#!/bin/bash
#
# Timothy Brooks 2012 <brooks@cern.ch>
#
# caproc - take over the stdout and stderr of a process
#
# e.g: 
# $ ./myexec <ctrl-z>
# [1]+  Stopped                 ./myexec
# source caproc.sh
# Capturing process 1234 to /tmp/brooks/1234.std{out,err}
# 
# or:
# $ ./myexec <ctrl-z>
# [1]+  Stopped                 ./myexec
# $ jobs -l
# [1]+  1234 Stopped                 ./myexec\
# $ caproc -d /tmp/$USER 1234
# Capturing process 1234 to /tmp/brooks/1234.std{out,err}
# $ bg 1 && disown -h 1
# $ <ctrl-d>
# Connection closed.
#
VERSION=1.0                                    # first finished tested version
VERSION=1.1                                    # added preliminary -t TERM support
VERSION=1.2                                    # preserve $TERM
VERSION=1.3                                    # add redirection to a file (and /dev/null)

PROG="caproc"

OUTDIR=/tmp/${USER}                            # default to dropping outputs in /tmp/${USER}
unset OPTIND
unset PID
unset JOB

INTER=$(echo $- | grep i -q; echo $?)          # is this an interactive shell? (bash logic)

term () {
    TERM=$OLDTERM
}

OLDTERM=$TERM
trap term EXIT
TERM=""

while getopts "vhnf:d:j:t:" opt; do
  #echo opt: ${opt} arg: ${OPTARG}
  case $opt in
    h)
      PID="NULL"
      break ;;
    v)
      echo ${PROG} ${VERSION}
      if [ "$INTER" == 0 ]; then
        kill -SIGINT $$
      else
        exit 0
      fi ;;
    n)
      OUTFILE="/dev/null" ;;
    f)
      OUTFILE=${OPTARG} ;;
    d)
      OUTDIR=${OPTARG} ;;
    j)
      JOB=${OPTARG} ;;
    t)
      TERM=${OPTARG} ;;
    \?)
      echo "Invalid option: -${OPTARG}" >&2
      PID="NULL"
      break ;;
    :)
      echo "Option -${OPTARG} requires an argument." >&2
      PID="NULL"
      break ;;
  esac
done

if [ -z "$PID" ]; then                         # if $PID is null, then set it to the last option:
  eval PID=\$${OPTIND}
  exists=$(kill -0 ${PID} &> /dev/null; echo $?)
  if [ -n "$PID" -a "$exists" != "0" ]; then   # unless thats not a process
    echo "PID ${PID} not found"
    if [ "$INTER" == 0 ]; then
      kill -SIGINT $$
    else
      exit 1
    fi
  fi
fi

if [ -n "$PID" -a -n "$JOB" ]; then            # warn if -j and PID used together
  echo "Option -j is exclusive of PID" >&2
  PID="NULL"
elif [ -n "$JOB" ]; then                       # use JOB if -j specified
  PID=$(jobs -l | grep "^\[${JOB}\]" | awk '{print $2}')
  if [ -z "$PID" ]; then
    echo "Job ${JOB} not found"
    if [ "$INTER" == 0 ]; then
      kill -SIGINT $$
    else
      exit 1
    fi
  fi
elif [ -z "$PID" ]; then                       # if neither -j or PID specified, use the last job
  PID=$(jobs -l | tail -n1 | awk '{print $2}')
  JOB=$(jobs | tail -n1 | sed -n '/^\[\([0-9]\+\)\].*/s//\1/p')
fi

if [ -z "$PID" -o "$PID" == "NULL" ]; then     # print usage message if we still don't have PID or it's "NULL"
  echo "usage: ${PROG} [options] [PID]" >&2
  echo "" >&2
  echo "options:" >&2
  echo "  -v                    show program's version number ($VERSION) and exit" >&2
  echo "  -h                    show this help message and exit" >&2
  echo "  -n                    redirect stdout,err to /dev/null" >&2
  echo "  -f OUTFILE            path to direct stdout,err to" >&2
  echo "  -d OUTDIR             path to place output files" >&2
  echo "  -j JOB                capture and background JOB" >&2
  echo "" >&2
  echo "if no PID or job is given, but there are jobs, the last job is taken" >&2
  test 0 == 1
  if [ "$INTER" == 0 ]; then
    kill -SIGINT $$
  else
    exit 0
  fi
fi


if [ -n "$TERM" ]; then
  echo "Capturing process ${PID} to ${OUTDIR}/${PID}.std{out,err}"
  STDIN='p dup2(open("'${TERM}'",0,0))'
  STDOUT='p dup2(open("'${TERM}'",0,1))'
  STDERR='p dup2(open("'${TERM}'",0,2))'
  gdb -p "${PID}" --batch-silent -ex "p close(0)" -ex "$STDIN" \
                               -ex "p close(1)" -ex "$STDOUT" \
                               -ex "p close(2)" -ex "$STDERR"
elif [ -n "$OUTFILE" ]; then
  echo "Redirecting process ${PID} to ${OUTFILE}"
  [ -f "$OUTFILE" ] && touch "$OUTFILE"        # guarantee the output file exists
  STDOUT='p creat("'${OUTFILE}'",0600)'
  STDERR='p creat("'${OUTFILE}'",0600)'
  gdb -p "${PID}" --batch-silent -ex "p close(1)" -ex "$STDOUT" \
                               -ex "p close(2)" -ex "$STDERR"
else
  echo "Redirecting process ${PID} to ${OUTDIR}/${PID}.std{out,err}"
  mkdir -p "${OUTDIR}"                         # guarantee the output directory exists
  STDOUT='p creat("'${OUTDIR}/${PID}.stdout'",0600)'
  STDERR='p creat("'${OUTDIR}/${PID}.stderr'",0600)'
  gdb -p "${PID}" --batch-silent -ex "p close(1)" -ex "$STDOUT" \
                               -ex "p close(2)" -ex "$STDERR"
fi


if [ -n "$JOB" ]; then
  bg "$JOB"
  #echo disown -h $JOB                         # we don't seem to need this
fi