How do I use parens '()' in a find command when building options from array? - bash

Question

I have a function that looks like this. I have stripped error handling, and the commands outside the function are to make sure I have something to look for in the example.
#!/bin/bash
findfiles() {
local path=$1
local mtime=$2
local prunedirs=$3
local -a fopts
fopts+=("$path")
[[ -n $prunedirs ]] && {
fopts+=('-type' 'd')
fopts+=('(' '-path')
fopts+=("${prunedirs// / -o -path }")
fopts+=(')' '-prune' '-o')
}
fopts+=('-type' 'f')
fopts+=('-writable')
fopts+=('-mtime' "+$mtime")
[[ -n $prunedirs ]] && fopts+=('-print')
echo "find ${fopts[*]}"
find "${fopts[#]}"
}
mkdir -p dir1/{dir2,dir3}
touch dir1/5daysago.txt -mt "$(date -d 'now - 5 days' +%Y%m%d%H%M)"
touch dir1/dir2/6daysago.txt -mt "$(date -d 'now - 6 days' +%Y%m%d%H%M)"
touch dir1/dir3/10daysago.txt -mt "$(date -d 'now - 10 days' +%Y%m%d%H%M)"
echo '---------------------------------------------'
findfiles dir1 4
echo '---------------------------------------------'
findfiles dir1 4 'dir1/dir2'
echo '---------------------------------------------'
findfiles dir1 4 "dir1/dir2 dir1/dir3"
This outputs the following:
---------------------------------------------
find dir1 -type f -writable -mtime +4
dir1/dir2/6daysago.txt
dir1/dir3/10daysago.txt
dir1/5daysago.txt
---------------------------------------------
find dir1 -type d ( -path dir1/dir2 ) -prune -o -type f -writable -mtime +4 -print
dir1/dir3/10daysago.txt
dir1/5daysago.txt
---------------------------------------------
find dir1 -type d ( -path dir1/dir2 -o -path dir1/dir3 ) -prune -o -type f -writable -mtime +4 -print
dir1/dir2/6daysago.txt
dir1/dir3/10daysago.txt
dir1/5daysago.txt
Notice that the third attempt does not prune the directories. If I copy and paste the find (escaping the parens) it works correctly.
$ find dir1 -type d \( -path dir1/dir2 -o -path dir1/dir3 \) -prune -o -type f -writable -mtime +4 -print
dir1/5daysago.txt
What am I doing wrong?

Answer 1

You need to add -o and the -path primary as separate array elements. Each directory to prune should be passed as a separate argument, not a single space-separated string.
findfiles() {
local path=$1
local mtime=$2
shift 2
n=$# # Remember for later
local -a fopts
fopts+=("$path")
if (( $# > 0 )); then
fopts+=(-type d '(')
while (( $# > 1 )); do
fopts+=(-path "$1" -o)
shift
done
fopts+=(-path $1 ')' -prune -o)
fi
fopts+=('-type' 'f')
fopts+=('-writable')
fopts+=('-mtime' "+$mtime")
# Now it's later
((n > 0)) && fopts+=('-print')
echo "find ${fopts[*]}"
find "${fopts[#]}"
}
findfiles dir1 4 "dir1/dir2" "dir1/dir3"

Answer 2

Change echo "find ${fopts[*]}" to declare -p fopts to unambiguously print the options. Doing so will show that the -o -path part is being added as a single word:
$ declare -p fopts
declare -a fopts=(
[0]="dir1" [1]="-type" [2]="d" [3]="(" [4]="-path"
[5]="dir1/dir2 -o -path dir1/dir3" [6]=")" [7]="-prune" [8]="-o" [9]="-type" [10]="f"
# ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[11]="-writable" [12]="-mtime" [13]="+4" [14]="-print"
)
To fix it you'll want to add each directory to prune to the array individually, something like:
local prunedirs=("${#:3}")
...
fopts+=(-type d '(' -false)
for dir in "${prunedirs[#]}"; do
fopts+=(-o -path "$dir")
done
fopts+=(')' -prune -o)
I've switched prunedirs to an array so it can handle directory names with whitespace.
It starts with an initial -false check so there's no need to check if prunedirs is empty. If it's empty the whole thing is still added but since it just says -type d '(' -false ')' -prune -o it's a no-op.
Also, notice you don't have to quote every single argument. It's fine to write -type d and such unquoted, the same as you would if you typed them at the command line. Only '(' and ')' need single quotes.