如何使用Shell脚本正确处理文件名

Question

I want to eval the latest filename inside my latest folder with some shell script. So im getting the latest folder name and the latest filename inside it:

latest_folder=$(ls -td */ | head -n 1)
echo $latest_folder
cd $latest_folder
latest_file="$(ls -t *$str | head -n 1)"
echo $latest_file

folder structure:

base_folder
    |
    |---000
    |     |---123.*
    |     |---124.*
    |     |---...
    |     |---999.*
    |
    |---001
    |     |---997.*
    |     |---998.*
    |     |---999.*

Where 001 is the latest folder. If the latest file inside this folder equals 999.* i need to create a new folder 002.

Anyone an idea?

Answer 1

Your thinking is not far off. I would advise against cd into the latest dire and simply use the same scheme to get the latest file in that folder by appending latest_folder/ with your command substitution.

Once you have the latest_file , you can simply use parameter expansion with substring removal to isolate the leading 3-digit number (eg filenum="${latest_file%%.*}" ). After than you can make your decision on whether a new directory is required based on filenum .

If you do need to create a new directory, then use can use printf -v to take advantage of the field-width modifier and '0' padding to format your new_folder names a 002 by simply adding 1 to the latest_folder number, eg printf -v new_folder "%03d" $((latest_folder + 1)) note: that is after removing the leading-zeros from latest_folder to prevent interpretation as Octal constants when adding 1 to get the new_folder number, eg $((latest_folder + 1)) .

Putting it altogether, you should be able to do something similar to:

#!/bin/bash

limit=999

latest_folder="$(ls -td */ | head -n 1)"                ## latest folder
latest_folder="${latest_folder:0:(-1)}"                 ## remove / at end
latest_file="$(ls -t "$latest_folder/" | head -n 1)"    ## latest file
filenum="${latest_file%%.*}"                            ## isolate ###
if ((filenum == limit)); then                           ## if ### = 999
    n=0
    while [ "${latest_folder:n:1}" = '0' ]; do          ## remove zeros
        latest_folder="${latest_folder:$((n+1))}"
        ((n++))
    done
    printf -v new_folder "%03d" $((latest_folder + 1))  ## new folder name
    mkdir -p new_folder                                 ## create new folder
fi

note: you should generally use find and sort to get the list of directories and filenames (using -maxdepth and -type to control the depth and type of file/dir searched for)

Let me know if you have questions.