Diff for "BashFAQ/010"

How can I recreate a directory hierarchy structure, without the files?

With the cpio program:

   1 cd -- "$srcdir" &&
   2 find . -type d -print | cpio -dumpv -- "$dstdir"

or with the pax program:

   1 cd -- "$srcdir" &&
   2 find . -type d -print | pax -rwdv -- "$dstdir"

or with GNU tar, and more verbose syntax:

   1 cd -- "$srcdir" &&
   2 find . -type d -print | tar c --files-from - --no-recursion |
   3   tar x --directory "$dstdir"

This creates a list of directory names with find, non-recursively adds just the directories to an archive, and pipes it to a second tar instance to extract it at the target location. As you can see, tar is the least suited to this task, but people just adore it, so it has to be included here to appease the tar fanboy crowd. (Note: you can't even do this at all with a typical Unix tar. Also note: there is no such thing as "standard tar", as both tar and cpio were intentionally omitted from POSIX in favor of pax.)

All the solutions above will fail if directory names contain newline characters. On many modern BSD/GNU systems, at least, they can be trivially modified to cope with that, by using find -print0 and one of pax -0 or cpio -0 or tar --null (check your system documentation to see which of these commands you have, and which extensions are available). If you really don't have access to those options, you can probably, at least, use ! -path $'*\n*' -type d -print, or better -name $'*\n*' -prune -o -type d -print (instead of -type d -print) to ignore directories that contain newline characters in their path, making sure find is run in the C/POSIX locale to also exclude file paths containing newline characters as well as sequence of bytes not forming valid characters in the user's locale.

with find

   1 export dstdir
   2 mkdir -p -- "$dstdir" &&
   3 cd -- "$srcdir" &&
   4 find . -type d -exec sh -c \
   5   'cd -- "$dstdir" && mkdir -- "$@"' sh {} +

or with bash 4's globstar

   1 shopt -s globstar nullglob &&
   2 cd -- "$srcdir" && dirs=(**/) && (( ${#dirs[@]} )) &&
   3 cd -- "$dstdir" && mkdir -- "${dirs[@]}"

(though beware that will also copy symlinks to directories as directories; older versions of bash would also traverse symlinks when crawling the directory tree).

or with zsh's recursive globbing and glob qualifiers:

   1 export srcdir dstdir
   2 zsh -ec '
   3 cd -- "$srcdir"
   4 dirs=(**/*(/D))
   5 cd -- "$dstdir"
   6 mkdir -- $dirs'

If you want to create stub files instead of full-sized files, the following is likely to be the simplest solution. The find command recreates the regular files using "dummy" files (empty files with the same timestamps):

   1 cd -- "$srcdir" &&
   2 DSTDIR=$dstdir find . -type f -exec sh -c \
   3   'for i do touch -r "$i" -- "$DSTDIR/$i"; done' sh {} +

If your find can't handle -exec + then you can use \; instead of + at the end of the command. See UsingFind for explanations.

CategoryShell