How to go to each directory and execute a command?

Question

How do I write a bash script that goes through each directory inside a parent_directory and executes a command in each directory

Answer 1

While one liners are good for quick and dirty usage, I prefer below more verbose version for writing scripts. This is the template I use which takes care of many edge cases and allows you to write more complex code to execute on a folder. You can write your bash code in the function dir_command. Below, dir_coomand implements tagging each repository in git as an example. Rest of the script calls dir_command for each folder in directory. The example of iterating through only given set of folder is also include.

#!/bin/bash

#Use set -x if you want to echo each command while getting executed
#set -x

#Save current directory so we can restore it later
cur=$PWD
#Save command line arguments so functions can access it
args=("$@")

#Put your code in this function
#To access command line arguments use syntax ${args[1]} etc
function dir_command {
    #This example command implements doing git status for folder
    cd $1
    echo "$(tput setaf 2)$1$(tput sgr 0)"
    git tag -a ${args[0]} -m "${args[1]}"
    git push --tags
    cd ..
}

#This loop will go to each immediate child and execute dir_command
find . -maxdepth 1 -type d \( ! -name . \) | while read dir; do
   dir_command "$dir/"
done

#This example loop only loops through give set of folders    
declare -a dirs=("dir1" "dir2" "dir3")
for dir in "${dirs[@]}"; do
    dir_command "$dir/"
done

#Restore the folder
cd "$cur"