Szathmáry László honlapja @ DEIK | Nim2 / ANSI colors in the terminal

Let's see how to use ANSI colors in the terminal. I tried it under Linux only. Let's do it manually, without any library.

const
bold = "\e[1m"
blue = "\e[34m"
reset = "\e[0m"

echo bold & "Hello, Bold!" & reset # v1

echo bold & blue & "Hello, Bold and Blue!" & reset # v2

𝥶It prints the text in bold (v1). In v2, bold and blue are combined.

You can use a small helper function:

const
bold = "\e[1m"
reset = "\e[0m"

proc boldText(s: string): string =
bold & s & reset

echo boldText("Hello!") & " back to normal"

Demo

The "ac" prefix stands for "ANSI color".

const
# Reset
acReset = "\e[0m"

# Styles
acBold = "\e[1m"
acDim = "\e[2m"
acItalic = "\e[3m"
acUnderline = "\e[4m"
acBlink = "\e[5m"
acReverse = "\e[7m"
acHidden = "\e[8m"
acStrike = "\e[9m"

# Foreground colors
acBlack = "\e[30m"
acRed = "\e[31m"
acGreen = "\e[32m"
acYellow = "\e[33m"
acBlue = "\e[34m"
acMagenta = "\e[35m"
acCyan = "\e[36m"
acWhite = "\e[37m"

# Bright foreground colors
acBrightBlack = "\e[90m"
acBrightRed = "\e[91m"
acBrightGreen = "\e[92m"
acBrightYellow = "\e[93m"
acBrightBlue = "\e[94m"
acBrightMagenta = "\e[95m"
acBrightCyan = "\e[96m"
acBrightWhite = "\e[97m"

# Background colors
acBgBlack = "\e[40m"
acBgRed = "\e[41m"
acBgGreen = "\e[42m"
acBgYellow = "\e[43m"
acBgBlue = "\e[44m"
acBgMagenta = "\e[45m"
acBgCyan = "\e[46m"
acBgWhite = "\e[47m"

# Bright background colors
acBgBrightBlack = "\e[100m"
acBgBrightRed = "\e[101m"
acBgBrightGreen = "\e[102m"
acBgBrightYellow = "\e[103m"
acBgBrightBlue = "\e[104m"
acBgBrightMagenta = "\e[105m"
acBgBrightCyan = "\e[106m"
acBgBrightWhite = "\e[107m"

when isMainModule:
# Styles
echo acBold & "acBold" & acReset
echo acDim & "acDim" & acReset
echo acItalic & "acItalic" & acReset
echo acUnderline & "acUnderline" & acReset
echo acBlink & "acBlink" & acReset
echo acReverse & "acReverse" & acReset
echo acStrike & "acStrike" & acReset

# Foreground colors
echo acBlack & "acBlack" & acReset
echo acRed & "acRed" & acReset
echo acGreen & "acGreen" & acReset
echo acYellow & "acYellow" & acReset
echo acBlue & "acBlue" & acReset
echo acMagenta & "acMagenta" & acReset
echo acCyan & "acCyan" & acReset
echo acWhite & "acWhite" & acReset

# Bright foreground colors
echo acBrightBlack & "acBrightBlack" & acReset
echo acBrightRed & "acBrightRed" & acReset
echo acBrightGreen & "acBrightGreen" & acReset
echo acBrightYellow & "acBrightYellow" & acReset
echo acBrightBlue & "acBrightBlue" & acReset
echo acBrightMagenta & "acBrightMagenta" & acReset
echo acBrightCyan & "acBrightCyan" & acReset
echo acBrightWhite & "acBrightWhite" & acReset

# Background colors
echo acBgBlack & "acBgBlack" & acReset
echo acBgRed & "acBgRed" & acReset
echo acBgGreen & "acBgGreen" & acReset
echo acBgYellow & "acBgYellow" & acReset
echo acBgBlue & "acBgBlue" & acReset
echo acBgMagenta & "acBgMagenta" & acReset
echo acBgCyan & "acBgCyan" & acReset
echo acBgWhite & "acBgWhite" & acReset

# Bright background colors
echo acBgBrightBlack & "acBgBrightBlack" & acReset
echo acBgBrightRed & "acBgBrightRed" & acReset
echo acBgBrightGreen & "acBgBrightGreen" & acReset
echo acBgBrightYellow & "acBgBrightYellow" & acReset
echo acBgBrightBlue & "acBgBrightBlue" & acReset
echo acBgBrightMagenta & "acBgBrightMagenta" & acReset
echo acBgBrightCyan & "acBgBrightCyan" & acReset
echo acBgBrightWhite & "acBgBrightWhite" & acReset

# Combinations
echo acBold & acRed & "acBold & acRed" & acReset
echo acBold & acGreen & "acBold & acGreen" & acReset
echo acBold & acBrightYellow & "acBold & acBrightYellow" & acReset
echo acItalic & acCyan & "acItalic & acCyan" & acReset
echo acUnderline & acMagenta & "acUnderline & acMagenta" & acReset
echo acBold & acBgBlue & acWhite & "acBold & acBgBlue & acWhite" & acReset

Screenshot:

Same thing in C

In C, just use "\033" instead of "\e". The ASCII code of the ESC key is 27, which is 0o33 in octal, and 0x1b in hexa.

Everything else is the same:

#include <stdio.h>

#define BOLD "\033[1m"
#define BLUE "\033[34m"
#define RESET "\033[0m"

int main()
{
printf("%sHello, Bold!%s\n", BOLD, RESET);

printf("%s%sHello, Bold and Blue!%s\n", BOLD, BLUE, RESET);

return 0;
}

Same thing in Python

#!/usr/bin/env python3

RED = "\033[31m"
GREEN = "\033[32m"
BLUE = "\033[34m"
BOLD = "\033[1m"
RESET = "\033[0m"

def main():
print(f"{BOLD}Hello, Bold!{RESET}")
print(f"{BOLD}{BLUE}Hello, Bold and Blue!{RESET}")
print(f"{BOLD}{GREEN}Hello, Bold and Green!{RESET}")
print(f"{BOLD}{RED}Hello, Bold and Red!{RESET}")

##############################################################################

if __name__ == "__main__":
main()