I am trying to re-direct standard output from a Process, but I want to re-direct line by line as the other process outputs rather than all at once. Right now my code looks like this:
proc->StartInfo->FileName = "ping.exe";
proc->StartInfo->UseShellExecute = false;
proc->StartInfo->RedirectStandardOutput = true;
proc->StartInfo->Arguments = "-n 1 www.google.com";
proc->Start();
StreamReader^ stream = proc->StandardOutput;
if(stream){
//String^ s = stream->ReadToEnd();
//Console::WriteLine(s);
proc->WaitForExit();
while(stream->Peek() >= 0)
{
Console::WriteLine(stream->ReadLine());
}
}
But what it has to do is wait for the process to exit before printing all of the Ping output. If you run ping natively, you can see that the output comes periodically as the HTTP requests are made. I basically want the output to be queued up and re-directed the same way, line by line.
Got it:
String^ s;
//Console::WriteLine(s);
//proc->WaitForExit();
while(s=stream->ReadLine())
{
Console::WriteLine(s);
}
This works
Related
I am testing application's latency during UDP communication on windows 10.
I tried to send a message every 1 second and receive a response sent immediately from the remote.
Send thread
It works every 1 second.
auto start = std::chrono::system_clock::now();
unsigned int count = 1;
while (destroyFlag.load(std::memory_order_acquire) == false)
{
if (isReady() == false)
{
break;
}
/*to do*/
worker_();
std::this_thread::sleep_until(start + std::chrono::milliseconds(interval_)* count++);
}
worker_()
Send thread call this. just send message and make log string.
socket_.send(address_);
logger_.log("," + std::string("Send") + "\n");
Receiver
When message arrives, it creates a receive log string and flushes it to a file.
auto& queueData = socket_.getQueue();
while (queueData.size() > 0)
{
auto str = queueData.dequeue();
logger_.log(",Receive" + str + "\n");
logger_.flush();
}
I've been testing it overnight and I can't figure out why I got this result.
chart for microseconds
x-axis : Hour_Minute_second
y-axis : microseconds
For a few hours it seemed to work as expected. But after that, the time gradually changed and went to a different time zone.
Does anyone know why this is happening?
std::chrono::steady_clock is working.
It made my charts straight.
And another way, turn off the windows automatically time synchronize.
I developed a little application that read data from a sensor, store them in SPIFFS memory of my wemos D1 mini (esp8266) and then create a JSON Document and send it via MQTT to my topic. The problem is that as long as I send a JSON Doc with 10 object everything works great, but when I increase the size of the doc over 10 object nothing works. Eventually I need to send a JSON doc with 100 object inside.
What have I already done?
I'm using PubSubClient and I already set the MAX_PACKET_SIZE to the correct value
Using arduinojson assistant I found out the size of my JSON Document (8192 bytes)
I tried to use mqtt.fx to test if the problem was the esp8266 or the mqtt broker. Using mqtt.fx I'm able to send a JSON doc with 100 objects
As soon as I increase the size of the JSON doc I get a wdt error from the serial monitor of my arduino IDE.
I search the internet for wdt error but I don't get what they are and how to solve my problem
Last things I already tried to show on the serial monitor the file.txt in the SPIFFS where I store the data and I can store and then read the 100 object
So in the end I think it's an esp8266 problem and not PubSubClient or MQTT. Am I right?
Does anyone of you here ever encountered this problem before or have some other test I can run?
I search the internet for wdt error but I don't get what they are and how to solve my problem
WDT stands for a Watch Dog Timer. https://os.mbed.com/cookbook/WatchDog-Timer#:~:text=A%20watchdog%20timer%20(WDT)%20is,a%20software%20or%20hardware%20fault.
A watchdog timer (WDT) is a hardware timer that automatically generates a system reset if the main program neglects to periodically service it. It is often used to automatically reset an embedded device that hangs because of a software or hardware fault. Some systems may also refer to it as a computer operating properly (COP) timer. Many microcontrollers including the mbed processor have watchdog timer hardware.
Let's paint a better picture with an example. Let's say that you setup a WDT with a time of 10 seconds. Then the WDT starts counting down from 10 seconds. If it reaches 0 the processor will reset. "Feeding" the WDT will reset the countdown to the original value in this case 10 seconds. So if the WDT has counted down to 4 seconds remaining and you feed it, it resets the countdown back to 10 and starts counting down again.
Does anyone of you here ever encountered this problem before or have some other test I can run?
It looks to me like sending a larger JSON object takes a longer period of time than what the WDT is set for. One possibility would be to break up the JSON object into multiple pieces and send it in smaller chunks instead of one large one. This way the time between WDT "feedings" is reduced. I have no idea if this would be possible for you to change. But this should at least give you a better idea of what's happening.
OK in the end the problem was that sending a large JsonDocument triggered the WDT and the only way I found to overcome this problem was, as suggested by adamvz, to create a main file with all the 100 object, then call a function to split that file in 10 smaller one and send each of them over the internet through an HTTP request or Mosquitto.
Supposing you already created the main file in the spiffs memory, then:
This to split the main file:
void WritePacks() {
sourceFile = LittleFS.open("/file.txt", "r");
if (!sourceFile) {
Serial.println(F("Error: file.txt open failed"));
} else {
Serial.println("File open w/ success");
for (byte idx = 0; idx < outputCount; idx++) {
String aLine;
aLine.reserve(capacity);
if (sourceFile.available() == 0) break;
destinationFile = LittleFS.open(outputFileNames[idx], "w");
if (!destinationFile) {
Serial.print(F("can't open destination "));
Serial.println(outputFileNames[idx]);
break;
} else {
int lineCount = 0;
while (sourceFile.available() && (lineCount <= 10)) {
aLine = sourceFile.readStringUntil('\n');
destinationFile.println(aLine); // double check if the '\n' is in the String or not (--> print or println accordingly)
lineCount++;
}
outputIndex = idx;
Serial.println(outputIndex);
destinationFile.close();
}
} // end for
sourceFile.close();
}
}//end WritePacks
This to publish:
//------ HTTP Publish ------
void httpPublish(){
const char * outputFileNames[] = {"/out1.txt", "/out2.txt", "/out3.txt", "/out4.txt", "/out5.txt", "/out6.txt", "/out7.txt", "/out8.txt", "/out9.txt", "/out10.txt"};
const byte outputCount = sizeof outputFileNames / sizeof outputFileNames[0];
byte outputIndex = 0;
File sourceFile;
File destinationFile;
//Serial.println(capacity);
for (byte idx = 0; idx < outputCount; idx++) {
DynamicJsonDocument doc(capacity);
DynamicJsonDocument globalDoc(capacity);
StaticJsonDocument <1024> localDoc;
String aLine;
aLine.reserve(capacity);
destinationFile = LittleFS.open(outputFileNames[idx], "r");
if (!destinationFile) {
Serial.print(F("can't open destination "));
Serial.println(outputFileNames[idx]);
break;
} else {
Serial.print("Reading: ");
Serial.println(outputFileNames[idx]);
//int lineCount = 0;
while (destinationFile.available()) {
aLine = destinationFile.readStringUntil('\n');
DeserializationError error = deserializeJson(localDoc, aLine);
if (!error) globalDoc.add(localDoc);
else{ Serial.println("Error Writing All files");}
}//while
JsonObject Info = doc.createNestedObject("Info");
Info["Battery"] = battery;
Info["ID"] = id;
Info["Latitudine"] = latitudine;
Info["Longitudine"] = longitudine;
JsonArray Data = doc.createNestedArray("Data");
Data.add(globalDoc);
HTTPClient http;
//Send request
http.begin("yourURL");
char buffer[capacity];
size_t n = serializeJson(doc, buffer);
http.POST(buffer);
Serial.println(buffer);
http.end();
destinationFile.close();
}
}// end for
}//end httpPublish
I have to get the output of a QProcess while it is running. Therefore I have written the following Code:
CommandExecutor_C::CommandExecutor_C():
mProcessStatus(AI_UNKNOWN),
mOnTdiActiveCallback(),
mTdiProcess(new QProcess)
{
connect(mTdiProcess, SIGNAL(readyReadStandardOutput()), this, SLOT(CheckOutput()));
connect(mTdiProcess, SIGNAL(readyReadStandardError()), this, SLOT(CheckOutput()));
}
void CommandExecutor_C::ExecuteCommand(QString &aCommand)
{
mTdiProcess->start(aCommand, QProcess::Unbuffered | QProcess::ReadWrite);
LOGINFO(FB_TDI,"Launch command: " + aCommand.toStdString());
}
void CommandExecutor_C::CheckOutput()
{
QString StdOut = QString(mTdiProcess->readAllStandardOutput());
QString StdErr = QString(mTdiProcess->readAllStandardError());
mProcessStatus = CheckTdiAutomationInterface(StdOut.toStdString(), StdErr.toStdString());
if(mProcessStatus != AI_UNKNOWN)
{
OnTdiActive(mProcessStatus);
}
}
This works fine if QProcess gets finished but in my case the Process starts an automation interface which should run in background permanently. Therefore I have used "readyReadStandardOutput" and connect it to the slot CheckOutput(). CheckOutput() is getting called just if the process has been finished. Otherwise I am waiting endless.
I have googled a lot about the problem but nothing worked. I am very sure that the output is getting buffered and does just return if the Process has finished. Therefore I have started the Process in Unbuffered-Mode. I have also tried to forward the channels of mTdiProcess. Here the Code:
void CommandExecutor_C::ExecuteCommand(QString &aCommand)
{
mTdiProcess->setProcessChannelMode(QProcess::ForwardedChannels);
mTdiProcess->start(aCommand, QProcess::Unbuffered | QProcess::ReadWrite);
LOGINFO(FB_TDI,"Launch command: " + aCommand.toStdString());
}
But nothing worked. I hope you can help me.
I am using Qt 5.4.2 if that's important.
I usually check the output in regular intervals like this:
bool returnBool = false;
while (returnBool == false)
{
/*! Wait one second if the process finishes. Then read all output to
* stdout and stderr and redo. */
returnBool = process.waitForFinished(1000);
QString outputStdOut = process.readAllStandardOutput();
QString outputStdErr = process.readAllStandardError();
}
I want to get a Linux command's output string as well as command output status in a C++ program. I am executing Linux commands in my application.
for example:
Command:
rmdir abcd
Command output string:
rmdir: failed to remove `abcd': No such file or directory
Command Status:
1 (Which means command has been failed)
I tried using Linux function system() which gives the output status, and function popen() which gives me output string of a command, but neither function gives me both
the output string and output status of a Linux command.
The output string is in standard output or standard error descriptor (1 or 2, respectively).
You have to redirect these streams (take a look at dup and dup2 function) to a place, where you can read them (for example - a POSIX pipe).
In C I'd do something like this:
int pd[2];
int retValue;
char buffer[MAXBUF] = {0};
pipe(pd);
dup2(pd[1],1);
retValue = system("your command");
read(pd[0], buffer, MAXBUF);
Now, you have (a part of) your output in buffer and the return code in retValue.
Alternatively, you can use a function from exec (i.e. execve) and get the return value with wait or waitpid.
Update: this will redirect only standard output. To redirect standard error, use dup2(pd[1],1).
The simplest solution is to use system, and to redirect standard out and standard error to a temporarly file, which you can delete later.
Unfortunately there's no easy and simple way in C on Linux to do this. Here's an example how to read/write stdout/stderr/stdin of child process correctly.
And when you want to receive exit code you have to use waitpid (complete example is provided on the bottom of the provided page):
endID = waitpid(childID, &status, WNOHANG|WUNTRACED);
Now you just have to join those two together :)
There's also a great free book named Advanced Linux Programming (ALP) containing detailed information about these kinds of problem available here.
Building on Piotr Zierhoffer answer above, here's a function that does just that, and also restores stdout and stderr their original state.
// Execute command <cmd>, put its output (stdout and stderr) in <output>,
// and return its status
int exec_command(string& cmd, string& output) {
// Save original stdout and stderr to enable restoring
int org_stdout = dup(1);
int org_stderr = dup(2);
int pd[2];
pipe(pd);
// Make the read-end of the pipe non blocking, so if the command being
// executed has no output the read() call won't get stuck
int flags = fcntl(pd[0], F_GETFL);
flags |= O_NONBLOCK;
if(fcntl(pd[0], F_SETFL, flags) == -1) {
throw string("fcntl() failed");
}
// Redirect stdout and stderr to the write-end of the pipe
dup2(pd[1], 1);
dup2(pd[1], 2);
int status = system(cmd.c_str());
int buf_size = 1000;
char buf[buf_size];
// Read from read-end of the pipe
long num_bytes = read(pd[0], buf, buf_size);
if(num_bytes > 0) {
output.clear();
output.append(buf, num_bytes);
}
// Restore stdout and stderr and release the org* descriptors
dup2(org_stdout, 1);
dup2(org_stderr, 2);
close(org_stdout);
close(org_stderr);
return status;
}
you can use popen system call, it will redirect output to a file and from file you can redirect output to a string. like :
char buffer[MAXBUF] = {0};
FILE *fd = popen("openssl version -v", "r");
if (NULL == fd)
{
printf("Error in popen");
return;
}
fread(buffer, MAXBUF, 1, fd);
printf("%s",buffer);
pclose(fd);
For more information read man page for popen.
I'm using Winsock to send commands through Telnet ; but for some reason when I try to send a string, a few characters get dropped occasionally. I use send:
int SendData(const string & text)
{
send(hSocket,text.c_str(),static_cast<int>(text.size()),0);
Sleep(100);
send(hSocket,"\r",1,0);
Sleep(100);
return 0;
}
Any suggestions?
Update:
I checked and the error still occurs even if all the characters are sent. So I decided to change the Send function so that it sends individual characters and checks if they have been sent:
void SafeSend(const string &text)
{
char char_text[1];
for(size_t i = 0; i <text.size(); ++i)
{
char_text[0] = text[i];
while(send(hSocket,char_text,1,0) != 1);
}
}
Also, it drops characters in a peculiar way ; i.e. in the middle of the sentence. E.g.
set variable [fp]exit_flag = true
is sent as
ariable [fp]exit_flag = true
Or
set variable [fp]app_flag = true
is sent as
setrable [fp]app_flag = true
As mentioned in the comments you absolutely need to check the return value of send as it can return after sending only a part of your buffer.
You nearly always want to call send in a loop similar to the following (not tested as I don't have a Windows development environment available at the moment):
bool SendString(const std::string& text) {
int remaining = text.length();
const char* buf = text.data();
while (remaining > 0) {
int sent = send(hSocket, buf, remaining, 0);
if (sent == SOCKET_ERROR) {
/* Error occurred check WSAGetLastError() */
return false;
}
remaining -= sent;
buf += sent;
}
return true;
}
Update:
This is not relevant for the OP, but calls to recv should also structured in the same way as above.
To debug the problem further, Wireshark (or equivalent software) is excellent in tracking down the source of the problem.
Filter the packets you want to look at (it has lots of options) and check if they include what you think they include.
Also note that telnet is a protocol with numerous RFCs. Most of the time you can get away with just sending raw text, but it's not really guaranteed to work.
You mention that the windows telnet client sends different bytes from you, capture a minimal sequence from both clients and compare them. Use the RFCs to figure out what the other client does different and why. You can use "View -> Packet Bytes" to bring up the data of the packet and can easily inspect and copy/paste the hex dump.