Make web-safe colors using Bash

When computer monitors have a limited color palette, web designers often use a set of web-safe colors to create websites. Although modern websites displayed on newer devices can display more colors than the original web-safe palette, I sometimes like to refer to web-safe colors when creating web pages. This way I know my page will look good everywhere.

You can find web safe palettes online, but I wanted to have my own copy for easy reference. You can also create one using a for loop in Bash.

Bash for loop

The syntax of the for loop in Bash is as follows:

for 变量 in 集合 ; do 语句 ; done

For example, suppose you want to print all numbers from 1 to 3. You can quickly write a for loop on the Bash command line to do the job for you:

$ for n in 1 2 3 ; do echo $n ; done123

The semicolon is the standard Bash statement delimiter. They allow you to write multiple commands in one line. If you were to include this for loop in a Bash script file, you could replace the semicolons with newlines and write the for loop like this:

for n in 1 2 3doecho $ndone

I like it Putting do and for on the same line makes it easier for me to read:

for n in 1 2 3 ; doecho $ndone

Multiple for loops at once

You can put a loop Put in another loop. This helps you iterate over multiple variables and do more than one thing at a time. Suppose you want to print out all combinations of the letters A, B, and C with the numbers 1, 2, and 3. You can do this in Bash using two for loops, like this:

#!/bin/bashfor number in 1 2 3 ; dofor letter in A B C ; doecho $letter$numberdonedone

If you put these lines in a Bash script called for.bash file and run it, you'll see nine lines showing all combinations of letters paired with each number:

$ bash for.bashA1B1C1A2B2C2A3B3C3

Traverse Web Safe Colors

Web safe colors are derived from hex Colors #000 (black, where red, green, and blue are all zero) to #fff (white, where red, green, and blue are all highest), each The steps for hexadecimal values ​​are 0, 3, 6, 9, c, and f.

You can generate a list of all combinations of web-safe colors using three for loops in Bash, which loop over the red, green, and blue values.

#!/bin/bashfor r in 0 3 6 9 c f ; dofor g in 0 3 6 9 c f ; dofor b in 0 3 6 9 c f ; doecho "#$r$g$b"donedonedone

If you save this in a new Bash script called websafe.bash and run it, you'll see an iteration of the hex values ​​for all the web-safe colors:

$ bash websafe.bash | head#000#003#006#009#00c#00f#030#033#036#039

要制作可用作 Web 安全颜色参考的 HTML 页面，你需要使每个条目成为一个单独的 HTML 元素。将每种颜色放在一个 

#!/bin/bashfor r in 0 3 6 9 c f ; dofor g in 0 3 6 9 c f ; dofor b in 0 3 6 9 c f ; doecho "
#$r$g$b
"donedonedone

$ bash websafe.bash > websafe.html

#!/bin/bashcat<
EOFfor r in 0 3 6 9 c f ; dofor g in 0 3 6 9 c f ; dofor b in 0 3 6 9 c f ; doecho "
#$r$g$b
"donedonedonecat<EOF

$ bash websafe.bash > websafe.html