#!/bin/bash

# bestcompress--Given a file, tries compressing it with all the available
#   compression tools and keeps the compressed file that's smallest, 
#   reporting the result to the user. If -a isn't specified, bestcompress
#   skips compressed files in the input stream.

setglobal Z = '"compress',"     gz = '"gzip',"     bz = '"bzip2'"
setglobal Zout = ""/tmp/bestcompress.$Pid.Z""
setglobal gzout = ""/tmp/bestcompress.$Pid.gz""
setglobal bzout = ""/tmp/bestcompress.$Pid.bz""
setglobal skipcompressed = '1'

if test $1 = "-a"  {
  setglobal skipcompressed = '0'  ; shift
}

if test $Argc -eq 0 {
  echo "Usage: $0 [-a] file or files to optimally compress" > !2; exit 1
}

trap "/bin/rm -f $Zout $gzout $bzout" EXIT

for name in [@Argv]
{ 
  if test ! -f $name  { 
    echo "$0: file $name not found. Skipped." > !2
    continue
  }

  if test $[echo $name | egrep '(\.Z$|\.gz$|\.bz2$)] != ""  {
    if test $skipcompressed -eq 1  {
      echo "Skipped file $(name): It's already compressed." 
      continue
    } else {
      echo "Warning: Trying to double-compress $name" 
    }
  }

# Try compressing all three files in parallel.
  $Z  < $name > $Zout  &
  $gz < $name > $gzout &
  $bz < $name > $bzout &
  
  wait  # until all compressions are done

# Figure out which compressed best.
  setglobal smallest = $[ls -l $name $Zout $gzout $bzout | \
     awk '{print $5"="NR}' | sort -n | cut -d= -f2 | head -1]

  match $smallest {
     with 1  echo "No space savings by compressing $name. Left as is."
         
     with 2  echo Best compression is with compress. File renamed $(name).Z
         mv $Zout "$(name).Z" ; rm -f $name
         
     with 3  echo Best compression is with gzip. File renamed $(name).gz
         mv $gzout "$(name).gz" ; rm -f $name
         
     with 4  echo Best compression is with bzip2. File renamed $(name).bz2
         mv $bzout "$(name).bz2" ; rm -f $name
  }

}

exit 0