I was wondering if you could have it so when you go and click on a program in linux it always automatically brings up the command line for the information being displayed or if I decided to use ncurses for an interface. If so is this a system specific call or can you do this with ncurses? Because half of my program is going to be via terminal.
Thanks
Since nitt wouldn't let me amend his code snippet, I'm posting a corrected snippet in case anyone would like to use it:
#include <cstdio>
#include <unistd.h>
#include <iostream>
int main(int argc, char* argv[])
{
if (isatty(0))
{
std::cout << "Hello, World!" << std::endl;
for (int i=0; i<argc; i++)
std::cout << "arg: " << i << "\t" << argv[i] << std::endl;
std::cout << "Press return to continue . . ." << std::flush;
std::cin.get();
}
else
{
const char* args[argc+3], **it=args;
*it++ = "gnome-terminal";
*it++ = "-x";
it = std::copy(argv, argv+argc, it);
*it++ = 0;
if (-1 == execvp("gnome-terminal", (char* const*) &args[0]))
perror("exec");
}
}
Yes, just invoke a terminal with your app in it. For example:
rxvt -e myapp
Starts a terminal running your app. You could also use xterm. If you want to use wide chars/unicode I recommend rxvt-unicode.
You can put this in a .desktop file with an icon defined there, and then that will be placed in the system menu.
#include <stdlib.h>
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int fileExists(string x321) {
ifstream x123 (x321.c_str());
string x213;
x123 >> x213;
if (x213 == "") {
return false;
} else {
return true;
}
}
int createConsole(string fname) {
if (fileExists("~tmp") == false) {
ofstream tmp ("~tmp");
tmp << "tmpfile";
fname = "gnome-terminal -e " + fname;
system(fname.c_str());
system("exit");
return 0;
}
remove("~tmp");
return 1;
}
int main(int argc, char** args) {
createConsole(args[0]);
cout << "Hello, World!" << endl;
cout << "Press return to continue . . .";
cin.get();
}
Pay attention to the "createConsole" and "fileExists" function. I wrote this myself.
Related
I tried programming a file writer, but when i try to write to a file with something that has multiple words it will suddenly create files.
My code
#include <fstream>
#include <iostream>
#include <unistd.h>
int main(int argc, char *argv[]) {
char cwd[256];
while (true) {
getcwd(cwd, 256);
std::string cwd_s = (std::string)cwd;
std::string Input;
std::cout << cwd_s << "> ";
std::cin >> Input;
std::ofstream file(Input);
std::cout << "cmd /";
std::cin >> Input;
file << Input;
};
for (int i; i < argc; i++) {
std::cout << argv[i] << '\n';
};
return 0;
}
I expected to get this:
C:\Users\code> File.txt
cmd /hello world!
File.txt
hello world!
But it only had "hello", it created another file named world!
I have tried changing the code, but to no avail.
So I have wrote this code that I think does what you expect. The behavior you were seing is because you used the same string to store the filename and the user input. Also you redefined a new file every loop (without closing the previous one). I added a signal handler since if you press Ctrl+C the program would quit without saving/closing the file.
I added comments about how you can make a better CLI interface (if you're interested)
#include <iostream>
#include <fstream>
#include <string>
#include <unistd.h>
std::ofstream outfile;
void signalHandler(int signum) {
outfile.close();
exit(signum);
}
int main() {
char cwd[256];
if (getcwd(cwd, sizeof(cwd)) != NULL) {
std::cout << cwd << "> ";
} else {
std::cerr << "Error: Could not get current working directory." << std::endl;
return 1;
}
std::string filename;
std::getline(std::cin, filename);
outfile.open(filename);
// We intercept the Ctrl+C signal to close the file before exiting. Else nothing will be written to it.
// You can also use Ctrl+D (EOF: End Of File) to exit the program.
// The best praticte would be to implement a command line interface with a "quit" command. (like a map<string, function> for example)
signal(SIGINT, signalHandler);
// Another good practice is to check if the file did open correctly.
if (!outfile.is_open()) {
std::cerr << "Error: Could not open file for writing." << std::endl;
return 1;
}
std::cout << "cmd / ";
char ch;
while (std::cin.get(ch)) {
outfile.put(ch);
if (ch == '\n') {
std::cout << "cmd / ";
}
}
outfile.close();
return 0;
}
Hope it will help you ! And if you have any question about the code feel free to ask I'll explain !
I've been trying to write a code to read from a file line by line:
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
ifstream jin("Story.txt");
// ins.open("Story.txt", ios::in);
if (!jin)
{
cout << "File not opened" << endl;
return 1;
}
else{
char a[100];
do
{
jin.getline(a, 100);
cout << a << endl;
}
while (!jin.eof());
jin.close();
return 0;
}
}
However, on executing this program on Visual Studio Code on Windows, it behaves as infinite loop.
Can someone tell what's wrong?
(I am sure that the file Story.txt exists, no doubt about that)
When std::istream::getline has read 100-1 characters (without finding a newline,\n), it will set the failbit on the stream. This prevents further reading on the stream (unless you reset that state). It does however not set eofbit so you are now in a bit of a pickle. The failbit prevents further reading, and eof() returns false, because eofbit is not set - it will therefore loop indefinitely.
If at least one of the lines in Story.txt is longer than 99 chars, the above is what will happen.
The easiest way out is to use a std::string and std::getline instead:
#include <cerrno>
#include <cstring>
#include <fstream>
#include <iostream>
#include <string>
int main() {
std::ifstream jin("Story.txt");
if(!jin) {
std::cerr << "File not opened: " << std::strerror(errno) << std::endl;
return 1;
}
std::string a;
while(std::getline(jin, a)) {
std::cout << a << '\n';
}
return 0;
}
If you really do not want to use std::getline and std::string, you can, but it's much harder:
#include <cerrno>
#include <cstring>
#include <fstream>
#include <iostream>
int main() {
std::ifstream jin("Story.txt");
if(!jin) {
std::cerr << "File not opened: " << std::strerror(errno) << std::endl;
return 1;
}
char a[100];
while(true) {
jin.getline(a, 100);
std::cout << a; // output what we got
if(jin) {
// got a complete line, add a newline to the output
std::cout << '\n';
} else {
// did not get a newline
if(jin.eof()) break; // oh, the end of the file, break out
// reset the failbit to continue reading the long line
jin.clear();
}
}
}
jin.eof() will only return true if a eof-token is found, and this will not happend unless the file is open. That is what causing your infinite loop.
Then you would probably want something like this:
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
ifstream jin{"Story.txt"};
if (!jin)
{
cout << "File not opened" << endl;
return 1;
}
for (std::string a; std::getline(jin, a);) { // Read every line
cout << a << "\n";
}
// jin is closed when going out of scope so no need for close();
return 0;
}
I have written a small C++ program to set a property in a text file. The implementation is as following:
#include <cstdio>
#include <fstream>
#include <iostream>
#include <string>
using namespace std;
const string PROPFILE = "./propfile";
const string TEMPFILE = PROPFILE + ".tmp";
int setProp(const string &key, const string &val) {
try {
ifstream original(PROPFILE, ios::in);
ofstream tempfile(TEMPFILE, ios::out | ios::trunc);
for (string line; getline(original, line); ) {
if (line.compare(0, key.size(), key) == 0 && line[key.size()] == '=') {
tempfile << key << '=' << val << endl;
} else {
tempfile << line << endl;
}
}
cout << "original.rdstate()" << original.rdstate() << endl;
original.close();
tempfile.close();
} catch (ifstream::failure e) {
cerr << e.what() << endl;
}
if (rename(TEMPFILE.c_str(), PROPFILE.c_str()) != 0) {
cout << "Could not move " + TEMPFILE << "to " << PROPFILE << endl;
return 1;
}
return 0;
}
int main(int argc, const char *argv[]) {
try {
return setProp(argv[1], argv[2]);
} catch (logic_error) {
cout << "Invalid args" << endl;
return 1;
}
}
However, when I try to compile and execute it from commandline via ./a.out TESTPROP TESTVALUE, the value IS set as expected in propfile but rdstate() returns 6 (which means failbit and eofbit are set), I can't understand why are they getting set, can somebody explain ?
Contents of propfile before running ./a.out TESTPROP TESTVALUE are:
TESTPROP=NOTHING
After running the progam:
TESTPROP=TESTVALUE
I'm just a student, please don't mind if it's a dumb question :)
This is expected behaviour, the failbit is set whenever there is a failure to read the expected value. Even if that failure is because of end of file.
For instance see here
If no characters were extracted for whatever reason (not even the
discarded delimiter), getline sets failbit and returns.
Lets start with that I have absolutely no experience with C++ , but I got this project to connect a POS with a verifone. We do not have the standard verifone SDK but something custom.
At fist I needed to prepair data to send to C++ and C++ will send it to the Verifone. This is where I am getting stuck, I have a .txt file, which I can read with C++ but now I need to split the data.
This is my current code:
#include "stdafx.h"
#include <sstream>
#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
string file_get_contents(const char *filename)
{
ifstream in(filename);
if (in.fail())
{
cerr << "File not found: " << filename << endl;
return "";
}
std::stringstream buffer;
buffer << in.rdbuf();
in.close();
return buffer.str();
}
int main(int argc, char **argv)
{
vector<string> strings;
string contents = file_get_contents("C:/wamp/www/cmd/config.txt");
string s;
while (contents, s, '||') {
cout << s << endl;
strings.push_back(s);
}
cout << s; // ECHO CONTENTS
std::cin.ignore(); // pause
return 0;
}
With this code my console just stays blank, no data is being displayed.
The full string I am splitting is:
"notepad://amount=10320.53||session_id=7946548443287465/"
The result that I want is to get an array that uses "amount" and "session_id" as keys and their values as value.
What is the best way of achieving this?
I used the following code to actually display the string in my console which was working:
int main(int argc, char **argv)
{
string contents = file_get_contents("config.txt");
cout << contents; // ECHO CONTENTS
std::cin.ignore(); // pause
return 0;
}
This shows how to use a regex to extract the information you want, there are a lot of online resources on how to read files properly so I left that part out.
#include <iostream>
#include <regex>
#include <unordered_map>
#include <string>
int main(int argc, char **argv)
{
std::regex pattern("amount=([[:digit:]\\.]*)\\|\\|session_id=([[:digit:]]*)");
std::smatch results;
std::unordered_map<std::string, std::string> data;
std::string contents = "notepad://amount=10320.53||session_id=7946548443287465/";
//string contents = file_get_contents("C:/wamp/www/cmd/file.txt");
if(std::regex_search(contents, results, pattern))
{
data["amount"] = results[1];
data["session_id"] = results[2];
}
std::cout << "Amount: " << data["amount"] << std::endl;
std::cout << "Seesion ID: " << data["session_id"] << std::endl;
return 0;
}
I want to create a small code in C++ with the same functionality as "tail-f": watch for new lines in a text file and show them in the standard output.
The idea is to have a thread that monitors the file
Is there an easy way to do it without opening and closing the file each time?
Have a look at inotify on Linux or kqueue on Mac OS.
Inotify is Linux kernel subsystem that allows you to subscribe for events on files and it will report to your application when the even happened on your file.
Just keep reading the file. If the read fails, do nothing. There's no need to repeatedly open and close it. However, you will find it much more efficient to use operating system specific features to monitor the file, should your OS provide them.
Same as in https://stackoverflow.com/a/7514051/44729 except that the code below uses getline instead of getc and doesn't skip new lines
#include <iostream>
#include <string>
#include <fstream>
#include <sstream>
using namespace std;
static int last_position=0;
// read file untill new line
// save position
int find_new_text(ifstream &infile) {
infile.seekg(0,ios::end);
int filesize = infile.tellg();
// check if the new file started
if(filesize < last_position){
last_position=0;
}
// read file from last position untill new line is found
for(int n=last_position;n<filesize;n++) {
infile.seekg( last_position,ios::beg);
char test[256];
infile.getline(test, 256);
last_position = infile.tellg();
cout << "Char: " << test <<"Last position " << last_position<< endl;
// end of file
if(filesize == last_position){
return filesize;
}
}
return 0;
}
int main() {
for(;;) {
std::ifstream infile("filename");
int current_position = find_new_text(infile);
sleep(1);
}
}
I read this in one of Perl manuals, but it is easily translated into standard C, which, in turn, can be translated to istreams.
seek FILEHANDLE,POSITION,WHENCE
Sets FILEHANDLE's position, just like the "fseek" call of
"stdio".
<...>
A WHENCE of 1 ("SEEK_CUR") is useful for not moving the file
position:
seek(TEST,0,1);
This is also useful for applications emulating "tail -f". Once
you hit EOF on your read, and then sleep for a while, you might
have to stick in a seek() to reset things. The "seek" doesn't
change the current position, but it does clear the end-of-file
condition on the handle, so that the next "<FILE>" makes Perl
try again to read something. We hope.
As far as I remember, fseek is called iostream::seekg. So you should basically do the same: seek to the end of the file, then sleep and seek again with ios_base::cur flag to update end-of-file and read some more data.
Instead of sleeping, you may use inotify, as suggested in the other answer, to sleep (block while reading from an emulated file, actually) exactly until the file is updated/closed. But that's Linux-specific, and is not standard C++.
I needed to implement this too, I just wrote a quick hack in standard C++. The hack searches for the last 0x0A (linefeed character) in a file and outputs all data following that linefeed when the last linefeed value becomes a larger value. The code is here:
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int find_last_linefeed(ifstream &infile) {
infile.seekg(0,ios::end);
int filesize = infile.tellg();
for(int n=1;n<filesize;n++) {
infile.seekg(filesize-n-1,ios::beg);
char c;
infile.get(c);
if(c == 0x0A) return infile.tellg();
}
}
int main() {
int last_position=-1;
for(;;) {
ifstream infile("testfile");
int position = find_last_linefeed(infile);
if(position > last_position) {
infile.seekg(position,ios::beg);
string in;
infile >> in;
cout << in << endl;
}
last_position=position;
sleep(1);
}
}
#include <iostream>
#include <fstream>
#include <string>
#include <list>
#include <sys/stat.h>
#include <stdlib.h>
#define debug 0
class MyTail
{
private:
std::list<std::string> mLastNLine;
const int mNoOfLines;
std::ifstream mIn;
public:
explicit MyTail(int pNoOfLines):mNoOfLines(pNoOfLines) {}
const int getNoOfLines() {return mNoOfLines; }
void getLastNLines();
void printLastNLines();
void tailF(const char* filename);
};
void MyTail::getLastNLines()
{
if (debug) std::cout << "In: getLastNLines()" << std::endl;
mIn.seekg(-1,std::ios::end);
int pos=mIn.tellg();
int count = 1;
//Get file pointer to point to bottom up mNoOfLines.
for(int i=0;i<pos;i++)
{
if (mIn.get() == '\n')
if (count++ > mNoOfLines)
break;
mIn.seekg(-2,std::ios::cur);
}
//Start copying bottom mNoOfLines string into list to avoid I/O calls to print lines
std::string line;
while(getline(mIn,line)) {
int data_Size = mLastNLine.size();
if(data_Size >= mNoOfLines) {
mLastNLine.pop_front();
}
mLastNLine.push_back(line);
}
if (debug) std::cout << "Out: getLastNLines()" << std::endl;
}
void MyTail::printLastNLines()
{
for (std::list<std::string>::iterator i = mLastNLine.begin(); i != mLastNLine.end(); ++i)
std::cout << *i << std::endl;
}
void MyTail::tailF(const char* filename)
{
if (debug) std::cout << "In: TailF()" << std::endl;
int date = 0;
while (true) {
struct stat st;
stat (filename, &st);
int newdate = st.st_mtime;
if (newdate != date){
system("#cls||clear");
std::cout << "Print last " << getNoOfLines() << " Lines: \n";
mIn.open(filename);
date = newdate;
getLastNLines();
mIn.close();
printLastNLines();
}
}
if (debug) std::cout << "Out: TailF()" << std::endl;
}
int main(int argc, char **argv)
{
if(argc==1) {
std::cout << "No Extra Command Line Argument Passed Other Than Program Name\n";
return 0;
}
if(argc>=2) {
MyTail t1(10);
t1.tailF(argv[1]);
}
return 0;
}