When you write input in C++, you verify that the input is over by pressing enter, sadly that also changes the line.
But I still want to output something in that particular line.
How can I stay there? Is there a way to change how you confirm the end of the input?
I'm using the Cygwin64 Terminal
You can use getline.
#include <iostream>
int main() {
std::string str;
std::getline(std::cin, str, '.');
std::cout << str;
return 0;
}
Input
abcd.efgh
Output
abcd
Now '.' is an end of input.
getline Reference.
A simple getline() could be used. getline() takes in a delimiter character which can be utilized to "change how you confirm the end of the input". Without that parameter, the default delimiter is \n.
#include <iostream>
using namespace std;
int main()
{
string x;
getline(cin, x, 'm');
cout << x;
}
Input: test1test2mtest3
Output: test1test2
Special characters can also be used, like \t:
#include <iostream>
using namespace std;
int main()
{
string x;
getline(cin, x, '\t');
cout << x;
}
Input:
test1
test2
test3
Output:
test1
test2
A downside that it would still requires users to press Enter to complete the input, as shown above. Because, as #Öö Tiib pointed out:
C++ standard I/O streams are just that ... streams. The C++ is not
addressing from where these come and to where go.
In other words, generally C++ can't control the terminal input/output system, it only knows if something is inputted or if something should be outputted, and feed that to the terminal.
Info : https://en.cppreference.com/w/cpp/string/basic_string/getline
Related
I am learning C++. I want to take multiple line string as input but I can't. I am using getline() for it but it is taking only one line input. When I press enter for writing next line it stoped taking input and print the first line.
I want to give input like the example below
Hello, I am Satyajit Roy.
I want to make a program.
I love to travel.
But it takes only the first line input.
My code:
#include <iostream>
#include <string>
using namespace std;
int main()
{
string s;
getline(cin, s);
cout << s << endl;
return 0;
}
Please help me to know how can I do that.
Thank you.
Either you write a loop to read individual lines and concatenate them to a single string, thats what this answer suggests. If you are fine with designating a specific character to signal the end of the input, you can use the getline overload that takes a delimiter as parameter:
#include <iostream>
#include <string>
int main() {
std::string s;
std::getline(std::cin,s,'x');
std::cout << s;
}
The user would have to type an x to end input, so this input
Hello, I am Satyajit Roy.
I want to make a program.
I love to travel.
x
would result in this output:
Hello, I am Satyajit Roy.
I want to make a program.
I love to travel.
Of course this won't work when the string to be entered contains x, which renders the approach rather useless.
However, instead of using a "real" character as delimiter you can use the EOF character (EOF = end of file) like this:
std::getline(std::cin, s, static_cast<char>(EOF));
Then input is terminated by whatever your terminal interprets as EOF, eg Ctrl-d in linux.
Thanks to #darcamo for enlightening me on the EOF part.
You can only read one line at a time with std::getline if you don’t provide your own delimiter. If you want to accumulate multiple lines, one at a time, you need a place to put the result. Define a second string. Read a line at a time into s with std::getline, and then append s to the result string. Like this:
std::string result;
std::string s;
while (std::getline(std::cin, s))
result += s;
You can take several lines using the code below if you know how many lines you will input.
int line=3, t;
string s, bigString;
for(int i=0 ; i<line ; i++)
{
getline(cin,s); // This is to input the sentence
bigString += s + "\n";
}
cout << bigString;
If you don't know how many lines you will input (Input from file until end of file) then you can check this.
string s;
vector<string> all;
while(getline(cin,s))
{
all.push_back(s);// This is to input the sentence
}
for(auto i:all)
{
cout << i << endl;
}
I've been trying to read some information in from a .txt file in C++ but it's not all working like I expect. Here is some example code:
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
char words[255];
int value = 0;
ifstream input_stream("test.txt");
input_stream >> value;
input_stream.getline(words, 256);
cout << value << endl;
cout << words << endl;
}
And test.txt contains:
1234
WordOne WordTwo
What I expect is for the code to print the two lines contained in the text file, but instead I just get:
1234
I've been reading about getline and istream but can't seem to find any solutions so any help would be appreciated.
Thanks
The newline character remains in the input stream after the read of the integer:
// Always check result to ensure variables correctly assigned a value.
if (input_stream >> value)
{
}
Then, the call to getline() reads the newline character and stops, producing an empty string. To correct, consume the newline character before calling getline() (options include using getline() or ignore()).
Note there is a version std::getline() that accepts a std::string as its argument to avoid using a fixed sized array of char, which is used incorrectly in the posted code.
ifstream's getline method gathers input until one of two options is hit. Either a terminating character or the size passed in is reached. In your case, the newline terminator is encountered before the size is reached.
Use another getline to retrieve the second line of text.
Reference
The problem you are seeing is that the first newline after 1234 is not consumed by input_stream>>(int); so the next getline only reads to the end of that file.
This is a very constructed scenario, commonly found in schoolwork. The more common scenario when reading a textfile is to consider the entire file as linebased text.
In this case the more convenient
string line;
while( std::getline( input_stream, line ) ){
}
is appropriate, and way less error prone.
The textfile would commonly have a predefined format. Perhaps name = value lines, and are parsed as such after the line is read from the file.
Here is a somewhat corrected version of your original code:
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
char words[256]; // was 255
int value = 0;
ifstream input_stream("test.txt");
input_stream >> value;
input_stream.ignore(); // skip '\n'
input_stream.getline(words, 256);
cout << value << endl;
cout << words << endl;
}
Also, I would advise you to use a string instead of a char[] and use the other getline function.
I'm trying to store the input that user enters through console. so I need to include the "enter" and any white space.
But cin stops giving me input after the first space.
Is there a way to read whole lines until CTRL+Z is pressed, or something?
is there a way like readLines till CTRL+Z is pressed or something ??
Yes, precisely like this, using the free std::getline function (not the istream method of the same name!):
string line;
while (getline(cin, line)) {
// do something with the line
}
This will read lines (including whitespace, but without ending newline) from the input until either the end of input is reached or cin signals an error.
#include <iostream>
#include <string>
using namespace std;
int main()
string s;
while( getline( cin, s ) ) {
// do something with s
}
}
For my program, I wrote the following bit of code that reads every single character of input until ctrl+x is pressed. Here's the code:
char a;
string b;
while (a != 24)
{
cin.get(a);
b=b+a;
}
cout << b;
For Ctrl+z, enter this:
char a;
string b;
while (a != 26)
{
cin.get(a);
b=b+a;
}
cout << b;
I can't confirm that the ctr+z solution works, as I'm on a UNIX machine, and ctrl+z kills the program. It may or may not work for windows, however; You'd have to see for yourself.
#include <string>
#include <iostream>
int main()
{
std::cout << "enter your name: ";
std::string name;
std::getline(std::cin, name);
return 0;
}
You can use the getline function in c++
#include<iostream>
using namespace std;
int main()
{
char msg[100];
cin.getline(msg,100);
return 0;
}
I'm new to C++, and I'm trying to write a short C++ program that reads lines of
text from a file, with each line containing one integer key and one alphanumeric string value (no embedded whitespace). The number of lines is not known in advance, (i.e., keep reading lines until end of file is reached). The program needs to use the 'std::map' data structure to store integers and strings read from input (and to associate integers with strings). The program then needs to output string values (but not integer values) to standard output, 1 per line, sorted by integer key values (smallest to largest). So, for example, suppose I have a text file called "data.txt" which contains the following three lines:
10 dog
-50 horse
0 cat
-12 zebra
14 walrus
The output should then be:
horse
zebra
cat
dog
walrus
I've pasted below the progress I've made so far on my C++ program:
#include <fstream>
#include <iostream>
#include <map>
using namespace std;
using std::map;
int main ()
{
string name;
signed int value;
ifstream myfile ("data.txt");
while (! myfile.eof() )
{
getline(myfile,name,'\n');
myfile >> value >> name;
cout << name << endl;
}
return 0;
myfile.close();
}
Unfortunately, this produces the following incorrect output:
horse
cat
zebra
walrus
If anyone has any tips, hints, suggestions, etc. on changes and revisions
I need to make to the program to get it to work as needed, can you please
let me know?
Thanks!
See it:
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int main()
{
string name;
int value;
ifstream myfile("text.txt", ifstream::in);
while(myfile >> value >> name)
cout << name << endl;
return 0;
}
You are having problems because you attempt to read each line twice: first with getline and then with operator>>.
You haven't actually used std::map in any regard, at all. You need to insert the integer/string pair into the map, and then iterate over it as the output. And there's no need to close() the stream.
Instead of using "! myfile.eof()" use this code it will help.
ifstream is;
string srg;
is.open(filename);
while(getline(is,srg))
{//your code
}
Trying to get some basic understanding of console functionalities. I am having issues so consider the following...
#include "stdafx.h"
#include<iostream>
#include<conio.h>
using namespace std;
/*
This is a template Project
*/
void MultiplicationTable(int x);
int main()
{
int value = 0;
printf("Please enter any number \n\n");
getline(cin, value);
MultiplicationTable(value);
getchar();
return 0;
}
I actually based this off code from http://www.cplusplus.com/doc/tutorial/basic_io/ . My IDE is not recognizing getline() so of course when I compile the application. I get an error
'getline': identifier not found
Now take a look at this code
#include "stdafx.h"
#include<iostream>
#include<conio.h>
using namespace std;
/*
This is a template Project
*/
void MultiplicationTable(int x);
int main()
{
int value = 0;
printf("Please enter any number \n\n");
cin>>value;
MultiplicationTable(value);
getchar();
return 0;
}
When I execute this line of code the console window opens and immediately closes. I think I a missing something about cin. I do know that it delimits spaces but I don't know what else. what should I use for input to make my life easier.
The function getline() is declared in the string header. So, you have to add #include <string>.
It is defined as istream& getline ( istream& is, string& str );, but you call it with an int instead of a string object.
About your second question:
When I execute this line of code the console window opens and immediately closes
There is probably still a '\n' character from your input in the stream, when your program reaches the function getchar() (which I assume you put there so your window doesn't close). You have to flush your stream. An easy fix is, instead of getchar(), add the line
int c;
while((c = getchar()) != '\n'){}
This will flush your stream until the next line-break.
Remark: conio.h is not part of the c++ standard and obsolete.
The getline function reads strings, not integers:
#include <string>
#include <iostream>
using namespace std;
int main() {
string line;
getline( cin, line );
cout << "You entered: " << line << endl;
}
You are exiting the program before you can view the results because (I'm guessing) you double-clicked the .exe file from inside a Windows Explorer (or the Desktop) view in order to execute. Instead, go to Start, Run, type in cmd.exe and open a command window. Navigate to where your program resides. Type in your program's name on the command line and execute. It will stay open until you intentionally close the command window.