Display files to size with lower and upper bound without using `find`

Question

I need to create a program via vim in Linux called between. The script takes two arguments as the lower bound and upper bound of the file size, and prints out a list of file names as well as their sizes. However, I can't use the find command to complete this script.

I have gotten this far: to display all the files; but I can't seem to display specific ones WITHOUT find.

#!/bin/bash

for i in *
do
    set -- $(ls -l "$i")
    echo $i: $5 bytes
done

Answer 1

for i in *
do
  size=$(stat --format="%s" "$i")
  if [ $size -gt $1 -a $size -lt $2 ]
  then
    printf "Right-sized: %s\n" "$i"
  else
    printf "Wrong-sized: %s\n" "$i"
  fi
done

This is just an update to your loop, but instead of parsing ls, it uses stat to gather the file's size, in bytes.

This snippet assumes that you've already sanity-checked $1 and $2 -- I didn't want to do all of your homework for you!

Answer 2

You could:

• To check for range you could use an if statement or a continue operation:

  if [[ $z -ge $1 || $z -le $2 ]]
  then
      : print result
  fi
  

  or

  [[ $z -lt $1 || $z -gt $2 ]] && continue
  : print result
  

• Depending on needs, the test options are:

  • -ge: Greater than or equal to
  • -le: Less than or equal to
  • -lt: Less than
  • -gt: Greater than

• Use stat, du or ls to get the size. The two latter would require a check to see if target is a directory or regular file as well:

  if [[ -f "$f" ]]
  then
      : a regular file
  fi
  

  or, to prevent nesting of if's:

  ! [[ -f "$f" ]] && continue
  

  with file sizes, for example, either of:

  z=$(stat -c%s "$f")
  z=$(du -b "$f" | cut -f1)
  z=$(ls -l "$f" | cut -d' ' -f5)
  

• To print the result you could use printf to get a more clean printout. I.e. fixed with of size etc. Also read this.

• If you really want to be nice, validate the arguments as well ...

---

#!/bin/bash

usage()
{
    printf "Usage: %s <min-size> <max-size>\n" "$0" >&2
    exit 1
}

! [[ "$1" =~ ^[0-9]+$ ]] && usage
! [[ "$2" =~ ^[0-9]+$ ]] && usage


for f in *
do
    z=$(stat -c%s "$f")

    # Alternatives to get size:
    # ! [[ -f "$f" ]] && continue
    # z=$(du -b "$f" | cut -f1)
    # z=$(ls -l "$f" | cut -d' ' -f5)

    if [[ $z -ge $1 || $z -le $2 ]]
    then
        printf "%11d %s\n" "$z" "$f"
    fi
done

Answer 3

What you need is a condition, which in shell has the following syntax:

if TEST
then
    ACTION
else
    ACTION
fi

For tests, it's common to employ [. For example, to check if $5 is greater than 25 but is less than 50, you'll write:

if [ "$5" -gt 25 ] && [ "$5" -lt 50 ]
then
    echo "It's greater than 25 but is less than 50"
else
    echo "It's either <= 25, or >= 50, or not a number at all"
fi

Don't forget the quotes (thanks @Wildcard for the reminder) and don't pass [ more than four arguments (thanks @Jeff Schaller for the link.)

Check out Bash Guide for Beginners and Advanced Bash Scripting Guide, they are a good reference.

(Note, though, that there are shells other than Bash, and their syntax and capabilities might differ.)