How to gunzip without overwriting non-interactively

Question

I want to unzip .gz files but without overwriting. When the resulting file exists, gunzip will ask for permission to overwrite, but I want gunzip not to overwrite by default and just abort. I read in a man that -f force overwriting, but I haven't found nothing about skipping it.

gunzip ${file}

I need something like -n in copying cp -n ${file}

your question is not very clear. By default gunzip will not overwrite existing files. — Chris Maes, Jun 03 '14 at 09:54
okay, so you want non-interactive gunzip that does not overwrite? — Chris Maes, Jun 03 '14 at 09:58
if so, the answer of konsolebox will do just fine... and you can accept it if it does what you want. If not, please make your question more clear — Chris Maes, Jun 03 '14 at 10:00
yes his answer is ok, but I have to wait 5 min to accept it ;) — herder, Jun 03 '14 at 10:04

score 26 · Answer 1 · answered Jun 03 '14 at 10:02

26

gunzip will prompt you before overwriting a file. You can use the yes command to automatically send an n string to the gunzip prompt, as shown below:

$ yes n | gunzip file*.gz
gunzip: file already exists;    not overwritten
gunzip: file2 already exists;    not overwritten

answered Jun 03 '14 at 10:02

dogbane

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how do I send a `y` to overwrite without a prompt? – seralouk Nov 29 '22 at 15:43
This causes a broken pipe – seralouk Nov 29 '22 at 19:33
@seralouk, as the the manual, you can use the --force flag: gunzip -f file*.gz – iquestionshard Mar 16 '23 at 11:56

score 8 · Accepted Answer · answered Jun 03 '14 at 09:51

Granting your files have .gz extensions, you can check if the file exists before running gunzip:

[[ -e ${file%.gz} ]] || gunzip "${file}"

[[ -e ${file%.gz} ]] removes .gz and checks if a file having its name exists. If not (false), || would run gunzip "${file}".

score 3 · Answer 3 · edited Mar 20 '17 at 10:04

Here's a combination of the answers here and this that will unzip a group of gzipped files to a different destination directory:

dest="unzipped"
for f in *.gz; do
  STEM=$(basename "${f}" .gz)
  unzipped_name="$dest/$STEM"
  echo ''
  echo gunzipping $unzipped_name
  if [[ -e $unzipped_name ]]; then
    echo file exists
  else
    gunzip -c "${f}" > $unzipped_name
    echo done
  fi
done

How to gunzip without overwriting non-interactively

3 Answers3