);
    if (SQLCODE)
   {
        printf("\tSQLCODE =  %6d: ", SQLCODE);
        rgetlmsg(SQLCODE, buf1, sizeof(buf1), &msglen);
        sprintf(buf2, buf1, sqlca.sqlerrm);
        printf(buf2);
        if (sqlca.sqlerrd[1])
       {
            printf("\tISAM Error =  %6hd: ", sqlca.sqlerrd[1]);
            rgetlmsg(sqlca.sqlerrd[1], buf1, sizeof(buf1), &msglen);
            sprintf(buf2, buf1, sqlca.sqlerrm);
            printf(buf2);
       }
   }
}