Ttdfjt

Using the output of ls is generally unwise and unsafe - remember that both spaces and newlines and other shell meta-characters are valid characters in a file or directory name. It is possible to work around this problem in many cases, but doing so is usually more effort than just using the right tool for the job (i.e. find).

So, use find instead. For example:

find . -maxdepth 1 -type d ( -name here_is_a_dir -o -name here_is_another_one 
 -o -name yet_another_dir ) -exec tar cfz archive.tgz +

This finds any of the matching directories (-type d) in the current directory (.) and uses them as arguments to the tar command. The ( to ) is an expression where each of the sub-expressions are OR-ed together using -o (by default, find's predicates are AND-ed). i.e. it reads as "maxdepth 1 AND type directory AND (dir1 OR dir2 OR dir3)".

Note that without the brackets to force precedence, it would be interpreted as "maxdepth 1 AND type directory AND dir1 OR (dir2 OR dir3)", which would not return the full list of all existing directories. Mostly, it would return either nothing, or only dir3, depending on whether dir1 existed or not.

If you want it to find the sub-directories anywhere underneath the current directory, drop the -maxdepth 1 argument.

If you want the directory matches to be case-insensitive, use -iname instead of -name. Note that the argument to -name or -iname can be a pattern rather than a fixed string - this is useful if the desired directory names are very similar. e.g.

find . -maxdepth 1 -type d -iname 'dir[123]' -exec tar cfz archive.tgz +

The -exec .... works a lot like piping to xargs, but built in to find. In fact, you could use xargs if you wanted to by replacing everything from -exec onwards with -print0 | xargs -0 -r tar cfz archive.tgz. e.g.

find . -maxdepth 1 -type d -iname 'dir[123]' -print0 | 
 xargs -0 -r tar cfz archive.tgz 

(this uses a NUL character as the output separator, so it's as safe to use with dirnames that contain spaces etc as it is to use -exec. The -r option tells xargs to do nothing if there is no input)

With zsh:

dirs_to_archive=(some/dir /some/other/dir and/more/dirs)
existing_dirs=($^dirs_to_archive(/N))
if (($#existing_dirs)); then
 tar -cf - -- $existing_dirs | xz > file.tar.xz
else
 echo >&2 Error: none of the dirs were found
fi

The POSIX equivalent (though note that neither tar nor xz are POSIX commands) would be something like:

# The list of dirs in "$@" (the only array in POSIX sh language)
set -- some/dir /some/other/dir and/more/dirs

for dir do
 # remove from the array the elements that are not directories like with
 # zsh's / glob qualifier above
 [ -d "$dir" ] && [ ! -L "$dir" ] && set -- "$@" "$dir"
 shift
done
if [ "$#" -gt 0 ]; then
 tar -cf - -- "$@" | xz > file.tar.xz
else
 echo >&2 Error: none of the dirs were found
fi

If you can use bash, then with extended globbing (extglob):

$ shopt -s extglob; set -x
$ tar -czf archive.tgz *(here_is_a_dir|here_is_another_one|yet_another_dir)
+ tar -czf archive.tgz
tar: no files or directories specified

And if one or more of those exist:

$ touch here_is_a_dir yet_another_dir
+ touch here_is_a_dir yet_another_dir
$ tar -czvf archive.tgz *(here_is_a_dir|here_is_another_one|yet_another_dir)
+ tar -czvf archive.tgz here_is_a_dir yet_another_dir
a here_is_a_dir
a yet_another_dir

(I have used set -x so you can see the results of the glob expansion.)

This can be done relatively easily using ls to make a list of existing directories, and then piping through xargs into the tar command.

solution:

ls -d here_is_a_dir here_is_another_one yet_another_dir 2> /dev/null | xargs tar -czf archive.tgz

breakdown:

• 
  ls -d only list directories


• 
  here_is_a_dir here_is_another_one yet_another_dir the list of directories to check for


• 
  2> /dev/null pipe the stderr to /dev/null so we only get stdout output (no missing dirs)


• 
  | xargs turns the list of existing directories from the previous command into arguments


• 
  tar -czf archive.tgz make an archive using the arguments

One that should work with just POSIX sh (tar.sh):

#!/bin/sh

first=1
for dir in "$@"; do
 if [ "$first" ]; then # this is a bit ugly
 set --
 first=
 fi
 if [ -d "$dir" ]; then
 set -- "$@" "$dir"
 fi
done
echo tar -czf archive.tar.gz "$@" # remove that 'echo'

Test:

$ mkdir here_is_a_dir yet_another_dir
$ ./tar.sh here_is_a_dir here_is_another_one yet_another_dir
tar -czf archive.tar.gz here_is_a_dir yet_another_dir

If you have pax, you can use it to filter what gets included in the archive. Pax is mandated by POSIX as a replacement for the historically diverse cpio and tar, but many Unix variants have resisted its adoption, and in particular BusyBox doesn't have it.

Pax has a file exclusion feature, even though it's rather hidden in the description. You can rename files with -s. If you rename a file to the empty string, it gets excluded. With multiple -s options, for each the first match applies and renaming -s filters are skipped. This way, you can build a series of include/exclude rules, much like with rsync. An include rule in Pax syntax is -s'!REGEX!&!' (rename to itself) and an exclude rule is -s'!REGEX!!' (rename to empty).

pax -w -x ustar 
 -s'!^./here_is_a_dir$!&!' -s'!^./here_is_a_dir/!&!' 
 -s'!^./here_is_another_one$!&!' -s'!^./here_is_another_one/!&!' 
 -s'!^./yet_another_dir$!&!' -s'!^./yet_another_dir/!&!' 
 . | gzip >archive.tgz

BSD tar has a similar -s option. On the other hand, GNU tar and BusyBox tar don't have any way to do this include/exclude gymnastics.

Simplest is probably

find adir anotherdir yadir -maxdepth 0 2>&- | tar Tcf - my.tar

If your version of tar supports it, create an empty tar file, and append to it as necessary using -r instead of -c

touch foo.tar

for d in here_is_a_dir here_is_another_one yet_another_dir; do
 if [ -d "$d" ]; then
 tar -rf foo.tar "$d"
 fi
done
gzip foo.tar