When writing BASH or Perl scripts I find it dramatically improves its effectiveness and ease-of-use to employ colour and formatting controls. This is done through the use of ANSI Escape Codes.

The following is a partial listing of the VT100 control set. The ASCII “escape” character (decimal 027, hex 0x1B) is shown as \e since this is the code used in BASH and Perl. Bracketed tags are modifiable decimal parameters, e.g., {ROW} is replaced by a row number.

In Perl you just include “\e” in a variable or printed output, e.g.,:

print "\e[2J\ec";     #|Clear the screen, go Home, reset all settings

In BASH the technique is very similar:

Yellow=$"\e[01;33m"
Reset=$"\e[0m"

echo -n "This is ${Yellow}very${Reset} important!"

Some time in the 1960s or 1970s the Digital Equipment Corporation has a fabulously popular terminal called the VT100. This terminal had certain control sequences that would cause it to do things never done by display terminals until then. When a colour terminal was introduced the codes were expanded to include colour controls. These codes became a de facto standard that other terminals as well as the IBM PC (and subsequent clones) employed.

The VT100 codes have been expanded for PCs. I saw one site that called the codes “ANSIPlus”, but whether this is an official name or not I do not know. In any case, the codes below should work on all modern equipment.

To set a colour or other visual attribute (e.g., bold) use the code sequence \e[{attr1};…;{attrn}m. For example, if you want to set the font colour to bold yellow with a red background the code would be \e[1;33;41 or \e[41;33;01 (the sequence of the codes is not important, and you can zero-pad if you like).