I am working on a command to move the x number of oldest files(FIFO) into a directory, is it better idea to pipe the "find" result into "ls" or just use the "ls" .. please suggest.

ls -ltr `/bin/find ${in}/* -prune -name "*.txt"  -type f` | head -10 |     

 while read -r infile ; do                    

     -move the file 

done

or should i just use ls.
the reason i am using find is: i read some online content that ls should be avoided in scripting. but in my code at the end i have to pipe the find results into the ls.
i am worried if find result is too big would it might cause any problem.

While perl is probably going to be faster than looping through a large directory "x" times, here's a brute force simple solution.

The outer loop determines how many files will be moved -- 3 in this example. Inside that loop, we initialize an "oldest" file to the first filename that results from globbing *. The inner loop then compares every file's timestamp to see if it is older than (-ot) the currently-oldest file. If it is, we update the "oldest" filename. At the end of the inner loop, we report and move that file.

for((count=0; count < 3; count++))

do

  set -- *

  oldest=$1

  for f in ./*

  do

    if [ "$f" -ot "$oldest" ]

    then

      oldest=$f

    fi

  done

  echo mv -- "$oldest" ./.archive

  mv -- "$oldest" ./.archive

done

Python heapq.nsmallest

bash:

find -printf '%T@ %pn' |

python noldest.py 1000 |

xargs -Ixxx mv xxx directory_for_old_files

Here find command lists files in format "seconds from 1970 (%T@), space, filename (%p)". Trailing xargs command takes filenames from stdin one by one and applies mv xxx directory_for_old_files command substituting xxx with them.

noldest.py implementation could be:

import sys

from heapq import nsmallest

from datetime import datetime





n = int(sys.argv[1])

date_file_pairs = (line.split(' ', maxsplit=1) for line in sys.stdin)  # generators are lazy



def parse_date(date_and_filename):

    seconds_from_1970 = float(date_and_filename[0])

    return datetime.fromtimestamp(int(seconds_from_1970))



for _, filename in nsmallest(n, date_file_pairs, key=parse_date):

    print(filename.rstrip('n'))  # lines in sys.stdin have trailing newlines

The perfomance depends on implementation of nsmallest algorithm from python standard library.