#!/bin/sh
#############################################################################
#
# Licensed Materials - Property of IBM
#
# (C) COPYRIGHT International Business Machines Corp. 2011
#
# All Rights Reserved.
#
# US Government Users Restricted Rights - Use, duplication or
# disclosure restricted by GSA ADP Schedule Contract with IBM Corp.
#
#############################################################################

#
# NAME: db2fupdt
#
# FUNCTION: db2fupdt - Update parameter=value style file
#
# USAGE: db2fupdt [-h|-?] [-d] 
#                 -f FileName -p Parameter 
#                 [-v Value] [-s Section]
#                 [-q]
#
#          -h|-?       display the usage information.
#          -d          turn debug mode on.
#          FileName    file to modify
#          Parameter   Parameter to modify (lhs of equal sign)
#          Value       New value to assign (if missing, will print to
#                      stdout the old value)
#          Section     Section to look for the parameter in, if the file
#                      has sections delimited as [Section].  If the file
#                      has no sections, -s parameter is not required.
#          -q          Quiet: no output.  Meaningless if -v is also
#                      specified (-v has no output).
#
# RETURN CODES:
#
#          If -v is specified:
#             0        Success
#             non-zero Error updating file
#
#          If -v is not specified:
#             0        Parameter found (in given section)
#             non-zero Parameter not found (in given section)
#          -q has no effect on return code
#
########################################################################

# Options for "set" command
setopts="${setopts:-+x}"
set ${setopts?}

TMPFILE="/tmp/db2fupdt.tmp.$$"    # Temporary file

syntax()
{
  echo "Not documented. (See script source)"
  exit 1
}

defaultopts()
{
  DEBUG=1
  VALUESET=1
  SECTIONSET=1
  QUIET=1
  setopts="+x"
}

#--------------------------------------------------------------------
#                    Main Program
#--------------------------------------------------------------------

defaultopts

# Process command-line options
case $# in
  0)
    syntax 
    ;;
  *)
    while getopts :dqf:p:v:s: optchar
    do
      case ${optchar?} in
        d)
          DEBUG=0
          setopts="-x"
          ;;
        f)
          FILE="${OPTARG?}"
          ;;
        p)
          PARAMETER="${OPTARG?}"
          ;;
        v)
          VALUE="${OPTARG?}"
          VALUESET=0
          ;;
        s)
          SECTION="${OPTARG?}"
          SECTIONSET=0
          ;;
        q)
          QUIET=0
          ;;
        *) # h or ?(error)
          syntax
          ;;
      esac
    done
    ;;
esac

# Both the -f and -p must be set.
if [ "X${FILE}" = "X" -o "X${PARAMETER}" = "X" ]
then
  syntax
fi

# if the file doesn't exist...
if [ ! -f ${FILE?} ]
then
  # and we're setting a value, touch it (create it)
  if [ ${VALUESET?} -eq 0 ]
  then
    touch ${FILE?}
  else
  # otherwise, return immediately (the value is not set, and no output)
    exit 1
  fi
fi

set ${setopts?}

# AWK variables:
#   found -> has the parameter been found?
#   section -> are we in the right section?
#              If -s wasn't specified, we're always in the right section.
#   sectionfound -> was the section found?

# always start as not foudn.
AWKSCRIPT="BEGIN{ found=0;"
if [ ${SECTIONSET?} -eq 0 ]
then
  # looking for a section.
  # A section looks like [.*].
  # if this is a section, find out if it's the *right* section.  If so,
  # save this fact.
  AWKSCRIPT="${AWKSCRIPT?} section=0; sectionfound=0; }
/^\[.*\]/{
  if (\$1 == \"[${SECTION?}]\") {
    section = 1;
    sectionfound = 1;
  } else {
"
  # if there is a value to set, and we're leaving the right section,
  # put the parameter and value into the section now before we leave it.
  if [ ${VALUESET?} -eq 0 ]
  then
    AWKSCRIPT="${AWKSCRIPT?} 
    if ( found == 0 && section == 1 ) {
      print \"${PARAMETER?}=${VALUE?}\"
    }"
  fi

  # since this was not the right section, set that we've left it.
    AWKSCRIPT="${AWKSCRIPT?}
    section = 0;
  }
}"
else
  # if no section specified, we're always in the right section.
  AWKSCRIPT="${AWKSCRIPT?} section=1; sectionfound=1; }"
fi

# if we've found the parameter, which is left-aligned, ending with an equals
# sign, check if we're in the right section.
AWKSCRIPT="${AWKSCRIPT?}
/^${PARAMETER?}=/{ 
  if ( section == 1 ) {"
if [ ${VALUESET?} -eq 0 ]
then
  # If we're to reset the value, change it here.
  AWKSCRIPT="${AWKSCRIPT?}
    sub(\"=.*\$\",\"=${VALUE?}\"); "
else
  # Otherwise, remove the front, and print it out.
  AWKSCRIPT="${AWKSCRIPT?}
    sub(\"^.*=\",\"\"); 
    print \$0;"
fi
# However, either way, we found what we're looking for.
AWKSCRIPT="${AWKSCRIPT?} 
    found = 1 
  }
}"

if [ ${VALUESET?} -eq 0 ]
then
  # if we're changing the value, we need to print out every line so we
  # can put it back in the original file.
  AWKSCRIPT="${AWKSCRIPT?}
{ print \$0 }"
fi

if [ ${VALUESET?} -eq 0 ]
then
  # If we're changing a value, the parameter may not actually exist.
  # We'll have to create it.
  AWKSCRIPT="${AWKSCRIPT?}
END{"

  # If the section didn't even exist, we have to create the section, too.
  if [ ${SECTIONSET?} -eq 0 ]
  then
    AWKSCRIPT="${AWKSCRIPT?}
  if ( sectionfound == 0 ) {
    print \"[${SECTION?}]\""
  else
    AWKSCRIPT="${AWKSCRIPT?}
  if ( found == 0 ) {"
  fi

  AWKSCRIPT="${AWKSCRIPT?}
    print \"${PARAMETER?}=${VALUE?}\"
  }
}
"
fi

rm -f ${TMPFILE?}
awk "${AWKSCRIPT?}" ${FILE?} > ${TMPFILE?}

if [ ${VALUESET?} -ne 0 ]
then
  # if we merely are returning the value, display it.
  if [ ${QUIET?} -ne 0 ]
  then
    cat ${TMPFILE?}
  fi

  # return value is true if we found a value, false otherwise.
  LINES=`wc -l < ${TMPFILE?}`
  exitcode=1
  if [ ${LINES?} -ne 0 ]
  then
    exitcode=0
  fi
else
  # Otherwise, place it back over the original file.

  # make sure we keep its owner/group settings!
  cat /dev/null > ${FILE?} && cat ${TMPFILE?} >> ${FILE?}
  exitcode=$?
fi
# error or not, clean up temp file
rm -f ${TMPFILE?} > /dev/null 2>&1

exit ${exitcode?}