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Using find . -print0 seems to be the only safe way of obtaining a list of files in bash due to the possibility of filenames containing spaces, newlines, quotation marks etc.

However, I'm having a hard time actually making find's output useful within bash or with other command line utilities. The only way I have managed to make use of the output is by piping it to perl, and changing perl's IFS to null:

find . -print0 | perl -e '$/="\0"; @files=<>; print $#files;'

This example prints the number of files found, avoiding the danger of newlines in filenames corrupting the count, as would occur with:

find . | wc -l

As most command line programs do not support null-delimited input, I figure the best thing would be to capture the output of find . -print0 in a bash array, like I have done in the perl snippet above, and then continue with the task, whatever it may be.

How can I do this?

This doesn't work:

find . -print0 | ( IFS=$'\0' ; array=( $( cat ) ) ; echo ${#array[@]} )

A much more general question might be: How can I do useful things with lists of files in bash?

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What do you mean by doing useful things? –  Balázs Pozsár Jul 12 '09 at 22:04
Oh, you know, the usual things arrays are useful for: finding out their size; iterating over their contents; printing them out backwards; sorting them. That kind of thing. There are a wealth of utilities in unix for doing these things with data: wc, bash's for-loops, tac and sort respectively; but these all seem useless when dealing with lists which might have spaces or newlines in them. I.e. filenames. Piping data around with null valued input-field-separators seems to be the solution, but very few utilities can handle this. –  Idris Jul 12 '09 at 23:14
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11 Answers

up vote 44 down vote accepted

Shamelessly stolen from Greg's BashFAQ:

unset a i

Note that the redirection construct used here (cmd1 < <(cmd2)) is similar to, but not quite the same as the more usual pipeline (cmd2 | cmd1) -- if the commands are shell builtins (e.g. while), the pipeline version executes them in subshells, and any variables they set (e.g. the array a) are lost when they exit. cmd1 < <(cmd2) only runs cmd2 in a subshell, so the array lives past its construction. Warning: this form of redirection is only available in bash, not even bash in sh-emulation mode; you must start your script with #!/bin/bash.

Also, because the file processing step (in this case, just a[i++]="$file", but you might want to do something fancier directly in the loop) has its input redirected, it cannot use any commands that might read from stdin. To avoid this limitation, I tend to use:

unset a i
done 3< <(find /tmp -type f -print0)

...which passes the file list via unit 3, rather than stdin.

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Ahhh almost there... this is the best answer yet. However, I've just tried it on a directory containing a file with a newline in its name, and upon inspecting that element using echo ${a[1]}, the newline seems to have become a space (0x20). Any idea why this is happening? –  Idris Jul 14 '09 at 0:40
What version of bash are you running? I've had trouble with older versions (unfortunately I don't remember precisely which) not dealing with newlines and deletes (\177) in strings. IIRC, even x="$y" wouldn't always work right with these characters. I just tested with bash 2.05b.0 and 3.2.17 (the oldest and newest I have handy); both handled newlines properly, but v2.05b.0 ate the delete character. –  Gordon Davisson Jul 14 '09 at 7:34
I've tried it on 3.2.17 on osx, 3.2.39 on linux and 3.2.48 on netBSD; all turn newline into space. –  Idris Jul 14 '09 at 13:09
-d '' is equivalent to -d $'\0'. –  l0b0 Oct 31 '11 at 13:38
An easier way to add an element to the end of an array is: arr+=("$file") –  dogbane Oct 2 '12 at 10:06
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Maybe you are looking for xargs:

find . -print0 | xargs -r0 do_something_useful

The option -L 1 could be useful for you too, which makes xargs exec do_something_useful with only 1 file argument.

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This isn't quite what I was after, because there is no opportunity to do array-like things with the list, such as sorting: you must use each element as and when it appears out of the find command. If you could elaborate on this example, with the "do_something_useful" part being a bash array-push operation, then this might be what I'm after. –  Idris Jul 13 '09 at 12:33
This is what I use most if what I'm after is simple enough ;) –  mmmshuddup Jul 11 '13 at 17:41
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The main problem is, that the delimiter NUL (\0) is useless here, because it isn't possible to assign IFS a NUL-value. So as good programmers we take care, that the input for our program is something it is able to handle.

First we create a little program, which does this part for us:

printf "%s" "$@" | base64

...and call it base64str (don't forget chmod +x)

Second we can now use a simple and straightforward for-loop:

for i in `find -type f -exec base64str '{}' \;`
  file="`echo -n "$i" | base64 -d`"
  # do something with file

So the trick is, that a base64-string has no sign which causes trouble for bash - of course a xxd or something similar can also do the job.

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One must ensure that the part of the filesystem that find is processing does not change from when find is invoked until when the script completes. If this is not the case, a race condition results, which can be exploited to invoke commands on the wrong files. For instance a directory to be deleted (say /tmp/junk) could be replaced by a symlink to /home by an unprivaliged user. If the find command was running as root, and it was find -type d -exec rm -rf '{}' \;, this would delete all users' home folders. –  Demetri Sep 11 '13 at 23:23
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Yet another way of counting files:

find /DIR -type f -print0 | tr -dc '\0' | wc -c
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Here's an essay on how to properly handle filenames in shell, with lots of specifics:


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I think more elegant solutions exists, but I'll toss this one in. This will also work for filenames with spaces and/or newlines:

for f in *; do

You can then e.g. list the files one by one (in this case in reverse order):

for ((i = $i - 1; i >= 0; i--)); do
  ls -al "${array[$i]}"

This page gives a nice example, and for more see Chapter 26 in the Advanced Bash-Scripting Guide.

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This (and other similar examples below) is almost what I'm after - but with a big problem: it only works for globs of the current directory. I would like to be able to manipulate completely arbitrary lists of files; the output of "find" for example, which lists directories recursively, or any other list. What if my list was: ( /tmp/foo.jpg | /home/alice/bar.jpg | /home/bob/my holiday/baz.jpg | /tmp/new\nline/grault.jpg ), or any other totally arbitrary list of files (of course, potentially with spaces and newlines in them)? –  Idris Jul 13 '09 at 12:40
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You can safely do the count with this:

find . -exec echo ';' | wc -l

(It prints a newline for every file/dir found, and then count the newlines printed out...)

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Avoid xargs if you can:

man ruby | less -p 777 
#array=( $(find ~ -maxdepth 1 -type f -exec printf "%s\777" '{}' \; 2>/dev/null) ) 
array=( $(find ~ -maxdepth 1 -type f -exec printf "%s\777" '{}' + 2>/dev/null) ) 
echo ${#array[@]} 
printf "%s\n" "${array[@]}" | nl 
echo "${array[0]}" 
IFS=$' \t\n'
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Why do you set IFS to \777? –  sschober Feb 7 at 9:24
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I am new but I believe that this an answer; hope it helps someone:


declare -a array1

LISTING=`find $HOME/.fluxbox/styles/ -print0 -maxdepth 1 -type f`

array1=( `echo $LISTING`)
TAR_SOURCE=`echo ${array1[@]}`

#tar czvf ~/FluxieStyles.tgz $TAR_SOURCE
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This is similar to Stephan202's version, but the files (and directories) are put into an array all at once. The for loop here is just to "do useful things":

files=(*)                        # put files in current directory into an array
for file in "${files[@]}"
    echo "File ${i}: ${file}"    # do something useful 
    let i++

To get a count:

echo ${#files[@]}
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Bash has never been good at handling filenames (or any text really) because it uses spaces as a list delimiter.

I'd recommend using python with the sh library instead.

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