Initial data commit

Task/Find-common-directory-path/REXX/find-common-directory-path.rexx

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+/*REXX program  finds  the  common directory path  for a list of files.       */
+/* original code: Gerard Schildberger                                         */
+/* 20230606 Walter Pachl refurbisher adn improved (file.4 = 'home' -> /)      */
+file.  = ''                            /*the default for all file lists (null)*/
+file.1 = '/home/user1/tmp/coverage/test'
+        /*123456789.123456789.123456768*/
+file.2 = '/home/user1/tmp/covert/operator'
+file.3 = '/home/user1/tmp/coven/members'
+
+L=length(file.1)                       /*use the length of the first string.  */
+Do j=2 While file.j\==''               /*loop for the other file names        */
+  diffp=compare(file.j,file.1)         /*find the first different character   */
+  If diffp>0 Then Do                   /*Strings are different                */
+    L=min(L,diffp)                     /*get the minimum length equal strings.*/
+    If right(file.j,1)<>'/' Then Do    /*not a directory                      */
+     L=lastpos('/',left(file.j,L))     /* go back to directory end            */
+      If L=0 Then Do
+        Say 'common directory path: /'
+        Exit
+        End
+      End
+    End
+  End
+common=left(file.1,lastpos('/',file.1,L)) /*determine the shortest DIR string.*/
+If right(common,1)=='/' Then           /* remove the trailing /               */
+  common=left(common,length(common)-1)
+If common=='' then common= "/"         /*if no common directory, assume home. */
+Say 'common directory path: 'common
+                                       /*stick a fork in it,  we're all done. */