I follow the \"button test \" source code given by ken,however I pushed several times to change the value of \"numclicks\",the I find one place maybe wrong,I changed some codeS in it as follow:
while (read (fd, buf, 1) != 0) {
if (buf[0] == \'1\') {
numclicks += 1;
printf (\"The button has been pushed %d times.
\\n\", numclicks);
}
}
It\'s still takes several pushes to make \"numclicks\" increased by one.I don\'t know what\'s the matter.
code given by ken:
# include <stdio.h># include <unistd.h># include <fcntl.h># include <stdlib.h>
/* open /dev/button device for blocked reading
* whenever button is pressed,
* display number of times button was pressed since startup
*/
int
main (int argc, char* argv[])
{
int fd;
char path[] = \"/dev/button\";
int numclicks = 0;
char buf[1];
fd = open (path, O_RDONLY);
if (fd < 0) {
/* error occurred */
perror (\"open\");
exit (EXIT_FAILURE);
} else {
printf (\"opened %s
\\n\", path);
}
/* file is now open for reading... do your stuff... */
while (read (fd, buf, 1) != 0) {
if (buf[0] == \'1\') {
numclicks += 1;
}
printf (\"The button has been pushed %d times.
\\n\", numclicks);
}
if (close (fd) < 0) {
perror (\"close\");
exit (EXIT_FAILURE);
} else {
printf (\"closed %s
\\n\", path);
}
exit (EXIT_SUCCESS);
}
