I find myself frequently needing to create a new directory and changing to it enough to want to combine the two commands, so I figured it was a good opportunity to practice scripting with bash.
The command I use to create and change to a directory is mkdir -p directory_name && cd directory_name, and that's the command that the mkkdir function wraps, essentially. The only additional stuff that I would say is really consequential is the check to make sure that the name of the directory does not begin with a hyphen.
Also, the script explicitly checks to make sure the directory does not already exist. This is not something that mkdir does, and when I'm using this command combination, I'm usually trying to specifically create a new directory. I've accidentally modified files that I did not mean to because I mkdir -p && cd'd into a directory that already existed.
# mkkdir version 1.4.0
#
# Create a new directory and move into it in the same
# command.
#
# If the specified directory already exists, the command
# will fail, as the assumption is that the directory is
# meant to be new.
#
function mkkdir() {
# We begin by checking for the command-line argument
# passed in by the user. It must be exactly one, since
# we can only create and change into one directory, and
# all of the valid program options result in short-
# circuiting program execution.
#
if [[ $# -ne 1 ]]
then
# Since the number of command-line arguments was
# not exactly one, notify the user of their error
# and return with an error status code.
echo 'Usage: mkkdir <DirectoryPath>' >&2 && return 1
fi
# Check whether the user requested the version number
# of the program or the help menu.
case $1 in
-h | --help)
echo 'Usage: mkkdir <DirectoryPath>'
echo 'Create new directory and cd to it'
echo ''
echo ' -h, --help display this help and exit'
echo ' --version output version information and exit'
echo 'This is free software: you are free to change and redistribute it.'
echo 'There is NO WARRANTY, to the extent permitted by law.'
return 0
;;
--version)
echo 'mkkdir version 1.4.0'
return 0
;;
# Check for invalid options. This function will thus
# not be able to create directories that begin with a
# hyphen, but that's so uncommon so as to be totally
# fine.
#
# Usually an argument that begins with a hyphen
# detected here will almost always be a mispelled
# command-line option.
-* | --*)
echo "Invalid option detected: $1"
return 1
;;
esac
# Passing in an empty string to the function will not
# trigger any errors so far, since an argument was
# technically passed in. Still, this edge case is
# obviously not a valid use case, and we must therefore
# validate the input string.
if [ -z "$1" ]
then
# The input string is a zero-length string, so we
# simply let the user know and exit with an error
# status.
echo 'The empty string is an invalid directory path.' >&2 && return 1
fi
# Check whether the specified directory exists. If it
# does, return with an error status.
if [[ -d "$1" ]]
then
# The directory exists so simply let the user know
# and exit with an error status.
echo "The specified directory already exists: $1" >&2 && return 1
fi
# Finally, create the directory and change the current
# working directory to it using the cd command.
mkdir -p "$1" && cd "$1"
}
```
