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Re: [PATCH] Add new option --in-place

From: Pádraig Brady
Subject: Re: [PATCH] Add new option --in-place
Date: Mon, 22 Mar 2010 10:37:20 +0000
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20100227 Thunderbird/3.0.3

On 22/03/10 03:26, Pádraig Brady wrote:
> Right. So the logic would be something like:

Here is a tested `replace` script which is backwards
compatible (non atomically) with older coreutils.


me=$(basename $0)

usage() {
  err=$1; out=2
  [ $err -eq 0 ] && out=1
  echo "$me 'filter' FILE..." >&$out
  exit $err

version() {
  Cmd=$1; Date=2010; Version=8.5 #TODO: auto update
  #TODO: translation
  printf "\
$Cmd (GNU coreutils) $Version
Copyright (C) $Date Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Pádraig Brady.
  exit 0

# TODO: perhaps support the --compare like `install`
# so as to not cp/mv if ! cmp -s -- "$tf" "$file"

if test "$#" -lt 2; then
  test "$1" = "--help" && usage 0
  test "$1" = "--version" && version $me
  usage 1

filter="$1"; shift

cleanup() { rm -f "$tf"; }
trap "cleanup" EXIT

for file in "$@"; do
  dir=$(dirname -- "$file")
  tf=$(mktemp -q --tmpdir="$dir")
  if test -e "$tf" && cp --attr -- "$file" "$tf" 2>/dev/null; then
    # Modify file atomically.
    # We could `chmod u+rw` here to allow updating non rw files?
    $filter < "$file" > "$tf" &&
    { mv -- "$tf" "$file" || fail=1; } # rename
    # cp doesn't support --attributes-only or
    # $dir is not writeable.  In this case we
    # use $TMPDIR, but don't use mv to unlink/copy
    # as $TMPDIR might not support all attrs of $dir.
    # Also we can't unlink in unwriteable dir.
    # Note we won't be able to update non rw files like this.
    $filter < "$file" > "$tf" &&
    { cp -- "$tf" "$file" || fail=1; } # truncate and copy

exit $fail

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