How to execute some shell script after opencv detect circle - c++

Question

How to execute some shell script (e.g 1.sh) after opencv detect circle?
I have used exec, it works but opencv program close after circle detected, and what I want is that the program didn't close until I press "q" key.
Here is my code:
#include<cv.h>
#include<highgui.h>
#include <math.h>
#include <stdlib.h>
#include <unistd.h>
using namespace std;
int main( int argc, char **argv )
{
CvCapture *capture = 0;
IplImage *img = 0;
int key = 0;
CvFont font;
cvInitFont(&font, CV_FONT_HERSHEY_PLAIN,1.0,1.0,0,1,CV_AA);
capture = cvCaptureFromCAM( 0 );
if ( !capture ) {
fprintf( stderr, "Cannot open initialize webcam!\n" );
return 1;
}
cvNamedWindow( "result", CV_WINDOW_AUTOSIZE );
img = cvQueryFrame( capture );
if (!img)
exit(1);
IplImage* gray = cvCreateImage( cvGetSize(img), 8, 1 );
CvMemStorage* storage = cvCreateMemStorage(0);
while( key != 'q' ) {
img = cvQueryFrame( capture );
if( !img ) break;
cvCvtColor( img, gray, CV_BGR2GRAY );
cvSmooth( gray, gray, CV_GAUSSIAN, 5, 5 );
CvSeq* circles = cvHoughCircles( gray, storage, CV_HOUGH_GRADIENT, 2, >gray->height/40, 200, 100/*, 20, 100*/ );
int i;
for( i = 0; i < circles->total; i++ )
{
float* p = (float*)cvGetSeqElem( circles, i );
cvCircle( img, cvPoint(cvRound(p[0]),cvRound(p[1])), cvRound(p[2]), >CV_RGB(50,255,30), 5, 8, 0 );
cvPutText(img, "CIRCLE",cvPoint(cvRound(p[0]+45),cvRound(p[1]+45)), &font, >CV_RGB(50,10,255));
if ( circles ) {
execl("./1.sh", (char *)0);
}
}
cvShowImage( "result", img );
cvShowImage("gray", gray);
key = cvWaitKey( 1 );
}
// cvReleaseMemStorage(storage);
// cvReleaseImage(gray);
cvDestroyAllWindows();
cvDestroyWindow( "result" );
cvReleaseCapture( &capture );
return 0;
}
I used codeblocks on ubuntu.

Answer 1

After exec*, none of the code (in that process) will be reached. You can fork, exec if you want the program to continue without waiting for the script to complete, otherwise add a wait. Alternatively, you could use system or popen.
Examples:
example function to fork a command and wait:
#include <unistd.h>
/*as a macro*/
#define FORK_EXEC_WAIT(a) ({int s,p;if((p=fork())==0) \
{execvp(a[0],a);}else{while(wait(&s)!= p);}})
/*as a function*/
void fork_exec_wait(char** a) {
int s,p;
if((p=fork())==0){
execvp(a[0],a);
}else{
while(wait(&s)!= p);
}
}
to fork a command and continue
#include <unistd.h>
/*as a macro*/
#define FORK_EXEC(a) ({if((fork())==0) execvp(a[0],a);})
/*as a function*/
void fork_exec(char** a) {
int s,p;
if((p=fork())==0)
execvp(a[0],a);
}
the system command is ~ fork-exec-wait of "sh -c command args"
#include <stdlib.h>
system("command args");
the popen command is similar without the sh -c and will give you the output as a stream (think pipes, fifo, etc)
#include <stdio.h>
FILE *fp;
fp = popen("command args", "r");
...
pclose(fp);