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Full Discussion: bash: How to reuse the search result of "find"
Top Forums Shell Programming and Scripting bash: How to reuse the search result of "find" Post 302609309 by LessNux on Monday 19th of March 2012 04:11:10 PM
Old 03-19-2012
If I need to use (or reuse) the search result later but not immediately following "find", I would like to save it into a variable. However, the search result contains null characters as separators, and bash removes null characters either upon variable assignment or upon variable expansion. To preserve null characters, the percent-encoding is useful.

Percent encoding is widely used for URL encoding. The following method applies percent-encoding to only the null character and the percent symbol itself.

Code:
#!/bin/bash
#percent-encoding for null character
PercentizeNull()
{
  sed "s/%/%25/g" | sed "s/\x0/%00/g"
}
DepercentizeNull()
{
  sed "s/%00/\x0/g" | sed "s/%25/%/g"
}
echo -ne "A\0B\0%\0" | hexdump -C
foo=$(echo -ne "A\0B\0%\0" | PercentizeNull)
printf %s "$foo" | DepercentizeNull | hexdump -C



The following example saves the search result of "find" into a variable with percent-encoding.

Code:
PercentizeNull()
{
  sed "s/%/%25/g" | sed "s/\x0/%00/g"
}
DepercentizeNull()
{
  sed "s/%00/\x0/g" | sed "s/%25/%/g"
}

vFound=$(find . -perm /o+rwx ! -type l -print0 2> /dev/null | PercentizeNull)

if test "$vFound" ; then
  echo "current permission"
  printf %s "$vFound" | DepercentizeNull | xargs -0 ls -ld
  printf %s "$vFound" | DepercentizeNull | xargs -0 chmod o-rwx
  echo "new permission"
  printf %s "$vFound" | DepercentizeNull | xargs -0 ls -ld
fi



By the way, does anyone know at which time bash removes null characters, at the time of variable assignment or at the time of variable expansion? Which time? Does bash never save null characters into a variable? Or, does bash save null characters into the variable, and does bash remove null characters when the variable is expanded?

Furthermore, without any encoding (such as percent encoding), is there any option to prevent bash from removing null characters?
Last edited by LessNux; 03-19-2012 at 05:28 PM..
 

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LEARN ABOUT CENTOS

openvt

OPENVT(1)							     Linux 1.x								 OPENVT(1)

NAME

       openvt - start a program on a new virtual terminal (VT).

SYNOPSIS

       openvt [-c vtnumber] [OPTIONS] [--] command

DESCRIPTION

       openvt  will  find the first available VT, and run on it the given command with the given command options, standard input, output and error
       are directed to that terminal. The current search path ($PATH) is used to find the requested command. If no command is specified  then  the
       environment variable $SHELL is used.

   OPTIONS
       -c, --console=VTNUMBER
	      Use the given VT number and not the first available. Note you must have write access to the supplied VT for this to work;

       -f, --force
	      Force opening a VT without checking whether it is already in use;

       -e, --exec
	      Directly execute the given command, without forking.  This option is meant for use in /etc/inittab;

       -s, --switch
	      Switch to the new VT when starting the command. The VT of the new command will be made the new current VT;

       -u, --user
	      Figure out the owner of the current VT, and run login as that user.  Suitable to be called by init. Shouldn't be used with -c or -l;

       -l, --login
	      Make the command a login shell. A - is prepended to the name of the command to be executed;

       -v, --verbose
	      Be a bit more verbose;

       -w, --wait
	      wait  for command to complete. If -w and -s are used together then openvt will switch back to the controlling terminal when the com-
	      mand completes;

       -V, --version
	      print program version and exit;

       -h, --help
	      show this text and exit.

       --     end of options to openvt.

NOTE

       If openvt is compiled with a getopt_long() and you wish to set options to the command to be run, then you must supply the end of options --
       flag before the command.

EXAMPLES

       openvt can be used to start a shell on the next free VT, by using the command:

       openvt bash

       To start the shell as a login shell, use:

       openvt -l bash

       To get a long listing you must supply the -- separator:

       openvt -- ls -l

HISTORY

       Earlier, openvt was called open.  It was written by Jon Tombs <jon@gtex02.us.es or jon@robots.ox.ac.uk>.  The -w idea is from "sam".

SEE ALSO

       chvt(1), doshell(8), login(1)

19 Jul 1996							       V1.4								 OPENVT(1)
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