BackgroundProcess

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

CommandName=${0##*/}
CommandOptionString="-c"
RunInBackgroundOptionString="-b"
KillProcessOptionString="-k"
ProcessFinishedOptionString="-f"
TempDir="/tmp"
KillProcessTimeout="1" # Max time for killed process's parent to save child process' info. '$CommandName -k ' fails if parent still running after timeout.
KillSignal=HUP

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

Usage()
{
echoE "'$CommandName' can be used to launch/control a process running in background."
echoE "Usage: '$CommandName $CommandOptionString Command [Param [Param...]]'."
echoE "\tLaunches 'Command [Param [Param...]]' in background."
echoE "\tOutputs background process Id. Exitcode 0 if successful."
echoE "Usage: '$CommandName ProcessPid'."
echoE "\tOutputs background process' info (See below)."
echoE "\tExitcode 0 if process is valid and no longer running (Info valid)."
echoE "\tExitcode 1 if process valid and still running (Info not valid)."
echoE "\tExitcode non 0 if not a valid process or any other problems"
echoE "\t (Info not valid)."
echoE "Usage: '$CommandName $ProcessFinishedOptionString ProcessPid'."
echoE "\tChecks if process with 'ProcessPid' Pid has finished running."
echoE "\tExitcode 0 if process is valid and no longer running"
echoE "\tExitcode 1 if process valid and still running."
echoE "\tExitcode non 0 if not a valid process or any other problems."
echoE "\tDoes not output any info."
echoE "Usage: '$CommandName $KillProcessOptionString ProcessPid'."
echoE "\tKills process with 'ProcessPid' Pid (Previously"
echoE "\t launched by '$CommandName')."
echoE "\tOutputs background process' info (See below)."
echoE "\tExitcode 0 if valid process and killed successfully"
echoE "\t (Or had exited already) and info read successfully."
echoE "Background process' info:"
echoE "\tText that when sourced (with 'eval') gives values to following"
echoE "\tvariables:"
echoE "\t 'CommandLine': Command and parameters of process when launched."
echoE "\t 'ElapsedTime': Time (in seconds) the process was running."
echoE "\t 'ExitCode': Exit code of process."
echoE "\t 'StandardOut': Output generated by process while running."
echoE "\t 'StandardError': Error output generated by process while running."
echoE "\tNote: To avoid mismatch in the number of \",',\`,´ (which would cause"
echoE "\t  'eval' to fail) each of them can be replaced by \\\" in 'StandardOut'"
echoE "\t  & 'StandardError' (Some commands output: \`Error message') by using"
echoE "\t  function 'CleanText' (See \$COMMON_BIN_DIR/BashCodeRepository)."
echoE "Note: Normal usage sequence:"
echoE "\tLaunch a process in background and get its Pid."
echoE "\tDo other tasks."
echoE "\tCheck if backgroung process has finished running"
echoE "\t using '$CommandName' and Pid."
echoE "\tRead info when backgroung process has finished."
echoE "\tSource background process' info and use Variables' contents."
echoE "\tIf background process has not finished in the allotted time"
echoE "\t kill it with '$CommandName' (And get info of killed process)."
echoE "Please read \$COMMON_BIN_DIR/BashCodeRepository for examples of usage."
echoE
return 0
}
########### Functions. END.

CommandOption=false;RunInBackgroundOption=false;KillProcessOption=false;ProcessFinishedOption=false
if [ "$1" == "$CommandOptionString" ]
  then
    CommandOption=true
    shift
  else
    if [ "$1" == "$RunInBackgroundOptionString" ]
      then
        RunInBackgroundOption=true
        shift
      else
        if [ "$1" == "$KillProcessOptionString" ]
          then
            KillProcessOption=true
            shift
          else
            if [ "$1" == "$ProcessFinishedOptionString" ]
              then
                ProcessFinishedOption=true
                shift
            fi
        fi
    fi
fi

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

if $CommandOption
  then
    if ! type "$1" &>/dev/null
      then
        echoE "$CommandName: Command '$1' not in \$PATH. Aborting!"
        exit 127
    fi
#   'coproc': Equivalent to ending command with '&'. '&' does not work if shell invoked with `` (ProcessId=`BackgroundProcess -c Command`)
#   &>/dev/null so that no error message is given when killed. Also to allow background processes to be launched from this background process (pipes?)
    if coproc $CommandName $RunInBackgroundOptionString "$@" &>/dev/null
      then
        eval "exec ${COPROC[0]}>&-" #Close coproc stdout pipe (See Books/Science/Computer_Science/Linux/Bash_scripting/Bash_Co_Processes)
        eval "exec ${COPROC[1]}<&-" #Close coproc stdin pipe (See Books/Science/Computer_Science/Linux/Bash_scripting/Bash_Co_Processes)
        echo "$!"
        exit 0
      else
        echoE "$CommandName: Launching in background with 'coproc' failed with ExitCode: $?. Aborting!" # Should never happen but... just in case ;-)
        exit 70
    fi
fi

if $RunInBackgroundOption
  then
    TempFile="${TempDir}/${CommandName}_$$"
    TempErrorFile="${TempFile}.Error"
    >$TempErrorFile			# So that other users can not read file
    chmod 600 $TempErrorFile		# So that other users can not read file
    TempOutFile="${TempFile}.Out"
    >$TempOutFile			# So that other users can not read file
    chmod 600 $TempOutFile		# So that other users can not read file
    cd $TempDir # So that child process uses it as working directory (And does not tie up current wd).
    exec 0<&- # Close stdin
    exec 1>&- # Close stdout
    exec 2>&- # Close stderr
    StartTime=`date +%s` # Seconds since 1970−01−01
    1>$TempOutFile 2>$TempErrorFile "$@"
    ExitCode=$?
    let ElapsedTime=`date +%s`-$StartTime
    echo -e "CommandLine=\"$@\"\n#\nElapsedTime=${ElapsedTime}\n#\nExitCode=${ExitCode}\n#\nStandardOut=\"`cat $TempOutFile`\"\n#\nStandardError=\"`cat $TempErrorFile`\"\n#" >$TempFile
    rm -f $TempErrorFile $TempOutFile
    exit 0
fi

if [ $# -ne 1 ]
  then
    Usage
    exit 64
fi

TempFile="${TempDir}/${CommandName}_$1"

if ProcessCommandName=`2>/dev/null ps --pid=$1 h -o comm`
  then
#   If $CommandName contains $ProcessCommandName (ps returns only the 15 first characters of command).
    if [ "$CommandName" != "${CommandName/${ProcessCommandName}/}" ]
      then
        if $KillProcessOption
          then
            for Grandchild in `ps -o pid --no-headers --ppid $1`
              do
                pkill -${KillSignal} -P $Grandchild &>/dev/null # Kill BackgroundProcess' children's children (grandchildren)
              done
            pkill -${KillSignal} -P $1 &>/dev/null # -P means kill processes whose parent process ID is listed. Here: kill BackgroundProcess' children
            let "KillProcessTimeout = $KillProcessTimeout * 10" # Will be checked at 1/10 seconds
            while &>/dev/null ps --pid=$1 && [ $KillProcessTimeout -gt 0 ]
              do
                sleep 0.1
              done
            if ! &>/dev/null ps --pid=$1
              then
                if [ -f $TempFile ]
                  then
                    cat $TempFile
                    rm -f $TempFile
                    exit 0
                  else
                    echoE "$CommandName: Process killed but temporary file not found. No record of process '$1'."
                    exit 70
                fi
              else
                echoE "$CommandName: Warning! Process '$1' could not be killed."
                exit 70
            fi
        fi
        echoE "$CommandName: Process '$1' still running."
        exit 1
      else
        echoE "$CommandName: Process '$1' running but not an instance of '$CommandName'. Aborting."
        exit 70
    fi
fi

if [ -f $TempFile ]
  then
    if $ProcessFinishedOption
      then
        exit 0
    fi
    if $KillProcessOption
      then
        echoE "$CommandName: Process '$1' has already exited. Kill request ignored."
    fi
    cat $TempFile
    rm -f $TempFile
  else
    echoE "$CommandName: Process not running and temporary file not found. No record of process '$1'."
    exit 70
fi