bash_profile

 From Andrzej Szelachowski's ~/.bash_profile:


#  Note that a variable may require special treatment
#+ if it will be exported.

DARKGRAY='\e[1;30m'
LIGHTRED='\e[1;31m'
GREEN='\e[32m'
YELLOW='\e[1;33m'
LIGHTBLUE='\e[1;34m'
NC='\e[m'

PCT="\`if [[ \$EUID -eq 0 ]]; then T='$LIGHTRED' ; else T='$LIGHTBLUE'; fi; 
echo \$T \`"

#  For "literal" command substitution to be assigned to a variable,
#+ use escapes and double quotes:
#+       PCT="\` ... \`" . . .
#  Otherwise, the value of PCT variable is assigned only once,
#+ when the variable is exported/read from .bash_profile,
#+ and it will not change afterwards even if the user ID changes.


PS1="\n$GREEN[\w] \n$DARKGRAY($PCT\t$DARKGRAY)-($PCT\u$DARKGRAY)-($PCT\!
$DARKGRAY)$YELLOW-> $NC"

#  Escape a variables whose value changes:
#        if [[ \$EUID -eq 0 ]],
#  Otherwise the value of the EUID variable will be assigned only once,
#+ as above.

#  When a variable is assigned, it should be called escaped:
#+       echo \$T,
#  Otherwise the value of the T variable is taken from the moment the PCT 
#+ variable is exported/read from .bash_profile.
#  So, in this example it would be null.

#  When a variable's value contains a semicolon it should be strong quoted:
#        T='$LIGHTRED',
#  Otherwise, the semicolon will be interpreted as a command separator.


#  Variables PCT and PS1 can be merged into a new PS1 variable:

PS1="\`if [[ \$EUID -eq 0 ]]; then PCT='$LIGHTRED';
else PCT='$LIGHTBLUE'; fi; 
echo '\n$GREEN[\w] \n$DARKGRAY('\$PCT'\t$DARKGRAY)-\
('\$PCT'\u$DARKGRAY)-('\$PCT'\!$DARKGRAY)$YELLOW-> $NC'\`"

# The trick is to use strong quoting for parts of old PS1 variable.