Thread: Really basic string operation

I am having a little trouble in writing a sort function! ...I need to sort an array containing file / directory names for my personal ls command. At the moment, it sorts the array into alphabetical order, which is perfect, however, if i then add the switch -a the program ouputs all files beginning with . alphabetically and then all files with no leading . alphabetically, example:

Code:

[root@localhost shell]# ./myls -la /tmp
list of contents for: /tmp
-rwxrwxrwx     13 root     root          4096 Sun Nov 27 21:53:55 2005 .
-rwxr-xr-x     20 root     root          4096 Sun Nov 27 20:06:26 2005 ..
-rwx------      1 root     nobody           0 Sun Nov 27 20:07:26 2005 .fam_socket
-rwxrwxrwx      2 xfs      xfs           4096 Sun Nov 27 20:06:59 2005 .font-unix
-rw-rw-rw-      1 root     root             0 Sun Nov 27 20:07:01 2005 .gdm_socket
-rwxrwxrwx      2 root     root          4096 Sun Nov 27 20:07:24 2005 .ICE-unix
-r--r--r--      1 root     root            11 Sun Nov 27 20:07:01 2005 .X0-lock
-rwxrwxrwx      2 root     root          4096 Sun Nov 27 20:07:01 2005 .X11-unix
-rwx------      2 root     root          4096 Wed Nov  9 16:57:21 2005 mcop-root
-rwx------      2 matt     matt          4096 Tue Nov  8 21:12:41 2005 orbit-matt
-rwx------      2 root     root         12288 Sun Nov 27 20:08:50 2005 orbit-root
-rwx------      2 root     root          4096 Mon Nov 21 18:08:18 2005 plugtmp
-rwx------      2 root     root          4096 Fri Nov 25 12:27:53 2005 plugtmp-1
-rwx------      2 root     root          4096 Sun Nov 27 21:16:46 2005 plugtmp-2
-rwx------      2 root     root          4096 Mon Nov  7 13:35:34 2005 ssh-XX9iLygl
-rwx------      2 root     root          4096 Sun Nov 27 20:07:23 2005 ssh-XXNXMs4V

Basically, i need to add to my sort compare function an operation that ignores leading dots when sorting, but also a way to put the leading dots back onto the names once sorting is complete!!!

Does anyone know how to ignore the leading char when copying or comparing a string, because i cannot find it anywhere!

Code:

/**********************************************************************************************/
/**                                                                                          **/
/** FUNCTION           : sortCompare                                                         **/
/** DESCRIPTION        : function to compare 2 strings and returns an integer less than,     **/
/**                      equal to, or greater than zero if str1 is found, respectively, to   **/
/**                      be less than, to mathc, or be greater than str2.                    **/
/**                      NOTE: This function ignores leading zeros and case                  **/
/** PARAMETERS         : a pointer to the first string to be compared                        **/
/**                      a pointer to the second string to be compared                       **/
/** AUTHOR             : Matt Conway (03500546)                                              **/
/** DATE               : 21/11/2005                                                          **/
/**                                                                                          **/
/**********************************************************************************************/
int sortCompare(const void *str1, const void *str2){

  char tmpStr1[strlen(str1)];
  char tmpStr2[strlen(str2)];

  /* Check to see if str1 name is not . */
  if (!strcmp(str1, ".") == 0){
    /* so check for leading zero on str1 */
    if (strncmp(str1, ".", 1) == 0){
      /* copy str1 to tmpStr1 ignoring leading . */
    }    
  }
  /* DO THE SAME FOR str2 */

  /* return the result of the copy */
  return strcasecmp(str1,str2);

}

I know that the dynamic array assignment is bad programming, but i will change this to malloc space once it is in working order!!!!!!

Thanks for any ideas or hints!!!!

Something like

Code:

int sortCompare(const void *str1, const void *str2){
  const char *p1 = str1;
  const char *p2 = str2;
  if ( *p1 == '.' ) {
    if ( *p2 == '.' ) {
      return strcmp ( p1, p2 );
    } else {
      return -1;  /* any dot comes before any non-dot */
    }
  } else
  if ( *p2 == '.' ) {
    /* something similar */
  } else {
    return strcmp ( p1, p2 );
  }
}

Code:

/* if both strings have leading '.'s */
return strcmp( &((char *)name1)[1], &((char *)name2)[1]);

No need for copying.

And just use conditions similar to Salems to determine what you need to return.

Basically, i need to add to my sort compare function an operation that ignores leading dots when sorting, but also a way to put the leading dots back onto the names once sorting is complete!!!

Code:

int sortCompare(const void *str1, const void *str2){
  const char *p1 = str1;
  const char *p2 = str2;
  if ( *p1 == '.' )
    P1++;
  if ( *p2 == '.' )
    p2++;
  return strcmp ( p1, p2 );
}