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#!/bin/sh
set -eu
usage() {
cat <<-'EOF'
Usage:
ifnew FILE
ifnew -h
EOF
}
help() {
cat <<-'EOF'
Options:
-h, --help show this message
FILE the target to compared against
Compare STDIN to FILE, and only write to FILE if STDIN content
differs from FILE content.
Examples:
Create a new file, don't update it afterwards, and update it
as the content changes:
$ echo aaa | ifnew new-file
$ stat --print='%y' new-file
# timestamp 1
$ echo aaa | ifnew new-file
$ stat --print='%y' new-file
# timestamp 1
$ echo bbb | ifnew new-file
$ stat --print='%y' new-file
# timestamp 2
Only change file when content changes in a Makefile:
i18.cfg: ALWAYS
gen-cfg | ifnew $@
po4a $@
EOF
}
for flag in "$@"; do
case "$flag" in
--)
break
;;
--help)
usage
help
exit
;;
*)
;;
esac
done
while getopts 'h' flag; do
case "$flag" in
h)
usage
help
exit
;;
*)
usage >&2
exit 2
;;
esac
done
shift $((OPTIND - 1))
FILE="${1:-}"
eval "$(assert-arg -- "$FILE" 'FILE')"
STDIN="$(mkstemp)"
trap 'rm -f "$STDIN"' EXIT
cat - > "$STDIN"
if ! cmp -s "$STDIN" "$FILE"; then
mv "$STDIN" "$FILE"
fi
|
