uncompress

Additional Notes

uncompress restores files compressed with the historical compress command, which uses the LZW (Lempel-Ziv-Welch) compression algorithm. Input files have a .Z extension. When decompressing, the .Z suffix is removed unless the -f flag forces overwrite without prompt.

The compress format was widely used on early Unix systems. It has been largely replaced by gzip (.gz), bzip2 (.bz2), and xz (.xz), which offer better compression ratios. The .Z format is still encountered in legacy software distributions and historical Unix archives.

Syntax

uncompress [options] file[.Z]...

Parameters

• file: Compressed file to decompress. The .Z extension is assumed if omitted.

Common Options

• -f, --force: Decompress even if the output file already exists (no prompt).
• -c, --stdout: Write decompressed data to standard output, keeping the original file.
• -v, --verbose: Show the decompression ratio and file names.
• -r, --recursive: Decompress files in directories recursively.

Examples

uncompress file.Z

Decompress file.Z, producing file.

uncompress -c file.Z > output

Decompress to standard output.

uncompress -v archive.Z

Decompress verbosely, showing the compression ratio.

Practical Notes

• gunzip can also decompress .Z files, but gzip is more widely available.
• The compress format is covered by old LZW patents which have since expired.
• zcat is equivalent to uncompress -c and can read .Z files.
• For compatibility, use gunzip or zcat since they handle both .Z and .gz formats.