bash script for settings permissions on directory and files

Question

Could you help me to create bash script to: Set the permissions in the directory that is the argument of the script for all files that have a defined extension as the second script argument to values that are defined as the third argument of the script.

Answer 1

Since you're probably new to bash and parsing arguments passed to scripts, I'll show you a rudimentary way to accomplish what you are describing.

#!/bin/bash

# stop execution of the script if an error occurs suchs as when the 
# directory in argument 1 does not exists
set -e 

dir=$1 # get the directory from the first argument
ext=$2 # get the extension from the second argument
perms=$3 # the third argument is the permissions you're going to pass to `chmod`

cd "$dir" # change directory to the target directory

# use regular filename expansion with the extension in 
# $ext and supply `chmod` with the permissions in $perms
chmod "$perms" *"$ext" 

If you saved this as extchmod.sh and made it executable, you would run it like this:

$ ./extchmod.sh target_directory .txt 644
$ ./extchmod.sh target_directory .sh 755

which would change all files in target_directory with a .txt extensions to permissions 644 and all files with a .sh extension to permissions 755.

I should note that in bash/sh, $1 has the value of the first argument, $2 has the value of the second argument, and so on. $@ will always be an array containing all of the arguments.

Answer 2

I would recommend using a combination of find and xargs

• Directory: /home/mirko/example/
• Fileextension: .jpg
• Mode for files: 644

$ find /home/mirko/example/ -maxdepth 1 -name '*.jpg' -print0 | xargs -0 chmod 644

If you still want a shell script for that, I would suggest something like:

#!/usr/bin/env bash

scriptname=$(basename $0)

if [ $# -ne 3 ]; then
    echo "usage: $scriptname path extension mode" >&2
    echo "example: $scriptname /home/foo/pictures/ jpg 644" >&2
    exit 1
fi

directory=$1
extension=$2
mode=$3

find "$directory" -maxdepth 1 -name "*.${extension}" -print0 | xargs -0 chmod "$mode"

if [ $? -ne 0 ]; then
    echo "$scriptname: ERROR: command returned unsuccesfull" >&2
    exit 1
fi