Mini Shell

#!/usr/bin/bash

#   Copyright (C) 2003-2018 Free Software Foundation, Inc.

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

#
# Script to generate a core file of a running program.
# It starts up gdb, attaches to the given PID and invokes the gcore command.
#

# Need to check for -o option, but set default basename to "core".
name=core

# When the -a option is present, this may hold additional commands
# to ensure gdb dumps all mappings (OS dependent).
dump_all_cmds=()

while getopts :ao: opt; do
    case "$opt" in
        a)
            case "$OSTYPE" in
                linux*)
                    dump_all_cmds=("-ex" "set use-coredump-filter off")
                    dump_all_cmds+=("-ex" "set dump-excluded-mappings on")
                    ;;
            esac
            ;;
        o)
            name=$OPTARG
            ;;
        *)
            echo "usage:  gcore [-a] [-o filename] pid"
            exit 2
            ;;
    esac
done

shift $((OPTIND-1))

if [ "$#" -eq "0" ]
then
    echo "usage:  gcore [-a] [-o filename] pid"
    exit 2
fi

# Attempt to fetch the absolute path to the gcore script that was
# called.
binary_path=`dirname "$0"`

if test "x$binary_path" = x. ; then
  # We got "." back as a path.  This means the user executed
  # the gcore script locally (i.e. ./gcore) or called the
  # script via a shell interpreter (i.e. sh gcore).
  binary_basename=`basename "$0"`

  # If the gcore script was called like "sh gcore" and the script
  # lives in the current directory, "which" will not give us "gcore".
  # So first we check if the script is in the current directory
  # before using the output of "which".
  if test -f "$binary_basename" ; then
    # We have a local gcore script in ".".  This covers the case of
    # doing "./gcore" or "sh gcore".
    binary_path="."
  else
    # The gcore script was not found in ".", which means the script
    # was called from somewhere else in $PATH by "sh gcore".
    # Extract the correct path now.
    binary_path_from_env=`which "$0"`
    binary_path=`dirname "$binary_path_from_env"`
  fi
fi

# Check if the GDB binary is in the expected path.  If not, just
# quit with a message.
if [ ! -f "$binary_path/gdb" ]; then
  echo "gcore: GDB binary (${binary_path}/gdb) not found"
  exit 1
fi

# Initialise return code.
rc=0

# Loop through pids
for pid in "$@"
do
	# `</dev/null' to avoid touching interactive terminal if it is
	# available but not accessible as GDB would get stopped on SIGTTIN.
	"$binary_path/gdb" </dev/null --nx --batch --readnever \
	    -ex "set pagination off" -ex "set height 0" -ex "set width 0" \
	    "${dump_all_cmds[@]}" \
	    -ex "attach $pid" -ex "gcore $name.$pid" -ex detach -ex quit

	if [ -r "$name.$pid" ] ; then
	    rc=0
	else
	    echo "gcore: failed to create $name.$pid"
	    rc=1
	    break
	fi


done

exit $rc