How to concatenate two strings to build a complete path - linux

Question

I am trying to write a bash script. In this script I want user to enter a path of a directory. Then I want to append some strings at the end of this string and build a path to some subdirectories.
For example assume user enters an string like this:
/home/user1/MyFolder
Now I want to create 2 subdirectories in this directory and copy some files there.
/home/user1/MyFolder/subFold1
/home/user1/MyFolder/subFold2
How can I do this?

Answer 1

The POSIX standard mandates that multiple / are treated as a single / in a file name. Thus
//dir///subdir////file is the same as /dir/subdir/file.
As such concatenating a two strings to build a complete path is a simple as:
full_path="$part1/$part2"

Answer 2

#!/bin/bash
read -p "Enter a directory: " BASEPATH
SUBFOLD1=${BASEPATH%%/}/subFold1
SUBFOLD2=${BASEPATH%%/}/subFold2
echo "I will create $SUBFOLD1 and $SUBFOLD2"
# mkdir -p $SUBFOLD1
# mkdir -p $SUBFOLD2
And if you want to use readline so you get completion and all that, add a -e to the call to read:
read -e -p "Enter a directory: " BASEPATH

Answer 3

Won't simply concatenating the part of your path accomplish what you want?
$ base="/home/user1/MyFolder/"
$ subdir="subFold1"
$ new_path=$base$subdir
$ echo $new_path
/home/user1/MyFolder/subFold1
You can then create the folders/directories as needed.
One convention is to end directory paths with / (e.g. /home/) because paths starting with a / could be confused with the root directory. If a double slash (//) is used in a path, it is also still correct. But, if no slash is used on either variable, it would be incorrect (e.g. /home/user1/MyFoldersubFold1).

Answer 4

The following script catenates several (relative/absolute) paths (BASEPATH) with a relative path (SUBDIR):
shopt -s extglob
SUBDIR="subdir"
for BASEPATH in '' / base base/ base// /base /base/ /base//; do
echo "BASEPATH = \"$BASEPATH\" --> ${BASEPATH%%+(/)}${BASEPATH:+/}$SUBDIR"
done
The output of which is:
BASEPATH = "" --> subdir
BASEPATH = "/" --> /subdir
BASEPATH = "base" --> base/subdir
BASEPATH = "base/" --> base/subdir
BASEPATH = "base//" --> base/subdir
BASEPATH = "/base" --> /base/subdir
BASEPATH = "/base/" --> /base/subdir
BASEPATH = "/base//" --> /base/subdir
The shopt -s extglob is only necessary to allow BASEPATH to end on multiple slashes (which is probably nonsense). Without extended globing you can just use:
echo ${BASEPATH%%/}${BASEPATH:+/}$SUBDIR
which would result in the less neat but still working:
BASEPATH = "" --> subdir
BASEPATH = "/" --> /subdir
BASEPATH = "base" --> base/subdir
BASEPATH = "base/" --> base/subdir
BASEPATH = "base//" --> base//subdir
BASEPATH = "/base" --> /base/subdir
BASEPATH = "/base/" --> /base/subdir
BASEPATH = "/base//" --> /base//subdir

Answer 5

I was working around with my shell script which need to do some path joining stuff like you do.
The thing is, both path like
/data/foo/bar
/data/foo/bar/
are valid.
If I want to append a file to this path like
/data/foo/bar/myfile
there was no native method (like os.path.join() in python) in shell to handle such situation.
But I did found a trick
For example , the base path was store in a shell variable
BASE=~/mydir
and the last file name you wanna join was
FILE=myfile
Then you can assign your new path like this
NEW_PATH=$(realpath ${BASE})/FILE
and then you`ll get
$ echo $NEW_PATH
/path/to/your/home/mydir/myfile
the reason is quiet simple, the "realpath" command would always trim the terminating slash for you if necessary

Answer 6

This should works for empty dir (You may need to check if the second string starts with / which should be treat as an absolute path?):
#!/bin/bash
join_path() {
echo "${1:+$1/}$2" | sed 's#//#/#g'
}
join_path "" a.bin
join_path "/data" a.bin
join_path "/data/" a.bin
Output:
a.bin
/data/a.bin
/data/a.bin
Reference: Shell Parameter Expansion

Answer 7

I ended up concating all arguments ($*) with '/' (IFS=/ - Internal Field Separator) as separator and then removing all repeating '/' (tr -s /).
My function looks like this:
join_paths() {
(IFS=/; echo "'$*'" | tr -s /)
}

Answer 8

#Dunes' basic solution, but accounting for empty strings:
[ -z "$rootpath" ] && rootpath="."
fullpath="${rootpath}/${subdir}"