Bash printf with empty columns

Question

Any idea how I can still include empty space in a row using printf ie when the column variable is empty? For example:

printf $GREEN"################################ SOURCED ###############################"$RESET
printf $GREEN'%-1s%-15s%-60s%-1s%s\n' '#'$RESET ' REGION NAME:' $OS_REGION_NAME $GREEN'#'$RESET
printf $GREEN"########################################################################"$RESET

Basically I am creating a box with that shows sourced variables. Sometimes some of the fields are empty. The box shouldn't collapse on the right when this happens. I thought I had this down correctly with my column settings on that middle line, but apparently it ignores the width if the column is empty.

The output should look something like this:

################################ SOURCED ###############################
# AUTH URL: blah blah blah                                             #
# REGION NAME: fcdnjcndkjcndkajcndkjcnklcnklsncklsnkcldnslc            #
########################################################################

but it ends up looking like this

################################ SOURCED ###############################
# AUTH URL: blah blah blah #
# REGION NAME: fcdnjcndkjcndkajcndkjcnklcnklsncklsnkcldnslc #
########################################################################

SOLUTION

The solution was to put the variables inside double quotes. Such a simple fix...

printf $GREEN'%-1s%-15s%-55s%-1s%s\n' '#'$RESET ' REGION NAME:' "$OS_REGION_NAME" $GREEN'#'$RESET

NOTE

The $GREEN and $RESET was for coloring set in another part of script.

Quote your variable expansions. If $OS_REGION_NAME is empty then the variable value is the empty string and the command becomes printf format '#reset' 'green#reset' i.e. you lose an argment. — Etan Reisner
– Etan Reisner, Commented Jul 8, 2015 at 13:40
Also there's no reason to use your $GREEN and $RESET variables in the format string on the first and third lines and no reason to use double quotes on those lines either (not that they hurt anything either). — Etan Reisner
– Etan Reisner, Commented Jul 8, 2015 at 13:42
The single quotes were example not literal (that's why I used green and reset and not $GREEN and $RESET. Use double quotes around any variable expansions. — Etan Reisner
– Etan Reisner, Commented Jul 8, 2015 at 13:43

Etan Reisner · Accepted Answer · 2015-07-08 13:46:22Z

1

The problem is that you failed to quote the expansion of $OS_REGION_NAME so when it is the empty string that entire argument to printf disappears (i.e. printf sees one fewer argument and everything after it slides up in the format string specifiers).

That being said I would also rewrite your lines this way

printf '################################ SOURCED ###############################\n' "$GREEN" "$RESET"
printf '$s%-1s%-15s%-60s%-1s%s\n' "$GREEN" "#$RESET" ' REGION NAME:' "$OS_REGION_NAME" "$GREEN#$RESET"
printf '%s########################################################################%s\n' "$GREEN" "$RESET"

answered Jul 8, 2015 at 13:46

Etan Reisner

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