Implementing linked list in shell scripting Post: 302994942

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Top Forums Shell Programming and Scripting Implementing linked list in shell scripting Post 302994942 by Chubler_XL on Wednesday 29th of March 2017 05:16:45 PM

03-29-2017

Moderator

I'd use arrays. One for the values and one for the next index.

Here is an example of a sorted linked list:

Code:

llinsert() {
   local END=${#LST[@]}
   local i

   for((i=0; NXT[i]; i=NXT[i]))
   do
     if [ "${LST[NXT[i]]}" \> "$1" ]
     then
        ((i=NXT[i]))
        LST[END]=${LST[i]}
        LST[i]="$1"
        ((NXT[END]=NXT[i]))
        ((NXT[i]=END))
        return
     fi
   done

   LST[END]="$1"
   ((NXT[i]=END))
   NXT[END]=0
}

llfirst() {
  pos=NXT[0]
  echo "${LST[pos]}"
}

llnext() {
   (( NXT[pos] )) && {
       ((pos=NXT[pos]))
       echo "${LST[pos]}"
   }
}

LST=("")

llinsert "please"
llinsert "sort"
llinsert "this"
llinsert "small"
llinsert "list"
llinsert "of"
llinsert "words"

llfirst
while llnext
do
  :
done

# Debug - Output array contents
echo
printf "%-4s %-8s %-3s\n" Idx LST NXT
printf "%-4s %-8s %-3s\n" --- -------- ---
for((i=0;i<${#NXT[@]};i++)) {
   printf "%-4s %-8s %-3s\n" "$i" "${LST[i]}" "${NXT[i]}"
}

Output:

Code:

list
of
please
small
sort
this
words

Idx  LST      NXT
---  -------- ---
0             1  
1    list     5  
2    small    4  
3    this     7  
4    sort     3  
5    of       6  
6    please   2  
7    words    0

Last edited by Chubler_XL; 03-29-2017 at 06:27 PM..

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modperl::global

apache_mod_perl-108~358::mod_perl-2.0.7::docs::api::ModPUser:Contributed Perapache_mod_perl-108~358::mod_perl-2.0.7::docs::api::ModPerl::Global(3)

NAME

       ModPerl::Global -- Perl API for manipulating special Perl lists

Synopsis
	 use ModPerl::Global ();
	 my $package = 'MyApache2::Package';

	 # make the END blocks of this package special
	 ModPerl::Global::special_list_register(END => $package);

	 # Execute all encoutered END blocks from this package now
	 ModPerl::Global::special_list_call(	END => $package);

	 # delete the list of END blocks
	 ModPerl::Global::special_list_clear(	END => $package);

Description
       "ModPerl::Global" provides an API to manipulate special perl lists. At the moment only the "END" blocks list is supported.

       This API allows you to change the normal Perl behavior, and execute special lists when you need to.

       For example "ModPerl::RegistryCooker" uses it to run "END" blocks in the scripts at the end of each request.

       Before loading a module containing package $package, you need to register it, so the special blocks will be intercepted by mod_perl and not
       given to Perl. "special_list_register" does that. Later on when you want to execute the special blocks, "special_list_call" should be
       called. Unless you want to call the list more than once, clear the list with "special_list_clear".

API

       "ModPerl::Global" provides the following methods:

   "special_list_call"
       Call the special list

	 $ok = special_list_call($key => $package);

       arg1: $key ( string )
	   The name of the special list. At the moment only 'END' is supported.

       arg2: $package ( string )
	   what package to special list is for

       ret: $ok ( boolean )
	   true value if $key is known, false otherwise.

       since: 2.0.00

   "special_list_clear"
       Clear the special list

	 $ok = special_list_clear($key => $package);

       arg1: $key ( string )
	   The name of the special list. At the moment only 'END' is supported.

       arg2: $package ( string )
	   what package to special list is for

       ret: $ok ( boolean )
	   true value if $key is known, false otherwise.

       since: 2.0.00

   "special_list_register"
       Register the special list

	 $ok = special_list_call($key => $package);

       arg1: $key ( string )
	   The name of the special list. At the moment only 'END' is supported.

       arg2: $package ( string )
	   what package to special list is for

       ret: $ok ( boolean )
	   true value if $key is known, false otherwise.

       since: 2.0.00

       Notice that you need to register the package before it is loaded. If you register it after, Perl has already compiled the "END" blocks and
       there are no longer under your control.

See Also
       mod_perl 2.0 documentation.

Copyright
       mod_perl 2.0 and its core modules are copyrighted under The Apache Software License, Version 2.0.

Authors
       The mod_perl development team and numerous contributors.

perl v5.16.2							    2011-02-apache_mod_perl-108~358::mod_perl-2.0.7::docs::api::ModPerl::Global(3)