Question

I have a small script that colorizes compiler(maven) output so errors won’t be overlooked anymore.

#!/bin/sh
export TEXT_YELLOW=`tput setaf 3`
export TEXT_RED=`tput setaf 1`
export RESET_FORMATTING=`tput sgr0`

mvn $* | sed \
-e "s/\(\[WARNING\].*\)/${TEXT_YELLOW}\1${RESET_FORMATTING}/g" \
-e "s/\(\[ERROR\].*\)/${TEXT_RED}\1${RESET_FORMATTING}/g"

Problem is the shell within a shell feature my compiler has (mvn cli:execute-phase). There a command prompt like maven2> should be visible on screen and the user is then able to type in commands. Unfortunately due to my script I see nothing but a blinking cursor. Only when I press the enter key the maven2> prompt-prefix-text pops up.

My guess is that sed is waiting for an EOL before it prints something on screen. To fix it I would have to look if the stream starts with the string maven2>. If it does then print out directly to terminal, otherwise forward it to sed. Is it possible in bash?

Answer 1

Okay, I found a solution. I tried a lot of things but was unable to solve the problem purely with bash in the end. So I wrote a python script instead and it works. Just pipe the maven output to the script like mvn cli:execute-phase | colorize.py. It is also possible to write an alias in your bashrc so all maven calls have colorized output.

#!/usr/bin/python
# Same as regular mvn command but with colored output.

import sys, subprocess, os, time

def colorize( line ):
    red = '\033[1;31m'
    yellow = '\033[1;33m'
    endcolor = '\033[1;m'

    if ("[ERROR]" in line) or ("ERROR" in line ) or ( "Failures" in line ) or ( "Errors" in line ):        
        print red + line + endcolor,    
    elif ("[WARNING]" in line) or ( "WARN" in line ):
        print yellow + line + endcolor,
    else:
        print line,


line=""
printPrompt = True
while True:

    c = sys.stdin.read(1)

    if not c:
        # eof
        break

    line = line + c

    if printPrompt:
        if line.startswith("maven2>"):        
            print "maven2>",
            sys.stdout.flush()
            printPrompt = False
    else:
        # rewrite the current line to console
        sys.stdout.write('\r')
        print line,
        sys.stdout.flush()

    if c.endswith("\n"):
        colorize(line)
        line = ""
        printPrompt = True