I am using the ANSI escape code to print colored output.
I am getting proper colored output in vs code integrated terminal.
But when I am running the program in external command-prompt/Powershell, I am not getting the expected colored output.
My program looks something like this:
#define RESET "\033[0m"
#define RED "\x1B[31m"
#define GREEN "\x1B[32m"
int main(int argc, char** argv){
if(argc != 1){
std::cout << RED ">> Invalid Arguments!" RESET;
}else{
if(verify_password()){
...
...
...
}else{
std::cout << "\n>> " RED "Invalid Password!" RESET;
}
}
return 0;
}
Complete Code
NOTE: One weird thing I observed is that if I am entering the correct password then everything is working fine in both terminals(getting proper colors). But the problem is when either I am entering an incorrect password or an invalid amount of arguments
What might be the reason for this?
EDIT: I figured out a way to make it work. I find out that in order to make these escape codes work I need to have at least one call to system() function. But still, I am not sure how these things are connected.
Historically, consoles on Windows required use of the console API in the Windows SDK in order to do effects like color. But recent versions of Windows now support escape codes (and even UTF-8), but programs have to opt-in by calling SetConsoleMode with ENABLE_VIRTUAL_TERMINAL_PROCESSING. (Opting in preserves backward compatibility for older programs that aren't using escape codes or UTF-8.)
If you're getting color in some places and not others, then I'd guess there's a problem related to the state the terminal/console is in when sending the escape codes. For example, if the terminal thinks it's already processing an escape code and a new one begins, it might not recognize either. I suppose this might also be a problem if one part of the program uses escape codes but another part uses the Console API.
Related
This is my first question on stackoverflow. Pardon me if I haven't searched properly but I do not seem to find an explanation for this. Was just attempting an example from Bjourne Stroustroup's papers. Added my bits to see the array get re-sized as I type the text.
But it doesn't seem to work that way! getchar() simply waits till I am done with entering all the characters and then it will execute the loop. As per the logic, it doesn't actually go into the loop, get a character, perform its actions and then iterate. I am wondering if this is implementation specific, or intended to be like this?
I am on Ubuntu 14.04 LTS using Codeblocks with gcc 4.8.2. The source was in cpp files if that matters.
while(true)
{
int c = getchar();
if(c=='\n' || c==EOF)
{
text[i] = 0;
break;
}
text[i] = c;
if(i == maxsize-1)
{
maxsize = maxsize+maxsize;
text = (char*)realloc(text,maxsize);
if(text == 0) exit(1);
cout << "\n Increasing array size to " << maxsize << endl;
}
i++;
}
The output is as follows:
Array Size is now: 10
Please enter some text: this is some sample text. I would have liked to see the memory being realloced right here, but apparently that's not how it works!
Increasing array size to 20
Increasing array size to 40
Increasing array size to 80
Increasing array size to 160
You have entered: this is some sample text. I would have liked to see the memory being realloced right here, but apparently that's not how it works!
Array Size is now: 160
This has nothing to do with getchar directly. The "problem" is the underlying terminal, which will buffer your Input. The Input is sent to the program after you press enter. In Linux (dunno if there is a way in Windows) you can workaround this by calling
/bin/stty raw
in terminal or by calling
system ("/bin/stty raw");
in your program. This will cause getchar to immediately return the input character to you.
Dont forget to reset the tty behaviour by calling
/bin/stty cooked
when done!
Here is an example (for Linux):
#include <stdio.h>
#include <stdlib.h>
using namespace std;
int main() {
system ("/bin/stty raw");
char c = getchar();
system ("/bin/stty cooked");
return 0;
}
Also have a look at this SO Post: How to avoid press enter with any getchar()
Also, as suggested in the comments, have a look here: http://linux.die.net/man/3/termios especially on the command tcsetattr, which should work cross-platform.
Actually, tcsetattr does not apply to Windows (which is what is commonly referred to in this site as "cross-platform"). However, the question is tagged for Linux, so "cross-platform" is a moot point.
By default the standard input, output and error streams are set to
line-buffered (input)
block-buffered (output)
line-buffered (error)
You can change that using setbuf, but of course will not solve the problem (the answer calls for single-character input). POSIX terminal I/O (termios) lets you change via a system call any of the flags shown using stty. As a rule, you might call stty directly from a script, rarely from a C program.
Reading a single character is a frequently asked question, e.g.,
How can I read single characters from the terminal? (unix-faq)
How can I read a single character from the keyboard without waiting for the RETURN key? How can I stop characters from being echoed on the screen as they're typed? (comp.lang.c FAQ)
You could also use ncurses: the filter function is useful for programs that process a command-line (rather than a full-screen application). There is a sample program in ncurses-examples (filter.c) which does this.
So unfortunately from what I have read, there isn't a hex code for an up and down arrow. There is only a "friendly code."(See bottom of linked page) Does anyone know how to use this friendly code? Ideally, I just want a printf() or std::cout statement that prints the up or down arrow, in C/C++.
Thanks! http://www.yellowpipe.com/yis/tools/ASCII-HTML-Characters/
Answers that assume a Unicode environment will not work with the Windows console at all, because it does not use Unicode. It uses a code page to determine which characters can be displayed and what the character codes are; on my US-based Windows 7 system that is Code page 437. You can see that the arrows are at the top of the list, but unfortunately they're in the control character range. This means they are stripped out of normal output entirely. You need special console output functions to display them.
Edit: It appears you don't need special console output, only a few characters like '\x0a' are stripped. The following string should print all 4 arrows: "\x18\x19\x1a\x1b".
Disregard this answer if you're using the Windows API and not a console program.
You need to use a std::wstring:
#include <iostream>
#include <string>
int main()
{
std::wstring s(L"←→↑↓");
std::wcout << s << "\n";
}
Note that there is a difference between L"←→↑↓" and "←→↑↓". The latter is invalid, as neither ← nor → and certainly not ↑ and ↓ are valid ASCII characters.
On my machine, this gets printed as <-->??, probably because the terminal doesn't support the characters.
Simply copy and paste the text of the arrow keys from the code below and add it into your code.
#include<iostream>
using namespace std;
int main(){
// for up, down arrows.
cout<<" ↑ ↓ ";
return 0;
}
Well, the question may sound a bit too vague but here's 2 things I need to do and I'd definitely need some input on this :
Output something (e.g. using cout) with color (note: My TERM environment variable is set to xterm-color if that makes any difference; also, is there any uniform way to output colored text that's compatible with both pure mac and *nix terminals in general, so that the code is portable)
Output something at the same position on the terminal screen. OK, this may sound confusing too. Let's take a terminal app which simply outputs a progress percentage. It normally won't start a new line for that. The new value is shown at the very same spot. How is this doable? (Being a once Borland Pascal guy from the good old DOS days, the only thing I could think of is something to do with accessing video memory directly... or not?)
So... any ideas?
You probably want to use ncurses library. And ANSI escape codes can also be used for coloring.
1)
You can try Color cout , but that is not protable. I tried (ANSI escape codes) something like
cout << "\033[1;31mbold red text\033[0m\n";
cout << "\33[0;31m" << "Enter Your String here" << "\33[0m" << std::endl ;
You can also look at
How do I output coloured text to a Linux terminal?
2)
Are you looking for something like watch or top like app which are showing output at the same spot.
I have a C file running on Linux. It prints some lines in red (failures) and some in green (passes). As you might expect, it uses escape codes in the printf statements as follows:
#define BLACK "\033[22;30m"
#define GREEN "\033[22;31m"
printf(GREEN "this will show up green" BLACK "\n");
If the BLACK at the end wasn't there, the terminal text will continue to be green for everything. In case you didn't catch it, that's fine for a terminal window with a non-black background, but otherwise you'll end up with black-on-black. Not good! Running the program has this problem, as does capturing the output in a text file and then viewing the file with "more" or "less".
Is there a code to restore defaults instead of specifying a color at the end of the printf statement? This needs to be in C, but I would be interested in reading about other approaches.
I updated my macros as follows (note 31 is for red):
#define RESET_COLOR "\e[m"
#define MAKE_GREEN "\e[32m"
printf(MAKE_GREEN "this will show up green" RESET_COLOR "\n");
I found the following links helpful in understanding how these codes work:
http://www.phwinfo.com/forum/comp-unix-shell/450861-bash-shell-escapes-not-working-via-putty-ssh.html explains what these escape sequences do, and to use ncurses if portability is needed.
http://www.linuxselfhelp.com/howtos/Bash-Prompt/Bash-Prompt-HOWTO-6.html
ANSI codes shows even more escape sequences; It is useful to get the big picture
Try using:
#define RESETCOLOR "\033[0m"
That should reset it to the defaults.
More about these terminal codes can be found in ANSI escape code.
"\033[0m"
See ANSI escape code.
Type reset in the terminal.
There is a binary found in Linux and OS X called reset.
I'm writing a piece of code which deals with math variables and indices, and I'd need to print subscripts and superscripts on a CLI, is there a (possibly cross-platform) way to do that? I'm working in vanilla C++.
Note: I'd like this to be cross-platform, but since from the first answers this doesn't seem to be possible I'm working under MacOS and Ubuntu Linux (so bash).
Thank you
Since most CLIs are really only terminals (pretty dumb ones mostly but sometimes with color), the only cross-platform way I've ever done this is by allocating muliple physical lines per virtual line, such as:
2
f(x) = x + log x
2
It's not ideal but it's probably the best you're going to get without a GUI.
Following you extra information as to what platforms you're mainly interested in:
With Ubuntu at least, gnome-terminal runs in UTF-8 mode by default so the following code shows how to generate the superscripts and subscripts:
#include <stdio.h>
static char *super[] = {"\xe2\x81\xb0", "\xc2\xb9", "\xc2\xb2",
"\xc2\xb3", "\xe2\x81\xb4", "\xe2\x81\xb5", "\xe2\x81\xb6",
"\xe2\x81\xb7", "\xe2\x81\xb8", "\xe2\x81\xb9"};
static char *sub[] = {"\xe2\x82\x80", "\xe2\x82\x81", "\xe2\x82\x82",
"\xe2\x82\x83", "\xe2\x82\x84", "\xe2\x82\x85", "\xe2\x82\x86",
"\xe2\x82\x87", "\xe2\x82\x88", "\xe2\x82\x89"};
int main(void) {
int i;
printf ("f(x) = x%s + log%sx\n",super[2],sub[2]);
for (i = 0; i < 10; i++) {
printf ("x%s x%s ", super[i], sub[i]);
}
printf ("y%s%s%s z%s%s\n", super[9], super[9], super[9], sub[7], sub[5]);
return 0;
}
The super and sub char* arrays are the UTF-8 encodings for the Unicode code points for numeric superscripts and subscripts (see here). The given program will output my formula from above (on one line instead of three), then another test line for all the choices and a y-super-999 and z-sub-75 so you can see what they look like.
MacOS doesn't appear to use gnome-terminal as a terminal program but references here and here seem to indicate the standard terminal understands UTF-8 (or you could download and install gnome-terminal as a last resort).
I'd need to print subscripts and superscripts on a CLI, is there a cross-platform way to do that?
Only if you have a Unicode-capable terminal, which is far from guaranteed. Unicode defines a limited number of sub- and superscript ‘compatibility characters’, you certainly can't use it on any old letter:
₀₁₂₃₄₅₆₇₈₉₊₋₌₍₎ₐₑₒₓ
⁰¹²³⁴⁵⁶⁷⁸⁹⁺⁻⁼⁽⁾ⁿⁱ
Even then you're reliant on there being a glyph for it in the console font, which is also far from guaranteed. Superscript 2 and 3 are likely to exist as they're present in ISO-8859-1; the others may well not work.