# gzip — Fast File Compression

> Practical guide to gzip: compress, decompress and test files with LZ77 — plus zcat, zgrep, zless and pigz for everyday use.

Source: https://www.jpkc.com/db/en/cheatsheets/archives/gzip/

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gzip is the classic Unix compression tool and squeezes single files using the fast LZ77 algorithm. You reach for it daily on logs, database dumps or as the backend of `tar`. One important gotcha: gzip **replaces** the original file with the `.gz` version by default – without `-k` the original is gone afterwards. This guide walks you through compressing, decompressing and testing, plus the helpers `zcat`, `zgrep` and the parallel `pigz`.
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## Compress

`gzip <file>` — Compress a file (replaces original with .gz version).

```bash
gzip access.log
```

`gzip -k <file>` — Compress and keep the original file.

```bash
gzip -k access.log
```

`gzip -<level> <file>` — Compress with a specific level (1=fastest, 9=best compression).

```bash
gzip -9 access.log
```

`gzip -r <directory>` — Recursively compress all files in a directory.

```bash
gzip -r /var/log/old/
```

`gzip -c <file> > <output.gz>` — Compress to stdout, allowing custom output filename.

```bash
gzip -c data.json > data.json.gz
```

## Decompress

`gzip -d <file.gz>` — Decompress a gzipped file.

```bash
gzip -d access.log.gz
```

`gunzip <file.gz>` — Decompress a gzipped file (same as gzip -d).

```bash
gunzip access.log.gz
```

`gzip -dk <file.gz>` — Decompress and keep the compressed file.

```bash
gzip -dk access.log.gz
```

`gunzip -r <directory>` — Recursively decompress all .gz files in a directory.

```bash
gunzip -r /var/log/old/
```

`gzip -dc <file.gz> > <output>` — Decompress to stdout with custom output filename.

```bash
gzip -dc backup.sql.gz > backup.sql
```

## Information & Testing

`gzip -l <file.gz>` — List compression info: compressed/uncompressed size, ratio, name.

```bash
gzip -l access.log.gz
```

`gzip -t <file.gz>` — Test the integrity of a compressed file.

```bash
gzip -t backup.sql.gz
```

`gzip -v <file>` — Verbose mode. Show filename and compression ratio.

```bash
gzip -v access.log
```

## Batch Operations

`gzip *.log` — Compress all .log files in the current directory.

```bash
gzip *.log
```

`gunzip *.gz` — Decompress all .gz files in the current directory.

```bash
gunzip *.gz
```

`find . -name '*.log' -exec gzip {} \;` — Find and compress all .log files recursively.

```bash
find /var/log -name '*.log' -exec gzip {} \;
```

`find . -name '*.gz' -mtime +30 -delete` — Delete compressed files older than 30 days.

```bash
find /var/log -name '*.gz' -mtime +30 -delete
```

## Related Tools

`zcat <file.gz>` — View contents of a gzipped file without decompressing.

```bash
zcat access.log.gz
```

`zgrep <pattern> <file.gz>` — Search inside a gzipped file without decompressing.

```bash
zgrep "404" access.log.gz
```

`zless <file.gz>` — Page through a gzipped file with less.

```bash
zless access.log.gz
```

`zdiff <file1.gz> <file2.gz>` — Compare two gzipped files without decompressing.

```bash
zdiff old.log.gz new.log.gz
```

`pigz <file>` — Parallel gzip compression using multiple CPU cores.

```bash
pigz largefile.sql
```

`pigz -d <file.gz>` — Parallel gzip decompression.

```bash
pigz -d largefile.sql.gz
```

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## Conclusion

gzip is fast, available everywhere and ideal for single files such as logs or dumps. Always remember that it replaces the original – use `-k` when you want to keep it, and `gzip -t` before you rely on an archive. gzip has no container for multiple files: to pack a whole directory into one file, combine it with `tar` (`tar czf`), and for large data sets the parallel `pigz` pays off.

## Further Reading

- [GNU gzip – official project page](https://www.gnu.org/software/gzip/) – downloads, manual and release notes
- [GNU gzip Manual](https://www.gnu.org/software/gzip/manual/) – complete reference of all options
- [gzip – Wikipedia](https://en.wikipedia.org/wiki/Gzip) – background on the format, history and LZ77
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## Related Commands

- [7z](https://www.jpkc.com/db/en/cheatsheets/archives/7z/) – high-ratio archiver with its own .7z format
- [tar](https://www.jpkc.com/db/en/cheatsheets/archives/tar/) – bundles many files into one archive, often paired with gzip
- [zip](https://www.jpkc.com/db/en/cheatsheets/archives/zip/) – cross-platform archive format with compression in one step