C code cant run select query in cron - mysql

Question

We have a C code as below. This is how we have compiled it gcc -o get1Receive $(mysql_config --cflags) get1ReceiveSource.c $(mysql_config --libs) -lrt. I works fine when we run from the terminal. Then we tried to run it using cron job and when we review this two line printf("\nNumf of fields : %d",num_fields); and printf("\nNof of row : %lu",mysql_num_rows(localRes1));. The first line shows 4 as the value and second line never give any values and is always 0. We have took the same select query and run on the db and confirm there is value but it is just not delivering when running via cron job.The script is given executable permission too.
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <stdio.h>
#include <time.h>
#include <signal.h>
#include <mysql.h>
#include <string.h>
int flag = 0;
int main () {
MYSQL *localConn;
MYSQL_RES *localRes1;
MYSQL_ROW localRow1;
char *server = "localhost";
char *user = "user1";
char *password = "*****";
char *database = "test1";
localConn = mysql_init(NULL);
if (!mysql_real_connect(localConn, server,
user, password, database, 0, NULL, 0)) {
fprintf(stderr, "%s\n", mysql_error(localConn));
exit(1);
}
struct timeval tv;
char queryBuf1[500],queryBuf2[500];
char buff1[20] = {0};
char buff2[20] = {0};
gettimeofday (&tv, NULL);
//fprintf (stderr, "[%d.%06d] Flag set to 1 on ", tv.tv_sec, tv.tv_usec);
//tv.tv_sec -= 5;
strftime(buff1, 20, "%Y-%m-%d %H:%M:00", localtime(&tv.tv_sec));
strftime(buff2, 20, "%Y-%m-%d %H:%M:59", localtime(&tv.tv_sec));
printf("\nTime from %s", buff1);
printf("\nTime to %s", buff2);
sprintf(queryBuf1,"SELECT ipDest, macDest,portDest, sum(totalBits) FROM dataReceive WHERE timeStampID between '%s' And '%s' GROUP BY ipDest, macDest, portDest ",buff1,buff2);
printf("\nQuery receive %s",queryBuf1);
if(mysql_query(localConn, queryBuf1))
{
printf("Error in first query of select %s\n",mysql_error(localConn));
exit(1);
}
localRes1 = mysql_store_result(localConn);
int num_fields = mysql_num_fields(localRes1);
printf("\nNumf of fields : %d",num_fields);
printf("\nNof of row : %lu",mysql_num_rows(localRes1));
while((localRow1 = mysql_fetch_row(localRes1)) !=NULL)
{
int totalBits = atoi(localRow1[3]);
printf("totalBits %d\n", totalBits);
printf("RECEIVE %s,%s\n", localRow1[0], localRow1[1]);
if(totalBits>5000)
{
sprintf(queryBuf1,"INSERT INTO alertReceive1 (timeStampID,ipDest, macDest, portDest, totalBits)VALUES ('%s','%s','%s','%s',%s)",buff1, localRow1[0],localRow1[1],localRow1[2],localRow1[3]);
printf("Query 1 before executing %s\n",queryBuf1);
if (mysql_real_query(localConn,queryBuf1,strlen(queryBuf1))) {
printf("Error in first insert %s\n",mysql_error(localConn));
fprintf(stderr, "%s\n", mysql_error(localConn));
exit(1);
}
//printf("Query 1 after executing %s\n",queryBuf1);*/
}
}
mysql_free_result(localRes1);
mysql_close(localConn);
}
We have run this command file get1Receive and resulting to
file get1Receive
get1Receive.c: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.18, not stripped
We have also run this command * * * * * set > /tmp/myvars and below is the results.
GROUPS=()
HOME=/root
HOSTNAME=capture
HOSTTYPE=x86_64
IFS='
'
LOGNAME=root
MACHTYPE=x86_64-redhat-linux-gnu
OPTERR=1
OPTIND=1
OSTYPE=linux-gnu
PATH=/usr/bin:/bin
POSIXLY_CORRECT=y
PPID=11086
PS4='+ '
PWD=/root
SHELL=/bin/sh
SHELLOPTS=braceexpand:hashall:interactive-comments:posix
SHLVL=1
TERM=dumb
UID=0
USER=root
_=/bin/sh

Answer 1

Generic hints (see also my comments):
Take time to read documentation notably from Advanced Linux Programming, man pages (which you can also get by typing man man or man 2 intro on the terminal, etc etc...), and MySQL 5.5 reference. Be sure to understand what GIYF or STFW means.
Put the \n at the end of printf format strings, not the beginning.
Also, call fflush(NULL) if appropriate, notably before any MySQL queries e.g. before your mysql_real_query calls, and at the end of your while loops
Compile with gcc -Wall -g e.g. with the following command in your terminal
gcc -Wall -g $(mysql_config --cflags) get1ReceiveSource.c \
$(mysql_config --libs) -lrt -o get1Receive
Improve the code till no warnings are given. (You may even want to have -Wall -Wextra instead of just -Wall). Don't forget to use a version control system like git.
use the gdb debugger (you need to learn how to use it).
(only once you are sure there is no more bugs in your code replace -g by -O2 -g in your compilation command)
use sizeof; most occurrences of 20 should be a sizeof, or at the very least use #define SMALLSIZE 20 and then only SMALLSIZE not 20.
Use snprintf not sprintf (and test its result size, which should fit!). snprintf(3) takes an extra size argument, e.g.
if (snprintf(querybuf, sizeof querybuf,
"SELECT ipDest, macDest, portDest, sum(totalBits)"
" FROM dataReceive"
" WHERE timeStampID between '%s' And '%s' "
" GROUP BY ipDest, macDest, portDest ",
buff1, buff2) >= (int) (sizeof querybuf))
abort();
consider using syslog(3) with openlog, and look into your system logs.
I don't see how is queryBuf1 declared. (Your code, as posted, probably don't even compile!). You might want something like char querybuf[512]; ...
And most importantly, calling mysql_real_query inside a mysql_fetch_row loop is wrong: you should have fetched all the rows before issuing the next MySQL query. Read more about MySQL C API.
You also forgot to test the result localRes1 of mysql_store_result(localConn); show somehow (perhaps thru syslog) the mysql_error(localConn) when localRes1 is NULL ....