I'm new to C and I came across this code and it was confusing me:
sprintf(banner1, "\e[37╔═╗\e[37┌─┐\e[37┌┐┌\e[37┌─┐\e[37┌─┐\e[37┌─┐\e[37┌─┐\e[37m\r\n");
sprintf(banner2, "\e[37╠═╝\e[37├─┤\e[37│││\e[37│ ┬\e[37├─┤\e[37├┤\e[37 ├─┤\e[37m\r\n");
sprintf(banner3, "\e[37╩ \e[37┴ ┴┘\e[37└┘\e[37└─┘\e[37┴ ┴\e[37└─┘\e[37┴ ┴\e[37m\r\n");
I was just confused as I don't know what do \e[37 and \r\n mean. And can I change the colors?
This looks like an attempt to use ANSI terminal color escapes and Unicode box drawing characters to write the word "PANGAEA" in a large, stylized, colorful manner. I'm guessing it's part of a retro-style BBS or MUD system, intended to be interacted with over telnet or ssh. It doesn't work, because whoever wrote it made a bunch of mistakes. Here's a corrected, self-contained program:
#include <stdio.h>
int main(void)
{
printf("\e[31m╔═╗\e[32m┌─┐ \e[33m┌┐┌\e[34m┌─┐\e[35m┌─┐\e[36m┌─┐\e[37m┌─┐\e[0m\n");
printf("\e[31m╠═╝\e[32m├─┤ \e[33m│││\e[34m│ ┬\e[35m├─┤\e[36m├┤ \e[37m├─┤\e[0m\n");
printf("\e[31m╩ \e[32m┴ ┴┘\e[33m┘└┘\e[34m└─┘\e[35m┴ ┴\e[36m└─┘\e[37m┴ ┴\e[0m\n");
return 0;
}
The mistakes were: using \r\n instead of plain \n, leaving out the m at the end of each and every escape sequence, and a number of typos in the actual letters (missing spaces and the like).
I deliberately changed sprintf(bannerN, ... to printf to make it a self-contained program instead of a fragment of a larger system, and changed the actual color codes used for each letter to make it a more interesting demo. When I run this program on my computer I get this output:
The program will only work on your computer if your terminal emulator supports both ANSI color escapes and printing UTF-8 with no special ceremony. Most Unix-style operating systems nowadays support both by default; I don't know about Windows.
Related
Is it possible to highlight text with your cursor in any program, like you do with str+c and start a tool with the highlighted text as argument?
As far as I know, in Linux as well as in Windows, one can call a script/program with a custom shortcut. I assume str+c just does the same, calling a little program with the highlighted text as argument. How to replicate this?
For demonstration purposes, let's take this C - program printing the value it was called with:
#include <stdio.h>
int main(int argc, char**argv){
if(argc == 2){
printf("program called with: '%s'\n", argv[1]);
}
}
Can one type the text "HelloWorld" in Word for example, highlight it, and press something like str+alt+p, calling
someprogram.exe HelloWorld
or as for Linux
someprogram HelloWorld
I am really curious if this is possible.
Edit: I'm interested to know, how to replicate the clipboard.exe functionality. I have written a program "write_custom.exe" storing anything given as argument (argv[1]) in a text-file, after deleting it's previous content. Other programs can read the content of this text-file and so are able to use this custom clipboard. It's purpose is mainly for self-teaching.
As I am at the beginning of my codeing career, I only know C, but I am open for solutions in other languages as well. My goal is to run this write_custom.exe, with highlighted text as argument, on my computer and my Linux-VM.
You might want to check out ncurses (Linux) and Console API (Windows). The code will not be cross-platform, but you can pretty easily write some code to make them share some basic behavior :).
I am doing a basic C tutorial. In an example this code was given to introduce escape sequences:
#include <stdio.h>
int main()
{
printf("This is a \"sample text\"\n");
printf("\tMore text\n");
printf("This is getting overwritten\r");
printf("By this, another sample text\n");
printf("The spa \bce is removed.\n");
return 0;
}
The console output is expected to look like this:
This is a "sample text"
More text
By this, another sample text
The space is removed.
Instead, I get this:
This is a "sample text"
More text
This is getting overwritten
By this, another sample text
The spa ce is removed.
I am using Eclipse Cpp Oxygen on Windows and the Cygwin toolchain to compile und run the code. I don't know what I'm doing wrong and I thought I'd ask here for help.
The console built in to Eclipse does not support the \r, \b (and \f) characters.
There is a long standing bug 76936 for this which has been open for 14 years. But doesn't look like being fixed.
In linux you example works exactly as you expect. Probably in windows the \r is considered like \n.
Instead on linux terminal the \r put (correctly) the cursor on the first char of the row.
I'm programming in windows, but in my C console some characters (like é, à, ã) are not recognizable. I would like to see how can I make widows interpret those chars as using unicode in the console or utf-8.
I would be glad for some enlightening.
Thank you very much
By console do you mean cmd.exe? It doesn't handle Unicode well, but you can get it to display "ANSI" characters by changing the display font to Lucida Console and changing the code page from "OEM" to "ANSI." By the choice of characters you seem to be Western European, so try giving this command before running your application:
chcp 1252
If you want to try your luck with UTF-8 output use chcp 65001 instead.
Although I completely agree with Joni's answer, I think it can be added a detail:
Since Telmo Vaz asked about how to solve this problem for C programs, we can consider the alternative of adding a system command inside the code:
#include <stdlib.h> // To use the function system();
#include <stdio.h>
int main(void) {
system("CHCP 1252");
printf("Now accents are right: áéíüñÇ \n");
return 0;
}
EDIT It is a good idea to do some experiments with codepages. Check the following table for information (under Windows):
Windows Codepages
Silly question but,
Is it possible to break a line on stdout without the line feed using printf();? If not, any tips on how I would overwrite 2+ lines, if possible?
I'm trying to generate sort of a progress bar but on multiple lines.
Any ideas?
EDIT:
So yeah I accepted the below answer although it won't work for my specific case.
I'm trying to overwrite 2+lines
rather than a single line.
printf("12345\r");
fflush(stdout);
printf("67890\n");
The result of which is $ ./a.out 67890
But what I'm trying to achieve is have 2+ lines be overwritten with new data.
Similar to a progress bar but on 2+ lines except I have a percentage number for some data.
To rewrite all (or part) of a line, you need to use the correct number of backspace characters. Eg:
printf("some text");
printf("\b\b\b\bstuff");
Will output:
some stuff
This is fine for simple stuff; for something more complex you should use ncurses which uses ANSI-escape cleverness to manipulate the cursor around the screen.
If your terminal (or, much more likely, terminal emulator) supports VT100-style escape sequences, you can print specific code sequences to control the cursor position, clear some or all of the screen/window, etc.
For example, to move the cursor up 1 line:
printf("\x1b[A");
fflush(stdout);
To move the cursor up 2 lines, either do that twice or:
printf("\x1b[2A"});
fflush(stdout);
These are commonly referred to as ANSI escape codes; the link is to a Wikipedia article that lists many of them. They were first implemented by the old DEC VT-100 terminal, which is emulated by most modern terminals and emulators.
And this:
printf("\x1b[J");
fflush(stdout);
will clear part of the screen, from the current cursor position to the bottom.
These sequences should be enough to do what you need. (They might not work in a Windows command window.)
More portably, if your system supports it, you can use termcap or terminfo to determine the proper command sequences for your current terminal (as determined by the $TERM environment variable). The tput command lets you do this on the command line; man tput for more information. In practice, you're unlikely to find a system these days that supports termcap or terminfo with a terminal that's not VT100-compatible; printing raw escape sequences is strictly not portable, but probably good enough.
A suggestion: your program should probably have an option to inhibit any such control sequences; for example, if a user who wants to redirect the output to a file won't want to have those escape sequences in the file. Some programs use control sequences only if they can determine that stdout is a terminal, but an explicit option is also a good idea.
*UPDATE: *
Here's a program I threw together that demonstrates how to do this with the terminfo. It should work on just about any Unix-like system.
#include <stdio.h>
#include <stdlib.h>
#include <curses.h>
#include <term.h>
#include <unistd.h>
int main(void) {
const char *term = getenv("TERM");
if (term == NULL) {
fprintf(stderr, "TERM environment variable is not set\n");
exit(EXIT_FAILURE);
}
setterm(term);
for (int i = 0; i < 10; i ++) {
putp(tparm(clr_eos));
printf("%d\n%d\n", i, i+1);
sleep(1);
putp(tparm(parm_up_cursor, 2));
}
return 0;
}
Is this possible?
I know it's possible in the command prompt using COLOR ##
but is it possible in C using bloodshed?
Thanks,
What operating system? What terminal do you have available? Note that this has nothing to do with C, let alone bloodshed. You output a string which the terminal may or may not choose to interpret as a color. You have to see how to do that with your terminal. The solution of course is not portable. One such example for a terminal supporting escape sequences is
printf("\\x1b[1;33mThis is yellow\\x1b[m(Back to default)\n");
You may be interested in ANSI terminal's color escape sequences
You may also want to look for libraries that do that for limited number of terminals. For example, ncurses could help you in Linux.
If you're on *nix, osx, or using cygwin msys on windows, your terminal should support the ANSI sequences Fred Larson mentions (not sure about osx). The normal windows terminal does not. But bloodshed can use cygwin, so you're in luck.
Here's an example:
#include <stdio.h>
#define BOLDMAGENTA "\033[1;35m"
#define BOLDGREEN "\033[1;32m"
int main(void) {
printf("%shello %sworld\n", BOLDMAGENTA, BOLDGREEN);
return 0;
}
Note that this leaves the terminal in bright green, but if your prompt sets colours, that will get reset.
Here's some explanation of ANSI escape codes:
http://en.wikipedia.org/wiki/ANSI_escape_code