title: xargs rm -r with regex returns "no such directory"
body: <p>I have a folder with several subdirectories <code>b1_3, b1_4</code> etc. Inside these subdirectories I have some files and other subdirectories, and the names of these subdirs follow a pattern <code>alpha[digits]_etc</code>, as such</p>
  <pre><code>lfppfs@lfppfs:~$ ls -l Desktop/shape/PD_sigma4/b*
  
  Desktop/shape/PD_sigma4/b1_3:
  total 364
  drwxr-xr-x 2 lfppfs lfppfs 12288 ago  4 09:07 alpha0.0_b150_t10000_s5_qmat0.01
  drwxr-xr-x 2 lfppfs lfppfs 12288 ago  4 09:07 alpha0.0_b150_t10000_s5_qmat0.1
  -rwxr-xr-x 1 lfppfs lfppfs  1143 ago  4 09:07 alpha0.sh
  drwxr-xr-x 2 lfppfs lfppfs 12288 ago  4 09:07 alpha10.0_b150_t10000_s5_qmat0.01
  drwxr-xr-x 2 lfppfs lfppfs 12288 ago  4 09:07 alpha10.0_b150_t10000_s5_qmat0.1
  -rwxr-xr-x 1 lfppfs lfppfs  1144 ago  4 09:07 alpha10.sh
  -rwxr-xr-x 1 lfppfs lfppfs     7 ago  4 09:07 forbiden-sites.in
  -rwxr-xr-x 1 lfppfs lfppfs   984 ago  4 09:07 input0alpha0.in
  -rwxr-xr-x 1 lfppfs lfppfs   992 ago  4 09:07 input0alpha10.in
  
  Desktop/shape/PD_sigma4/b1_4:
  total 364
  drwxr-xr-x 2 lfppfs lfppfs 12288 ago  4 09:09 alpha0.0_b150_t10000_s5_qmat0.01
  drwxr-xr-x 2 lfppfs lfppfs 12288 ago  4 09:07 alpha0.0_b150_t10000_s5_qmat0.1
  -rwxr-xr-x 1 lfppfs lfppfs  1143 ago  4 09:07 alpha0.sh
  drwxr-xr-x 2 lfppfs lfppfs 12288 ago  4 09:07 alpha10.0_b150_t10000_s5_qmat0.01
  drwxr-xr-x 2 lfppfs lfppfs 12288 ago  4 09:07 alpha10.0_b150_t10000_s5_qmat0.1
  -rwxr-xr-x 1 lfppfs lfppfs  1144 ago  4 09:07 alpha10.sh
  -rwxr-xr-x 1 lfppfs lfppfs     7 ago  4 09:07 forbiden-sites.in
  -rwxr-xr-x 1 lfppfs lfppfs   984 ago  4 09:07 input0alpha0.in
  -rwxr-xr-x 1 lfppfs lfppfs   992 ago  4 09:07 input0alpha10.in
  </code></pre>
  <p>I want to delete only the subdirectories <code>alpha[digits]_etc</code> from all directories <code>b1_[digits]</code> (please note that there are also files called <code>alpha[digits].[digits].sh</code> which I don't want to delete). I've tried my luck with several commands, including</p>
  <p><code>ls Desktop/shape/PD_sigma4/b* | grep -P &quot;alpha\d*0\.0&quot; | xargs echo rm -r | bash</code></p>
  <p>But the shell returns</p>
  <pre><code>rm: cannot remove 'alpha0.0_b150_t10000_s5_qmat0.01': No such file or directory
  rm: cannot remove 'alpha0.0_b150_t10000_s5_qmat0.1': No such file or directory
  etc
  </code></pre>
  <p>Don't know what I'm doing wrong. Hope my question is clear.</p>
  <p><strong>EDIT</strong></p>
  <p>I also tried using <code>find Desktop/shape/PD_sigma4 -regextype posix-egrep -regex &quot;b\d_\d\/alpha\d*0\.0&quot; -delete</code> but then the shell returns all files inside <code>b1_[digits]</code>, including the ones I don't want to delete.</p>