How can I read a list of filenames from a file in bash?

Question

I'm trying to write a bash script that will process a list of files whose names are stored one per line in an input file, something the likes of

find . -type f -mtime +15 > /tmp/filelist.txt
for F in $(cat /tmp/filelist.txt) ; do
  ...
done;

My problem is that filenames in filelist.txt may contain spaces, so the snipped above will expand the line

my text file.txt

to three different filenames, my, text and file.txt. How can I fix that?

Answer 1

I believe you can skip the temporary file entirely and just directly iterate over the results of find, i.e.:

for F in $(find . -type f -mtime +15) ; do
  ...
done;

No guarantees that my syntax is correct but I'm pretty sure the concept works.

Edit: If you really do have to process the file with a list of filenames and can't simply combine the commands as I did above, then you can change the value of the IFS variable--it stands for Internal Field Separator--to change how bash determines fields. By default it is set to whitespace, so a newline, space, or tab will begin a new field. If you set it to contain only a newline, then you can iterate over the file just as you did before.

Answer 2

Use read:

while read F  ; do
        echo $F
done </tmp/filelist.txt

Alternatively use IFS to change how the shell separates your list:

OLDIFS=$IFS
IFS="
"
for F in $(cat /tmp/filelist.txt) ; do
  echo $F
done
IFS=$OLDIFS

Alternatively (as suggested by @tangens), convert the body of your loop into a separate script, then use find's -exec option to run if for each file found directly.

Answer 3

use while read

echo $FILE | while read line
do
echo $line
done

You can do redirect instead of echo

Answer 4

I'm not a bash expert by any means ( I usually write my script in ruby or python to be cross-platform), but I would use a regex expration to escape spaces in each line before you process it.

For Bash Regex: http://www.linuxjournal.com/node/1006996

In a similar situation in Ruby ( processing a csv file, and cleaning up each line before using it):

File.foreach(csv_file_name) do |line| 
    clean_line = line.gsub(/( )/, '\ ') 
    #this finds the space in your file name and escapes it    
    #do more stuff here
end

Answer 5

You could use the -exec parameter of find and use the file names directly:

find . -type f -mtime +15 -exec <your command here> {} \;

The {} is a placeholder for the file name.

Answer 6

You can do this without a temporary file using process substitution:

while read F
do
  ...
done < <(find . -type f -mtime +15)

Answer 7

pipe your find command straight to while read loop

find . -type f -mtime +15 | while read -r line
do
   printf "do something with $line\n"
done