How to get input as a string which contain spaces?

Question

I'm trying to make a program that will execute an entered command. I've tried:

const char* command = "echo Hello, World!";
system(command);

And this works fine. But I'd like to do so that the user has to type the command. And here's the problem. I've tried so:

const char* command;
cin >> command;
system(command.c_str());

And this also works fine, but only for a one-word command like cls. But if I try to enter a command like color a, the program saves my input data as two separate commands and executes color and next it tries to execute a and obviously the output is: 'a' is not recognized as an internal or external command, operable program or batch file.

So how to save the input data as a single string, which contains spaces?

A _single_ const char? That would be `const char in = std::cin.get();`... — Weak to Enuma Elish, Feb 21 '16 at 22:20

score 2 · Accepted Answer · answered Feb 21 '16 at 22:21

2

The problem you are encountering is that cin tokenizes the input on whitespace. If you want to obtain an entire line of input including non-line-ending whitespace, you should use std::getline().

answered Feb 21 '16 at 22:21

Code-Apprentice

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score 1 · Answer 2 · answered Feb 21 '16 at 22:21

1

I believe you're looking for std::getline() - this will process all input up until a specified delimiter, defaulting to \n:

std::string line;
if (std::getline(std::cin, line)) {
    ...
}

answered Feb 21 '16 at 22:21

Barry

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The if here isn't right. Getline returns the stream. – Rob L Feb 21 '16 at 22:25
@Rob Stream is convertible to `bool`. You don't do `if(stream >> x)`? – LogicStuff Feb 21 '16 at 22:25
That if statement implies that it is checking success or failure. The stream is always returned, even on failure. You shouldn't check it with an if (). – Rob L Feb 21 '16 at 22:27
1

@RobL It **is** checking success or failure. A stream is contextually convertible to `bool`. – Barry Feb 21 '16 at 22:28
@Rob Interesting... what check are you suggesting? – LogicStuff Feb 21 '16 at 22:29
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@RobL See [`operator bool()`](http://en.cppreference.com/w/cpp/io/basic_ios/operator_bool) – Barry Feb 21 '16 at 22:29
Check [cppreference](http://en.cppreference.com/w/cpp/string/basic_string/getline). The return value is the *input*. It doesn't matter what you pass it, it will return the input. You can't check that for failure. – Rob L Feb 21 '16 at 22:31
@Rob You just said you can't check `std::basic_istream` for failure, is that right? And what does `bool func()` do? You can't use it like `if(func())` because it always returns `bool`? – LogicStuff Feb 21 '16 at 22:34
1

@RobL That is wrong. You can absolutely check for failure. See [this example](http://coliru.stacked-crooked.com/a/0999d7549f91cdb2). Yes, the return value is the input stream - but the state of the input stream can change as a result of the operation, and it's that state that you're checking in the `if()` – Barry Feb 21 '16 at 22:34
Crud, never used that before. I always called fail... thanks. – Rob L Feb 21 '16 at 22:36
@RobL See also some of the answers to [this question](http://stackoverflow.com/q/5605125/2069064) – Barry Feb 21 '16 at 22:38

score 0 · Answer 3 · answered Feb 21 '16 at 22:22

0

std::getline(std::cin, command);

answered Feb 21 '16 at 22:22

Rob L

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How to get input as a string which contain spaces?

3 Answers3