printf not displaying correctly in bash

Question

I have printf statements that are not displaying correctly in a Terminal window. The first two display correctly but the third printf "Writing to %s$output%s" "$biwhite" "$color_off" is not showing up except for the last few characters of $output

It feels like a bug of some sort. If I substitute echo for printf the line displays correctly, minus the coloring. I've tried putting all the statements in one printf with the same results. It is as though printf reallllly hates that one sentence. I'm at a loss as to what could be causing it. I'm working in OSX.

biwhite=$(tput bold)$(tput setaf 7)
#bired=$(tput bold)$(tput setaf 1)
color_off=$(tput sgr0)
date="$(date +%Y%m%d)"


while [[ $# -gt 0 ]] ; do

input="$1" #name $input as the first arugment sent to script

if [ -d "$input" ] ; then   #if argment is a directory, run md5deep
  target="${input%/}" #strip the trailing /, if any
  target="${target##*/}" #drop the leading directory componenets i.e. get basename
  output="$input"/"$target"_"$date"_checksums.md5 #set .md5 file to $output
  printf "%s${input##*/}%s is a directory.\n" "$biwhite" "$color_off"
  printf "Making checksums of all files in %s$input%s\n" "$biwhite" "$color_off"
  printf "Writing to %s$output%s" "$biwhite" "$color_off"
  md5deep -bre "$input" >> "$output" #create md5 hash (hashes) of $input and write results to $output
fi
shift

done

Charles Duffy · Accepted Answer · 2017-03-02 04:06:36Z

4

Generally speaking, the format string argument to printf should be constant. Thus:

printf '%s%s%s is a directory.\n' "$biwhite" "${input##*/}" "$color_off" # GOOD
printf 'Writing to %s%s%s\n' "$biwhite" "$output" "$color_off"           # GOOD

...or...

printf '%s is a directory.\n' "$biwhite${input##*/}$color_off"           # GOOD
printf 'Writing to %s\n' "$biwhite$output$color_off"                     # GOOD

As opposed to:

printf "%s${input##*/}%s is a directory.\n" "$biwhite" "$color_off"      # BAD
printf "Writing to %s$output%s\n" "$biwhite" "$color_off"                # BAD

Otherwise, behavior can be hard to predict:

Any % signs inside your "$output" can throw off how other positional arguments are interpreted.
Any backslash-escape sequences will be substituted with referenced characters -- a literal tab for \t, a carriage-return for \r, etc. (If you want this, use %b instead of %s in the specific positions where you want such substitutions to take place).

edited Mar 2, 2017 at 4:06

answered Mar 2, 2017 at 3:56

Charles Duffy

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2 Comments

Bleakley Over a year ago

Ahhh I see... $output is a file path that I want to be colorized when displayed so I thought I would need to bookend it with $biwhite and $color_off

Charles Duffy Over a year ago

Sure -- but by putting a %s placeholder for all three of "$biwhite", "$output" and "$color_off", or having only one placeholder and passing the full concatenated string for it, you can have that same effect without having the contents of output parsed as a format string itself.

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