Gzipping without replacing original

[Aleksandersen]

This command compresses all files in a directory and it's subdirectory and replaces them by compressed files.

$ gzip --recursive --best ./*

But how to make gzip compress the files but leave the original files alone? (Not replacing.)

[scm]

find ./* -type f | while read file
do
    gzip --best <$file >$file.gz
done

[drl]

Hi.

This is on the first screen of man gzip ... cheers, drl

DESCRIPTION
Gzip reduces the size of the named files using Lempel-Ziv coding
(LZ77). Whenever possible, each file is replaced by one with the
extension .gz, while keeping the same ownership modes, access and modi-
fication times. (The default extension is -gz for VMS, z for MSDOS,
OS/2 FAT, Windows NT FAT and Atari.) If no files are specified, or if
a file name is "-", the standard input is compressed to the standard
output. (emphasis mine)

The man command (with experimentation) is one of your best friends ... cheers, drl

[Aleksandersen]

find ./* -type f | while read file
do
    gzip --best <$file >$file.gz
done

Thanks. Can I have it assume that it should overwrite existing files without using the --force option?

[scm]

Yes, in my code it's the shell that's opening and truncating the output file so gzip knows nothing about it. > will always truncate an existing file (as I've sometimes learned to my detriment when I get the input redirection character wrong!).

[Aleksandersen]

Thank you. I did not know that about ‘>’. (Even though I have seen it used many times.)

[drl]

Hi.

Yes, in my code it's the shell that's opening and truncating the output file so gzip knows nothing about it. > will always truncate an existing file (as I've sometimes learned to my detriment when I get the input redirection character wrong!).

Knowing that the shell takes care of re-direction and how it can destroy files is valuable information, and the attending lesson is one many of us re-learn from time to time

There are mechanisms in most shells to protect one's files. Here is how it works in bash:

#!/usr/bin/env bash

# @(#) s1       Demonstrate over-writing files with re-direction.

set -o nounset
echo

debug=":"
debug="echo"

## Use local command version for the commands in this demonstration.

echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version bash

# Remove debris.
rm -r t1

echo

echo " Create a file:"
echo Hello >t1
cat t1

echo
echo " Clobber the file:"
echo Goodbye >t1
cat t1

echo
echo " Set protection on:"
set -o noclobber
echo Oops >t1
cat t1

exit 0

producing:

% ./s1

(Versions displayed with local utility "version")
GNU bash 2.05b.0

 Create a file:
Hello

 Clobber the file:
Goodbye

 Set protection on:
./s1: line 33: t1: cannot overwrite existing file
Goodbye

See man bash for details.

On my system, noclobber is off by default in bash (I use tcsh for interactive work, and it's on there -- many a file has been saved thereby which otherwise would have be destroyed by a slip of the mind and fingers) ... cheers, drl