I'm new to bash and sed. I'd like to take the output of who and indent each line, coloring the username in the process. Here's what I have so far:
#!/bin/bash
BOLD="\e[1m"
UNBOLD="\e[0m"
GREEN="\e[32m"
DEFAULT="\e[39m"
who | sed "s@\\([a-z_][a-z0-9_]{0,30}\\) \\(.*\\)@\\t$BOLD$GREEN\\1$DEFAULT$UNBOLD\\2@"
Right now it just prints the output without any changes. I'm pretty sure the problem has to do with escaping, but I'm not sure what needs it and what doesn't.
Thanks!
You have two problems. The first one is that your sed command is not doing what you're expecting. Let's fix that first. I guess you want to write the user in bold green, and the rest in default unbold. This should be better:
#!/bin/bash
bold="\e[1m"
unbold="\e[0m"
green="\e[32m"
default="\e[39m"
who | sed "s/^\([[:alpha:]_]\+\)\(.*\)/$bold$green\1$default$unbold\2/"
Or is it really better? you see the ugly codes instead of the nice colors. And this is your second problem. This is how we'll fix it:
#!/bin/bash
bold=$'\e[1m'
unbold=$'\e[0m'
green=$'\e[32m'
default=$'\e[39m'
who | sed "s/^\([[:alpha:]_]\+\)\(.*\)/$bold$green\1$default$unbold\2/"
or, if you don't like ANSI-C quotings:
#!/bin/bash
bold=$(echo -e "\e[1m")
unbold=$(echo -e "\e[0m")
green=$(echo -e "\e[32m")
default=$(echo -e "\e[39m")
who | sed "s/^\([[:alpha:]_]\+\)\(.*\)/$bold$green\1$default$unbold\2/"
Note. It is considered very bad practice to use uppercase variable names in bash. I know you'll see a lot of people doing it, but it's really wrong. That's why I lowercased all your variables.
PATH and hence screwed up everything. They would have saved hours if they only had respected this: use lowercase variable names in bash.