RunInNewHOME

#!/bin/bash
#Written by Manuel Iglesias. glesialo@gmail.com

CommandName=${0##*/}
ReferenceDirOption="-r"
TempDir=/tmp
ServiceAvailableOptionStr="-sa" # Same value for all 'Application Service' scripts (Check $COMMON_BIN_DIR/DefaultApplications).
ApplicationServiceCommands="DefaultBrowser DefaultBrowser2 DefaultBrowser3" # Commands that exit immediately. $Command makes a request to an already running binary.
IntervalWaitingForApplicationServices=10 # Seconds
HomePlaceHolder=HOMEVALUE
#Xdg dirs: special directories where applications leave config, cache, etc files
#Environment variables: XDG_CACHE_HOME=$HOME/.cache; XDG_CONFIG_HOME=$HOME/.config; XDG_DATA_HOME=$HOME/.local/share
XdgEnvVars="XDG_CACHE_HOME=${HomePlaceHolder}/.cache XDG_CONFIG_HOME=${HomePlaceHolder}/.config XDG_DATA_HOME=${HomePlaceHolder}/.local/share"
SpecialNotDotItemsToLink="Desktop Documents Downloads Music Pictures Public Templates Videos var" # Space separated.
#To override configuration dirs/files create directories/files as needed:
#  NewHOME/Application (or Application.cfg)
#To override Xdg directories, create directories as needed:
#  NewHOME/.cache/ApplicationDir
#  NewHOME/.config/ApplicationDir
#  NewHOME/.local/share/ApplicationDir



echoE()
{
echo -e "#$*" 1>&2
return 0
}

Usage()
{
echoE "'$CommandName' changes, temporarily, HOME variable to 'NewHomeDir'"
echoE "and then runs the specified Command with the supplied Arguments."
echoE "'$CommandName' creates links to \$HOME directories and files in:"
echoE "\t'NewHomeDir'"
for SubDir in $XdgDirs
  do
    echoE "\t'NewHomeDir/${SubDir}'"
  done
echoE "Notes:"
echoE "\tAbove links will be removed when Command exits."
echoE "\t'NewHomeDir' must exist."
echoE "\t'NewHomeDir's contents can be updated to those of a"
echoE "\t  reference directory if '$ReferenceDirOption' option is used."
echoE "\tOnly one instance of '$CommandName' can be run for a"
echoE "\t  given, 'NewHomeDir', directory."
echoE
echoE "Usage: '$CommandName NewHomeDir Command [CommandArguments]'."
echoE "or"
echoE "Usage: '$CommandName $ReferenceDirOption ReferenceDir NewHomeDir Command [CommandArguments]'."
echoE
return 0
}



XdgDirs=""
for Item in $XdgEnvVars
  do
    XdgDirs="${Item##*${HomePlaceHolder}/} ${XdgDirs}"
  done # XdgDirs contains ".local/share .config .cache"

ReferenceDir="";ReferenceDirOptionUsed=false
if [ "$1" == "$ReferenceDirOption" ]
  then
    ReferenceDirOptionUsed=true
    if [ $# -gt 1 ]
      then
        ReferenceDir="$2"
        shift; shift # '$ReferenceDirOption Dir' parameters removed. Dir in $ReferenceDir.
      else
        echoE "$CommandName: Warning! A directory should follow '$ReferenceDirOption'."
        echoE
        Usage
        exit 64
    fi
    if [ ! -d "$ReferenceDir" ]
      then
        echoE "$CommandName: '$ReferenceDir' is not a valid directory"
        exit 70
    fi
fi
# Now $@ contains "NewHomeDir Command [CommandArguments]"

if [ $# -lt 2 ] || [ "$1" == "-h" ] || [ "$1" == "-?" ] || [ "$1" == "--help" ] || [ "$1" == "-help" ]
  then
   Usage
   exit 64
fi

if [ ! -d "$1" ]
  then
    echoE "$CommandName: '$1' is not a valid directory"
    exit 70
fi

CommandLines="$(ps -C "$CommandName"  h -o pid,command)" # No headers, print pid and commandline.
while read CommandLine
  do
    if [ "${CommandLine%% *}" != "$$" ] # Skip this process commandline.
      then
        if [ "$CommandLine" != "${CommandLine/${0}/}" ] && [ "$CommandLine" != "${CommandLine/${1}/}" ]
          then # CommandLine contains $0 AND $1 (Full path command and NewHomeDir).
            echoE "$CommandName: Instance of '$CommandName' already running for the given directory. Aborting."
            exit 69
        fi
    fi
  done <<<"$CommandLines"

OldHome="$HOME"
HOME="$(cd "$1";pwd)" # Expands relative paths

if $ReferenceDirOptionUsed
  then
    cd "$ReferenceDir"
    if ! cp --force --recursive --update --target-directory="$HOME" . &>/dev/null
      then
        echoE "$CommandName: Updating from '${ReferenceDir}' failed. Aborting."
        exit 70
      else
        echo "$CommandName: '$HOME' updated from '${ReferenceDir}'."
    fi
fi

Command=$2; shift; shift # $@ contains CommandArguments (if any)

if ! type "$Command" &>/dev/null # Check if command available
  then
    echoE "$CommandName: Command '$Command' not available."
    exit 127
fi

if ! TempDir=$(mktemp -dq $TempDir/$CommandName.XXXXXX) &>/dev/null
  then
    echoE "$CommandName: Can't create temporary directory. Aborting."
    exit 73
fi

ItemsToLink="${OldHome}/.*"
for Item in $SpecialNotDotItemsToLink
  do
     ItemsToLink="${OldHome}/${Item} $ItemsToLink"
  done
for Item in $ItemsToLink
  do
    if [ -e "$Item" ] && [ "${Item##*/}" != "." ] && [ "${Item##*/}" != ".." ]
      then
        ln -s "$Item" "$TempDir" &>/dev/null
    fi
  done

for Item in "$TempDir"/* "$TempDir"/.*
  do
    if [ -e "$Item" ] && [ "${Item##*/}" != "." ] && [ "${Item##*/}" != ".." ]
      then
        if [ ! -e "$HOME/${Item##*/}" ]
          then
            if [ -h "$HOME/${Item##*/}" ] # If "$HOME/${Item##*/}" is a (broken: doesn't exist: see above) link
              then
                if ! rm "$HOME/${Item##*/}" &>/dev/null
                  then
                    echoE "$CommandName: Warning: Failed to remove broken link '$HOME/${Item##*/}'."
                fi
            fi
            if ! ln -s "$Item" "$HOME" &>/dev/null
              then
                echoE "$CommandName: Warning: Failed to create link '$HOME/${Item##*/}'."
            fi
        fi
    fi
  done

for Item in $XdgDirs
  do
    if [ -e "${HOME}/$Item" ] && [ ! -L "${HOME}/$Item" ] # If Item exists in $HOME (NewHomeDir) and it is not a symbolic link
      then
        for SubItem in "$TempDir/$Item"/* "$TempDir/$Item"/.*
          do
            if [ -e "$SubItem" ] && [ "${SubItem##*/}" != "." ] && [ "${SubItem##*/}" != ".." ]
              then
                if [ ! -e "$HOME/$Item/${SubItem##*/}" ]
                  then
                    if [ -h "$HOME/$Item/${SubItem##*/}" ] # If "$HOME/$Item/${SubItem##*/}" is a (broken: doesn't exist: see above) link
                      then
                        if ! rm "$HOME/$Item/${SubItem##*/}" &>/dev/null
                          then
                            echoE "$CommandName: Warning: Failed to remove broken link '$HOME/$Item/${SubItem##*/}'."
                        fi
                    fi
                    if ! ln -s "$SubItem" "$HOME/$Item" &>/dev/null
                      then
                        echoE "$CommandName: Warning: Failed to create link '$HOME/$Item/${SubItem##*/}'."
                    fi
                fi
            fi
          done
    fi
  done

cd "$HOME"
export HOME
export HOME_VAR_DIR="${HOME}/var" # In case there is a local var folder
for Item in $XdgEnvVars #Export: XDG_CACHE_HOME=$HOME/.cache; XDG_CONFIG_HOME=$HOME/.config; XDG_DATA_HOME=$HOME/.local/share
  do
    export ${Item//${HomePlaceHolder}/$HOME}
  done

$Command "$@"
ExitCode=$?

######################
#Special case for 'Application Service' Commands that exit immediately. $Command makes a request to an already running binary.
Temp="$ApplicationServiceCommands";ApplicationServiceCommands=""
for SpecialCommand in $Temp
  do
    ApplicationServiceCommands="${ApplicationServiceCommands}_${SpecialCommand}_" # _$SpecialCommand_ to tell apart names with same base (DefaultBrowser, DefaultBrowser2).
  done
if [ "$ApplicationServiceCommands" != "${ApplicationServiceCommands/_${Command}_/}" ] #If $Command is in $ApplicationServiceCommands
  then
    if Pid=$($Command $ServiceAvailableOptionStr) # Pid of runnig binary
      then # Keep this shell instance running until $Command binary exits.
        while ps --pid=$Pid &>/dev/null
          do
            sleep $IntervalWaitingForApplicationServices
          done
    fi
fi
######################

if ! rm -R "$TempDir" &>/dev/null
 then
   echoE "$CommandName: Warning: '$TempDir' could not be removed."
fi

for Item in "$HOME"/* "$HOME"/.*
  do
    if [ -h "$Item" ] && [ ! -e "$Item" ] # If Item is a broken link
      then
        if ! rm "$Item" &>/dev/null
          then
            echoE "$CommandName: Warning: Failed to remove broken link '$Item'."
        fi
    fi
  done

for Item in $XdgDirs
  do
    if [ -e "$HOME/$Item" ] && [ ! -L "$HOME/$Item" ] # If Item exists in $HOME (NewHomeDir) and it is not a symbolic link
      then
        for SubItem in "$HOME/$Item"/* "$HOME/$Item"/.*
          do
            if [ -h "$SubItem" ] && [ ! -e "$SubItem" ] # If SubItem is a broken link
              then
                if ! rm "$SubItem" &>/dev/null
                  then
                  echoE "$CommandName: Warning: Failed to remove broken link '$SubItem'."
                fi
            fi
          done
    fi
  done

exit $ExitCode