Bash Prompt with Last Exit Code

Question

So, I\'ve been trying to customize by bash prompt so that it will look like

[feralin@localhost ~]$ _

with colors. I managed to get constant

Answer 1

To preserve original prompt format (not just colors), you could append following to the end of ~/.bashrc:

PS1_ORIG=$PS1 # original primary prompt value
PROMPT_COMMAND=__update_prompt # Func to be re-evaluated after each command is executed
__update_prompt() {
    local PREVIOUS_EXIT_CODE="$?"
    if [ $PREVIOUS_EXIT_CODE != 0 ]; then
        local RedCol='\[\e[0;31m\]'
        local ResetCol='\[\e[0m\]'
        local replacement="${RedCol}\u${ResetCol}"

        # Replace username color
        PS1=${PS1_ORIG//]\\u/]$replacement}
        ## Alternative: keep same colors, append exit code
        #PS1="$PS1_ORIG[${RedCol}error=$PREVIOUS_EXIT_CODE${ResetCol}]$ "
    else
        PS1=$PS1_ORIG
    fi
}

See also the comment about the alternative approach that preserves username color and just appends error code in red to the end of original prompt format

Answer 2

Improved @demure

I think this is important because there is not always exit status is 0 or 1.

if [ $EXIT != 0 ]; then
    PS1+="${Red}${EXIT}:\u${RCol}"      # Add red if exit code != 0
else
    PS1+="${Gre}${EXIT}:\u${RCol}"      # Also displays exit status
fi

Answer 3

If you don't want to use the prompt command there's two things you need to take into account:

1. getting the value of $? before anything else, otherwise it'll be overriden
2. escaping all the $'s in the PS1 (so it's not evaluated when you assign it)

Working example using a variable

PS1="\$(VALU="\$?" ; echo \$VALU ; date ; if [ \$VALU == 0 ]; then echo zero; else echo nonzero; fi) " 

Working example without a variable

Here the if needs to be the first thing, before any command that would override the $?.

PS1="\$(if [ \$? == 0 ]; then echo zero; else echo nonzero; fi) "

Notice how the \$() is escaped so it's not executed right away but each time PS1 is used. Also all the uses of \$?

Answer 4

Why i didn't think about that myself?) I found this very interesting and add this feature to my 'info-bar' project. Eyes will turn red if last command failed.

#!/bin/bash
eyes=(O o ∘ ◦ ⍤ ⍥) en=${#eyes[@]} mouth='_'                                                           
face () { # gen random face                                                                           
    [[ $error -gt 0 ]] && ecolor=$RED || ecolor=$YLW                                                  
    if [[ $1 ]]; then printf "${eyes[$[RANDOM%en]]}$mouth${eyes[$[RANDOM%en]]}"                       
                 else printf "$ecolor${eyes[$[RANDOM%en]]}$YLW$mouth$ecolor${eyes[$[RANDOM%en]]}$DEF"  
    fi                                                                                                
}                                                                                                     
info () { error=$?                                                                                    
    [[ -d .git ]] && {  # If in git project folder add git status to info bar output                  
        git_clr=('GIT' $(git -c color.ui=always status -sb)) # Colored output 4 info                  
        git_tst=('GIT' $(git                    status -sb)) # Simple  output 4 test                  
    }                                                                                                 
    printf -v line "%${COLUMNS}s"                            # Set border length                      
    date=$(printf "%(%a %d %b %T)T")                         # Date & time 4 test                     
    test=" O_o $PWD  ${git_tst[*]} $date o_O "               # Test string                            
    step=$[$COLUMNS-${#test}]; [[ $step -lt 0 ]] && step=0   # Count spaces                           
    line="$GRN${line// /-}$DEF\n"                            # Create lines                           
    home="$BLD$BLU$PWD$DEF"                                  # Home dir info                          
    date="$DIM$date$DEF"                                     # Colored date & time                    
           #------+-----+-------+--------+-------------+-----+-------+--------+                       
           # Line | O_o |homedir| Spaces | Git  status | Date|  o_O  |  Line  |                       
           #------+-----+-------+--------+-------------+-----+-------+--------+                       
    printf "$line $(face) $home %${step}s ${git_clr[*]} $date $(face) \n$line" # Final info string    
}                                                                                                     
PS1='${debian_chroot:+($debian_chroot)}\n$(info)\n$ '                                                 
case "$TERM" in xterm*|rxvt*)                                                                         
    PS1="\[\e]0;${debian_chroot:+($debian_chroot)} $(face 1) \w\a\]$PS1";;                            
esac 

Answer 5

As you are starting to border on a complex PS1, you might consider using PROMPT_COMMAND.
With this, you set it to a function, and it will be ran after each command to generate the prompt.

You could try the following in your ~/.bashrc

PROMPT_COMMAND=__prompt_command # Func to gen PS1 after CMDs

__prompt_command() {
    local EXIT="$?"             # This needs to be first
    PS1=""

    local RCol='\[\e[0m\]'

    local Red='\[\e[0;31m\]'
    local Gre='\[\e[0;32m\]'
    local BYel='\[\e[1;33m\]'
    local BBlu='\[\e[1;34m\]'
    local Pur='\[\e[0;35m\]'

    if [ $EXIT != 0 ]; then
        PS1+="${Red}\u${RCol}"      # Add red if exit code non 0
    else
        PS1+="${Gre}\u${RCol}"
    fi

    PS1+="${RCol}@${BBlu}\h ${Pur}\W${BYel}$ ${RCol}"
}

This should do what it sounds line you want. Take a look a my bashrc's sub file if you want to see all the things I do with my __prompt_command function.

Answer 6

I wanted to keep default Debian colors, print the exact code, and only print it on failure:

# Show exit status on failure.
PROMPT_COMMAND=__prompt_command

__prompt_command() {
    local curr_exit="$?"

    local BRed='\[\e[0;91m\]'
    local RCol='\[\e[0m\]'

    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '

    if [ "$curr_exit" != 0 ]; then
        PS1="[${BRed}$curr_exit${RCol}]$PS1"
    fi
}