#!/bin/ksh
# @(#) filt.ksh 2.0 96/11/09
# 92/10/08 john h. dubois iii (john@armory.com)
# 96/11/09 Added all options.

# Use ksh because sh "type" doesn't exit nonzero if it fails
# & ksh has continue <n>

name=${0##*/}
Usage="Usage: $name [-efhcnv] [-f<file>] <filter> [<file> ...]"
overwrite=false
backup=true
check=true
eval=
filesGiven=false
verbose=false

while getopts eohcnf:v opt; do
    case $opt in
    h)
	print -r -- \
"$name: filter files.
Each <file> is passed to <filter> as its standard input.
Output is written to <file>+.  If the exit value of <filter> is zero,
the original file is moved <file>- and the output is moved to <file>.
$Usage
Options:
-h: Print this help.
-v: Be verbose.
-e: \"eval\" the filter command.  This is neccessary if it contains
    characters that must be interpreted by the shell, like quoting characters.
    Example: $name -e \"grep 'foo bar'\" file
-f<file>: Specify a file to be filtered.  If a filename is given with -f, the
    remaining (non-option) arguments are all taken to be part of the filter
    command.  This is an alternative to the -e option for specifying complex
    filter commands.  Multiple -f arguments may be given.
-o: Normally $name will skip a file if <file>+ or (if -n is not given) <file>-
    already exists.  If -f is given, they will be overwritten.
-c: After a successful filter, instead of moving files, copy them: <file>
    is copied to <file>-, <file> is overwritten with the contents of <file>+,
    and then <file>+ is removed.  This preserves the original inode of <file>.
-n: Do not keep a backup copy of <file> in <file>-."
	exit 0
	;;
    f)
	set -A files -- "${files[@]}" "$OPTARG"
	filesGiven=true
	;;
    e)
	eval=eval
	;;
    c)
	overwrite=true
	;;
    o)
	check=false
	;;
    n)
	backup=false
	;;
    v)
	verbose=true
	;;
    ?)
	print -r -u2 "Use -h for help."
	exit 1
	;;
    esac
done

# remove args that were options
let OPTIND=OPTIND-1
shift $OPTIND

if [ $# -lt 2 ]; then
    print -r -u2 -- "$Usage
Use -h for help."
    exit 1
fi

if $filesGiven; then
    set -A filter -- "$@"
else
    tm=$1
    shift
    set -A files -- "$@"	# some ksh lose positional param when -A used
    set -A filter -- $tm
fi

type "${filter[0]}" >/dev/null 2>&1 || {
    print -ru2 -- "Cannot execute filter command: ${filter[0]}"
    exit 1
}

for file in "${files[@]}"; do
    if $check; then
	if [ -f "$filt+" ]; then
	    print -ru2 -- "$filt+ already exists.  $file not processed."
	    continue
	fi
	if $backup && [ -f "$file-" ]; then
	    print -ru2 -- "$file- already exists.  $file not processed."
	    continue
	fi
    fi
    if [ ! -r "$file" ]; then
	print -ru2 -- "$file: cannot read."
	continue
    fi
    $verbose && print -r -- "Filtering $file..."
    if $eval "${filter[@]}" < "$file" > "$file+"; then
	if $backup; then
	    $verbose && print -r -- "Backing up $file..."
	    $overwrite && cp -- "$file" "$file-" || mv -- "$file" "$file-"
	    if [ $? -ne 0 ]; then
		print -ru2 -- \
	    "Backup of $file to $file- failed; filtered contents left in $file+"
		exit 1
	    fi
	fi
	if $verbose; then
	    print -r -- "Old file:"
	    l -- "$file"
	    print -r -- "After filtering:"
	    l -- "$file+"
	    print -r -- "Replacing contents of $file with filtered contents..."
	fi
	$overwrite && cat -- "$file+" > "$file" || mv -- "$file+" "$file"
	if [ $? -ne 0 ]; then
	    print -ru2 -- \
"Move of filtered contents to $file back to $file failed;
contents of $file may be inconsistent!!"
	    exit 1
	fi
	if $overwrite; then
	    $verbose && print -r -- "Removing $file+..."
	    rm -- "$file+"
	fi
	print -r -- "$file succesfully filtered."
    else
	print -r -- "filter exited nonzero on file $file; $file not touched."
    fi
done