Category: Snippets

If you want to run some code on a directory, but maybe not always the same directory, then generating a menu can be very handy.

# The menu we are making looks like this
[me@parentfolder]$ directoryPicker $pwd
1) Subfolder_1
2) Subfolder_2
3) Subfolder_3
#? 

To make a generic menu, call select with an array, and it displays the choices. You can get complicated and have different return or output values for each of the choices but for this example, we are just setting a variable, DIRECTORY, which is returned to the calling function.

# The select function portion of the example
select dir in "${dirs[@]}"; do
  # This will be run only on the user's choice, the function itself 
  # handles displaying the array values as a menu
  DIRECTORY="${PARENT}/${dir}"
  break;
done

You can declare an array with values for each item under a directory by using a subshell to call ls.

# make an array using a directory listing
declare -a dirs=($(ls -d *))

# Want to check what is in here?  Echo all the entries with [*]
echo ${dirs[*]}

But you probably want to do a little filtering to remove files, since passing them to your calling function won’t do much and it makes the menu less readable.

# a basic array loop
for dir in "${dirs[@]}"; do
  echo ${dir}
done

To remove an item from an array, you want to unset that index, so you’re going to give this loop an index and increment the index using let.

index=0
for dir in "${dirs[@]}"; do
  if [ ! -d "${PARENT}/${dir}" ]; then
    # unset an array element by referencing the variable _name_, 
    # not using the variable. But the key will be the variable _value_ 
    # so you still have a $ in there.
    # e.g. array[1]
    unset 'dirs[$index]'
  fi
    
  # Incrementing a variable either requires arithmetic expansion with 
  # double parenthesis, or using let
  let "index++"
done

All put together, you get this handy function that takes a parent directory and returns a menu to choose only subdirectories.

# Fetch a list of directories under the passed one
# @param[1] parent directory
# @returns DIRECTORY, directory path
function directoryPicker {
  # $1 = Parent Directory
  PARENT=$1
  cd $PARENT

  # make an array using a directory listing
  declare -a dirs=($(ls -d *))
    
  # We want to display only folders as options, 
  # so remove non-directories
  index=0
  for dir in "${dirs[@]}"; do
    if [ ! -d "${PARENT}/${dir}" ]; then
      # unset an array element by referencing the variable name, 
      # not using the variable. But the key will be the variable value
      # e.g. array[1]
      unset 'dirs[$index]'
    fi
    
    # Incrementing a variable either requires arithmetic expansion with 
    # double parenthesis, or using let
    let "index++"
  done

  # Then display the array as a numbered choice list
  select dir in "${dirs[@]}"; do
    DIRECTORY="${PARENT}/${dir}"
    break;
  done
}

To put this select menu into use, you can call this function from inside another, passing it a parent directory. This example will fetch all the updates for all the git repos in a subfolder. I have my repos checked out into groups based on the organization or user that owns them, or based on a theme they have in common. So there are folders for my employer, my personal stuff, friends, and themed project topics like “WordPress” or “cryptocurrency”. So passing my updateRepos function a menu lets me update only a specific set of repos at once.

# Update all the repos under a parent folder
function updateRepos {
  # Get a list of subfolders, using our chooser to show a list
  directoryPicker "/Users/$(whoami)/Developer/github.com"
  REPOBASE=$DIRECTORY

  # Like we did in the chooser, create an array of subfolders
  cd $REPOBASE
  declare -a repos=($(ls -d *))

  # for each repo, fetch/pull latest
  for repo in "${repos[@]}"; do
    # Only bother with directories that have a .git subfolder
    if [[ -d $REPOBASE/${repo} && -d $REPOBASE/${repo}/.git ]]; then
      echo "Checking ${repo} for updates"
      cd $REPOBASE/${repo}
      git fetch
      git pull
    fi
  done
}