There is something weird when executing popen on Linux. So basically in a much bigger application I have a function called execute that runs a command by using popen and returns its stdout output.
#define CMD "some_command -s" // This is the command
#define MAX_BUF 1024*6
static std::string execute(const char* cmd) {
std::string result;
char buffer[MAX_BUF];
FILE* pipe = popen(cmd, "r");
if(!pipe)
throw -1;
try{
while(!feof(pipe)){
if(fgets(buffer, MAX_BUF, pipe) != NULL)
result += buffer;
}
}catch(...){
pclose(pipe);
throw;
}
pclose(pipe);
return result;
}
This usually works fine, the problem comes when rebooting the system. If the applications runs as a daemon for a service, if this service is run at boot time the size of the result variable is 0. When doing a service name_of_service restart, which kills and relaunches the application, then it works and the result variable size is the expected one.
Also tried executing system("some_command -s > /tmp/command_out"); before running the popen and the file /tmp/command_out had the expected output. So this is not a race condition in which the some_command dependencies have not been initialized.
UPDATE
Running the command on another terminal at the same time also works. And inside the service, If I change some_command -s for other commands like ls /tmp, then popen does result in some output.
