I have a bash script that uses printf to printout some colored STDOUT. I noticed that sometimes it insert spaces:

#!/usr/bin/env bash

### define colors
BLACK=$(tput setaf 0)
RED=$(tput setaf 1)
GREEN=$(tput setaf 2)
YELLOW=$(tput setaf 3)
LIME_YELLOW=$(tput setaf 190)
POWDER_BLUE=$(tput setaf 153)
BLUE=$(tput setaf 4)
MAGENTA=$(tput setaf 5)
CYAN=$(tput setaf 6)
WHITE=$(tput setaf 7)
BRIGHT=$(tput bold)
NORMAL=$(tput sgr0)
BLINK=$(tput blink)
REVERSE=$(tput smso)
UNDERLINE=$(tput smul)

### 0. CHECK
# 1. docker
echo
printf "@s\n" " 0.1. checking ${BRIGHT}${GREEN}docker${NORMAL} ..."
if [ ! "$(command -v docker)" ]; then
  printf "@s\n" "   -> Please install ${BRIGHT}${GREEN}docker${NORMAL} first: ${BLUE}${UNDERLINE}https://github.com/cccnrc/diagnosticator-mac#dependencies${NORMAL}"
  exit 1
else
  printf "@s\n" "   -> ${BRIGHT}${GREEN}docker${NORMAL} found"
fi
# 2. docker-compose
printf "@s\n" " 0.2. checking ${BRIGHT}${GREEN}docker-compose${NORMAL} ..."
if [ ! "$(command -v docker-compose)" ]; then
  printf "@s\n" "   -> Please install ${BRIGHT}${GREEN}docker-compose${NORMAL} first: ${BLUE}${UNDERLINE}https://github.com/cccnrc/diagnosticator-mac#dependencies${NORMAL}"
  exit 1
else
  printf "@s\n" "   -> ${BRIGHT}${GREEN}docker-compose${NORMAL} found"
fi
echo

I got this output:

Why are there much more spaces before -> docker found than -> docker-compose found line when the printf command spaces are exactly the same?

CodePudding user response：

Color codes also take bytes, but are invisible. You have to take them into account.

printf "%*s\n" \
    $((40   ${#BRIGHT}   ${#GREEN}   ${#NORMAL})) \
    "   -> ${BRIGHT}${GREEN}docker${NORMAL} found"

In Bash instead of:

if [ ! "$(command -v docker)" ]

(prefer [[ over [ anyway, but) prefer:

if hash docker 2>/dev/null

hash will hash the command location, which will make any subsequent invocation faster, because Bash will not have to find the command again. And both $( and [ spawn a subprocess, which is way slower than calling builtin hash.