partextend

partextend

#!/bin/bash
set -e
set -o pipefail

partdev=${1:?}

partdev=$(readlink -f -- "$partdev")  
echo "Canonical partition: ${partdev}"

if false; then
  
  # TODO: lvm/
  sysdev=$(readlink -- "/sys/class/block/${partdev##*/}")
  sysdev=${sysdev%/*}
  sysdev=${sysdev##*/}
  
  dev=/dev/$sysdev
else
  if ! dev=/dev/$(lsblk -no pkname -- "$partdev"); then
    dev=${partdev%?}
  fi
fi

echo "Parent device: $dev"
echo

LF='
'

LC_ALL=C

follower_start=`blockdev --getsize "$dev"` || {
  # image file?
  follower_start=$(stat -c%s test.img)
  follower_start=$((follower_start / 512))
}

exec 3<&0

sfdisk -d "$dev" | tac | {

    newdump=
    newsize=

    echo "### current table (in reverse order): ###"

    body=x

    while IFS= && read -r line; do
        printf '%s\n' "$line"
        if [ -z "$line" ]; then
          # end of partitions
          body=
        fi

        if [ "$body" ]; then
          IFS=':,'
          start=unknown
          size=unknown
          linedev=
          for nameval in $line; do
              if [ -z "$linedev" ]; then
                IFS=' '
                for linedev in $nameval; do : ; done
                continue # for nameval in $line
              fi
              IFS=' ='
              varname=
              for nameorval in $nameval; do
                  if [ "$varname" ]; then
                      eval "$varname=\$nameorval"
                  else
                      case $nameorval in
                      'size'|'start')
                          varname=$nameorval
                          ;;
                      *)
                          break
                          ;;
                      esac
                  fi
              done
          done
  
          if [ x"$linedev" = x"$partdev" ]; then
            newsize=$((follower_start - start))
            if [ $newsize -eq $size ]; then
              newsize=
            else
              suf=${line#*size=}
              suf=${suf#*,}
              pref=${line%size=*}
              line="${pref}size=${newsize},${suf}"
            fi
          fi
          follower_start=$start
        fi # body

        newdump=${line}${LF}${newdump}
    done # read -r line

    echo

    if [ -z "$newsize" ]; then
      echo "Nothing to do"
      exit
    fi

    exec 0<&3

    echo ""
    echo ""
    echo "### new table: ###"

    echo "cat <<'EOF' | sfdisk $SFDISK_FLAGS '$dev'"
    printf '%s' "$newdump"
    echo EOF

    while read -p "is this ok? [yes,no] " s; do
        if [ "no" = "$s" ]; then
            exit
        fi
        if [ "yes" = "$s" ]; then
            printf '%s' "$newdump" | sfdisk $SFDISK_FLAGS "$dev" || {
              >&2 echo "sfdisk failed. Set SFDISK_FLAGS env. var. and retry this script"
              exit 1
            }
            break
        fi
    done
}