How to create a FOR loop in BASH that lists files in a certain format

Question

I want to print all the files in my chosen directory. I want to format the files to be displayed under the column headers. But when I'm trying to run the below code I'm getting errors in the console.

list_files()
{   
    FILES=/home/student/.junkdir/
    echo "Listing files in Junk Directory"
    format="%8s%10s%10s   $-s\n"
    printf "$format" "Filename" "Size(Bytes)" "Type"
    printf "$format" "--------" "-----------" "----"
    for listed_file in $FILES; do
        file_name=$(du $listed_file | awk '{print $2}')
        file_size=$(du $listed_file | awk '{print $1}')
        file_type=$(file $listed_file | cut -d ' ' -f2-)
        printf "$format" $file_name $file_size $file_type
    done
}

This is the output

Listing files in Junk Directory
FilenameSize(Bytes)      Type   hBs
-------------------      ----   hBs
du: cannot access ‘/home/student/.junkdir/*’: No such file or directory
du: cannot access ‘/home/student/.junkdir/*’: No such file or directory
ERROR:    cannot      open   hBs
`/home/student/.junkdir/*'       (No      such   hBs
file        ordirectory)   hBs

Did you edit the script when posting it? The error messages lead me to think your for loop is actually for listed_file in $FILES/* with a wildcard. — John Kugelman
– John Kugelman, Commented Oct 17, 2017 at 16:32
Yes sorry, my original code had the wildcard. I think I've realised part of my problem. — Chris Daly
– Chris Daly, Commented Oct 17, 2017 at 16:36
See here: cyberciti.biz/faq/bash-for-loop FILES is not what you think it is. — user1531971
– user1531971, Commented Oct 17, 2017 at 16:36
I didn't actually have any files in the .junkdir yet. Now that I've added the wildcard again, I am getting more success — Chris Daly
– Chris Daly, Commented Oct 17, 2017 at 16:37

glenn jackman · Accepted Answer · 2017-10-17 16:31:41Z

1

Use the stat command to get the data, and column to make the output pretty.

stat -c $'%n\t%s\t%F' * | column -ts $'\t'

In a function

list_files() {   
    local dir=/home/student/.junkdir/
    echo "Listing files in Junk Directory"
    {
        printf "%s\t%s\t%s\n" "Filename" "Size(Bytes)" "Type"
        stat -c $'%n\t%s\t%F' "$dir"/*
    } | column -t -s $'\t'
}

answered Oct 17, 2017 at 16:31

glenn jackman

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4 Comments

Chris Daly Over a year ago

Could you advise how to use this method using the same commands I have in my example? I've tried it myself but not having any joy.

glenn jackman Over a year ago

You only need to call du once: read -r filesize filename < <(du "$listed_file")

glenn jackman Over a year ago

files are allowed to have spaces and colons, so I would use substrings to chop off the name from the file output: output=$(file "$listed_file"); filetype=${output:${#listed_file}+2}

glenn jackman Over a year ago

The <(...) is a process substitution. For the substring stuff, see parameter expansion

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