Bash Script - iterating over output of find

Question

I have a bash script in which I need to iterate over each line of the ouput of the find command, but it appears that I am iterating over each Word (space delimited) from the find command. My script looks like this so far:

folders=`find -maxdepth 1 -type d`

for $i in $folders
do
    echo $i
done

I would expect this to give output like:

./dir1 and foo
./dir2 and bar
./dir3 and baz

But I am insted getting output like this:

./dir1
and
foo
./dir2
and
bar
./dir3
and
baz

What am I doing wrong here?

See also answer #1 in mywiki.wooledge.org/BashPitfalls

Charles Duffy
– Charles Duffy

2014-02-09 18:44:03 +00:00
Commented Feb 9, 2014 at 18:44 — Charles Duffy
– Charles Duffy, Commented Feb 9, 2014 at 18:44

Charles Duffy · Accepted Answer · 2014-02-09 18:42:22Z

28

folders=`foo`

is always wrong, because it assumes that your directories won't contain spaces, newlines (yes, they're valid!), glob characters, etc. One robust approach (which requires the GNU extension -print0) follows:

while IFS='' read -r -d '' filename; do
  : # something with "$filename"
done < <(find . -maxdepth 1 -type d -print0)

Another safe and robust approach is to have find itself directly invoke your desired command:

find . -maxdepth 1 -type d -exec printf '%s\n' '{}' +

See the UsingFind wiki page for a complete treatment of the subject.

edited Feb 9, 2014 at 18:42

answered Feb 9, 2014 at 18:36

Charles Duffy

299k43 gold badges441 silver badges496 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Gordon Davisson Over a year ago

Note that the find ... -exec form only works for normal commands -- if you want to use shell builtins, shell functions, compound commands, etc you need to use either the while ... done approach or the for loop chepner suggested.

Charles Duffy Over a year ago

@GordonDavisson Generally true. However, the UsingFind wiki page (linked in my answer) describes using -exec bash -c '...' _ {} +, which allows shell builtins and the like to be used.

Seneral Over a year ago

Warning! Some commands, including ffmpeg, will read from stdin, and confuse the "read" command used in the loop. Symptoms are beginnings of the filename being cut off (=> invalid names). You need to disable this behaviour in the command that reads from stdin, two solutions here: stackoverflow.com/a/21634699

chepner · Accepted Answer · 2014-02-09 18:39:48Z

7

Since you aren't using any of the more advanced features of find, you can use a simple pattern to iterate over the subdirectories:

for i in ./*/; do
    echo "$i"
done

answered Feb 9, 2014 at 18:39

chepner

538k77 gold badges594 silver badges746 bronze badges

1 Comment

Sarfraaz Ahmed Over a year ago

Most answers talk about using while. But, I was trying to find a solution that involved only a for loop and your solution works great. My scenario was to fetch filename from a different folder. So, added a small change to this : (cd $folder; for i in ./*/; do echo "$i"; done). Created a subshell, for running this on my shell without having to change folder paths

Малъ Скрылевъ · Accepted Answer · 2014-02-09 19:34:41Z

3

You can do something like this:

find -maxdepth 1 -type d | while read -r i
do
    echo "$i"
done

edited Feb 9, 2014 at 19:34

answered Feb 9, 2014 at 18:39

Малъ Скрылевъ

16.5k5 gold badges59 silver badges74 bronze badges

15 Comments

Charles Duffy Over a year ago

Unsafe. Doesn't correctly handle filenames containing backslash sequences, newlines, runs of multiple whitespace characters, etc.

Малъ Скрылевъ Over a year ago

@CharlesDuffy fixed and checked both ``, and whitespaces

Charles Duffy Over a year ago

...better -- with the -r you've handled backslash sequences, but you're still expanding globs, compressing runs of whitespace into a single character, and stripping trailing whitespace.

Малъ Скрылевъ Over a year ago

@CharlesDuffy how to check it? I've checked two whitespace, it handles that

Charles Duffy Over a year ago

Checked how? The problem you still have here is two spaces directly in a row, not two spaces anywhere in the filename.

|

ChrisoLosoph · Accepted Answer · 2024-03-02 23:26:48Z

Based on Charles Duffy's answer (kudos!), I made a bash function qfind (quoted find) which outputs all the output of find but quoted. I am adding it to my .bashrc

qfind() {
    while IFS='' read -r -d $'\0' findOutput; do
        /usr/bin/echo -n "${findOutput@Q} "
    done < <(/usr/bin/find "$@" -print0)
}

The quoted strings are separated with whitespace. ${findOutput@Q} expands to the quoted value of ${findOutput} like "$(quote "$findOutput")". When -n is removed from echo, it will also use newline characters for separation.

It can be used like this

eval "folders=($(qfind . -maxdepth 1 -type d))"
for i in "${folders[@]}"; do
    echo "$i"
done

eval is required to evaluate any quoted substrings.

With the predefined function, there won't be any additional commands in the loop body that read characters away from stdin during the loop.

Collectives™ on Stack Overflow

Bash Script - iterating over output of find

4 Answers 4

3 Comments

1 Comment

15 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

3 Comments

1 Comment

15 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related