Popen导致程序死机

Question

I have a function that returns the strength of my Wifi signal on a certain interval.

FILE *sig;
int sigstr=0, max;
sig = popen("iwconfig wlan0 | awk '/Link/ {print $2}'","r");
while(fgetc(sig)!='=');
fscanf(sig,"%d/%d", &sigstr, &max);
pclose(sig);
return(((sigstr*4)+(max/2))/max);

The problem I am running into is that my program freezes up after a period of time depending on how long the interval is for getting the Wifi signal. The shorter the interval the faster my program freezes. Now correct me if I am wrong but this seems to be a problem with memory. Where as time progresses some item(s) are not properly removed from the stack or deallocated, leading to memory being filled up and eventually reaching a level where the program can not continue to run. So my question is apart from what I have up top do I need to include another statement to free file sig or does pclose take care of that?

Thanks!

Answer 1

Its because fscanf can block. Set your file descriptor obtained from popen to nonblocking using fcntl.