Linux CLI 38 🐧 gzip and bzip2 commands - KandZ

gzip file.txt
gzip -d file.txt
gzip -v file.txt file1.txt

bzip2 -k 1.txt
bzip2 -d 1.txt.bz2 
bzip2 -d -f 1.txt.bz2 
bzip2 -k 1.txt 2.txt

gzip and bzip2 are the two classic compression tools on Linux. They both shrink files to save disk space and make transfers faster, and they both work on single files — not directories. The difference is in the trade-off: gzip is fast and widely supported; bzip2 compresses better but is slower.

Key point: Both tools delete the original file by default. Use -k (--keep) to preserve it. Neither can compress a directory directly — you need tar for that, or combine with find.

a – gzip command

gzip is used to compress and decompress files. File compression helps save disk space and transfer files faster. It’s the default compression format on most Linux systems and is recognized almost everywhere.

Important: gzip cannot compress a folder. To compress a directory, you either combine it with find or use tar to bundle it first.

Command	Description
`gzip file.txt`	Compresses one file → `file.txt.gz`
`gzip -d file.txt.gz`	Decompresses one file
`gzip -v file.txt file1.txt`	Compresses multiple files with verbose output
`gzip -k file.txt`	Compresses and keeps the original
`gzip -l file.txt.gz`	Lists compression info
`gzip -r DIR`	Recursively compress files in a directory

How to compress a folder:

# Option 1: find each file and gzip it
find /directory/to/compress -type f -exec gzip {} \;

# Option 2: tar + gzip (the classic combo)
tar -czvf archive.tar.gz /directory/to/compress

# Option 3: pipe a listing through gzip
ls -l /directory/to/compress | gzip > foo.txt.gz

Examples:

# Compress one file
$ gzip file.txt
$ ls -l
-rw-r--r-- 1 kronos kronos 512 Jan 15 10:00 file.txt.gz
# Note: file.txt is gone!

# Decompress
$ gzip -d file.txt.gz
$ ls -l
-rw-r--r-- 1 kronos kronos 1024 Jan 15 10:00 file.txt

# Keep the original
$ gzip -k file.txt
$ ls -l
-rw-r--r-- 1 kronos kronos 1024 Jan 15 10:00 file.txt
-rw-r--r-- 1 kronos kronos  512 Jan 15 10:00 file.txt.gz

# Compress multiple files (verbose)
$ gzip -v file.txt file1.txt
file.txt:    50.0% -- replaced with file.txt.gz
file1.txt:   42.3% -- replaced with file1.txt.gz

# List info about a gzip file
$ gzip -l file.txt.gz
         compressed        uncompressed  ratio uncompressed_name
                512                1024  50.0% file.txt

# Test integrity without decompressing
$ gzip -t file.txt.gz

# Recursively compress all files in a directory
$ gzip -r mydir/
$ ls mydir/
file1.txt.gz  file2.txt.gz  subdir/

# Compress from stdin (no file needed)
$ cat file.txt | gzip > file.txt.gz

# Decompress to stdout without creating a file
$ gzip -dc file.txt.gz
hello world
...

Reading the verbose output:

Field	Meaning
`file.txt`	Original filename
`50.0%`	How much smaller the file got
`replaced with file.txt.gz`	Original was deleted, new file created

Useful options:

Option	Purpose
`-d`	Decompress
`-k`	Keep the original file
`-v`	Verbose
`-l`	List compression info
`-r`	Recursive
`-c`	Write to stdout
`-t`	Test integrity
`-f`	Force (overwrite, compress links)
`-1` … `-9`	Compression level (1=fastest, 9=best)
`-9`	Best compression (default is 6)

Compression levels:

# Fastest, least compression
$ gzip -1 file.txt

# Default
$ gzip file.txt

# Best compression, slowest
$ gzip -9 file.txt

Tip: For text files, gzip typically gets 60–80% reduction. For already-compressed files (.jpg, .mp4, .zip), you’ll see almost no gain — and might even make them bigger.

b – bzip2 command

bzip2 is used to compress and decompress files. Like gzip, bzip2 deletes the original file by default — use -k to keep it. The .bz2 extension shows that a file has been compressed with bzip2.

bzip2 vs gzip:

Aspect	gzip	bzip2
Speed	Fast	Slower
Compression	Good	Better (~10–15% smaller)
Memory use	Low	Higher
Extension	`.gz`	`.bz2`
Ubiquity	Everywhere	Common but less universal

Use bzip2 when: You want the smallest possible file and don’t mind waiting.
Use gzip when: You want speed and universal compatibility.

Command	Description
`bzip2 -k 1.txt`	Compresses a file and keeps the original
`bzip2 -d 1.txt.bz2`	Decompresses a file
`bzip2 -d -f 1.txt.bz2`	Decompresses and overwrites
`bzip2 -k 1.txt 2.txt`	Compresses multiple files into multiple `.bz2` files
`bzmore 1.txt.bz2`	Shows the contents of a compressed file

Examples:

# Compress a file and keep the original
$ bzip2 -k 1.txt
$ ls -l
-rw-r--r-- 1 kronos kronos 1024 Jan 15 10:00 1.txt
-rw-r--r-- 1 kronos kronos  400 Jan 15 10:00 1.txt.bz2

# Decompress a file
$ bzip2 -d 1.txt.bz2
$ ls -l
-rw-r--r-- 1 kronos kronos 1024 Jan 15 10:00 1.txt

# Decompress and overwrite existing file
$ bzip2 -d -f 1.txt.bz2
# -f forces overwrite if 1.txt already exists

# Compress multiple files
$ bzip2 -k 1.txt 2.txt
$ ls -l
-rw-r--r-- 1 kronos kronos 1024 Jan 15 10:00 1.txt
-rw-r--r-- 1 kronos kronos  400 Jan 15 10:00 1.txt.bz2
-rw-r--r-- 1 kronos kronos 2048 Jan 15 10:00 2.txt
-rw-r--r-- 1 kronos kronos  800 Jan 15 10:00 2.txt.bz2

# View a compressed file without decompressing
$ bzmore 1.txt.bz2
------> 1.txt.bz2 <------
hello world
this is the content
...
(END)

# Verbose mode
$ bzip2 -v -k 1.txt
  1.txt:  2.500:1,  3.200 bits/byte, 60.00% saved, 1024 in, 400 out.

# Test integrity
$ bzip2 -t 1.txt.bz2

# Compress to stdout
$ bzip2 -c 1.txt > 1.txt.bz2

# Decompress to stdout
$ bzcat 1.txt.bz2
hello world
...

Useful options:

Option	Purpose
`-d`	Decompress
`-k`	Keep the original file
`-f`	Force (overwrite existing)
`-v`	Verbose
`-t`	Test integrity
`-c`	Write to stdout
`-1` … `-9`	Compression level
`-z`	Compress (default)

Related bzip2 tools:

Tool	Purpose
`bunzip2`	Same as `bzip2 -d`
`bzcat`	Decompress to stdout
`bzmore`	Page through a compressed file
`bzless`	Like `bzmore` with search
`bzgrep`	Search inside a compressed file

Examples with related tools:

# bunzip2 = bzip2 -d
$ bunzip2 1.txt.bz2

# bzcat = decompress to stdout
$ bzcat 1.txt.bz2
hello world
...

# bzgrep = grep inside a compressed file
$ bzgrep "error" log.txt.bz2
2024-01-15 10:30:00 error: connection refused
2024-01-15 10:35:00 error: timeout

# bzless = searchable pager
$ bzless 1.txt.bz2

Tip: The same family exists for gzip: gunzip, zcat, zless, zgrep, zdiff. They’re all convenience wrappers.

Complete Example Session

# ============================================
# PART 1: GZIP BASICS
# ============================================

# Compress a single file
$ ls -l file.txt
-rw-r--r-- 1 kronos kronos 1024 Jan 15 10:00 file.txt

$ gzip file.txt
$ ls -l file.txt.gz
-rw-r--r-- 1 kronos kronos 512 Jan 15 10:00 file.txt.gz
# ✅ file.txt is now file.txt.gz (original removed)

# Decompress
$ gzip -d file.txt.gz
$ ls -l file.txt
-rw-r--r-- 1 kronos kronos 1024 Jan 15 10:00 file.txt

# Keep the original
$ gzip -k file.txt
$ ls -l file.txt file.txt.gz
-rw-r--r-- 1 kronos kronos 1024 Jan 15 10:00 file.txt
-rw-r--r-- 1 kronos kronos  512 Jan 15 10:00 file.txt.gz

# Compress multiple files verbosely
$ gzip -v file.txt file1.txt
file.txt:    50.0% -- replaced with file.txt.gz
file1.txt:   42.3% -- replaced with file1.txt.gz

# List info
$ gzip -l file.txt.gz
         compressed        uncompressed  ratio uncompressed_name
                512                1024  50.0% file.txt

# ============================================
# PART 2: GZIP ON A DIRECTORY
# ============================================

# gzip can't compress a folder directly
$ gzip myfolder/
gzip: myfolder/ is a directory -- ignored

# Option 1: compress each file
$ find myfolder -type f -exec gzip {} \;
$ ls myfolder/
file1.txt.gz  file2.txt.gz  file3.txt.gz

# Option 2: tar + gzip
$ tar -czvf myfolder.tar.gz myfolder/
myfolder/
myfolder/file1.txt
myfolder/file2.txt
myfolder/file3.txt

# ============================================
# PART 3: GZIP LEVELS
# ============================================

$ gzip -1 file.txt         # fastest
$ gzip -9 file.txt         # best compression
$ gzip file.txt            # default (6)

# ============================================
# PART 4: BZIP2 BASICS
# ============================================

# Compress and keep the original
$ bzip2 -k 1.txt
$ ls -l 1.txt 1.txt.bz2
-rw-r--r-- 1 kronos kronos 1024 Jan 15 10:00 1.txt
-rw-r--r-- 1 kronos kronos  400 Jan 15 10:00 1.txt.bz2

# Decompress
$ bzip2 -d 1.txt.bz2
$ ls -l 1.txt
-rw-r--r-- 1 kronos kronos 1024 Jan 15 10:00 1.txt

# Decompress with force
$ bzip2 -d -f 1.txt.bz2

# Compress multiple files
$ bzip2 -k 1.txt 2.txt
$ ls -l 1.txt.bz2 2.txt.bz2
-rw-r--r-- 1 kronos kronos  400 Jan 15 10:00 1.txt.bz2
-rw-r--r-- 1 kronos kronos  800 Jan 15 10:00 2.txt.bz2

# ============================================
# PART 5: BZIP2 VIEWING TOOLS
# ============================================

# View compressed file
$ bzmore 1.txt.bz2
------> 1.txt.bz2 <------
hello world
(END)

# Cat to stdout
$ bzcat 1.txt.bz2
hello world

# Search inside
$ bzgrep "hello" 1.txt.bz2
hello world

# ============================================
# PART 6: COMPARE SIZES
# ============================================

$ ls -l original.txt
-rw-r--r-- 1 kronos kronos 10240 Jan 15 10:00 original.txt

$ gzip -k original.txt
$ ls -l original.txt.gz
-rw-r--r-- 1 kronos kronos 4000 Jan 15 10:00 original.txt.gz

$ bzip2 -k original.txt
$ ls -l original.txt.bz2
-rw-r--r-- 1 kronos kronos 3400 Jan 15 10:00 original.txt.bz2

# bzip2 typically beats gzip by ~10-15%

Quick Reference

gzip

Command	Purpose
`gzip FILE`	Compress a file
`gzip -d FILE.gz`	Decompress
`gzip -k FILE`	Keep the original
`gzip -v FILE`	Verbose
`gzip -l FILE.gz`	List info
`gzip -r DIR`	Recursive
`gzip -t FILE.gz`	Test integrity
`gzip -c FILE > out.gz`	To stdout
`gzip -1` … `-9`	Compression levels

bzip2

Command	Purpose
`bzip2 FILE`	Compress a file
`bzip2 -d FILE.bz2`	Decompress
`bzip2 -k FILE`	Keep the original
`bzip2 -d -f FILE.bz2`	Decompress + overwrite
`bzip2 -v FILE`	Verbose
`bzip2 -t FILE.bz2`	Test integrity
`bzip2 -1` … `-9`	Compression levels

Related Tools

Tool	Purpose
`gunzip`	Same as `gzip -d`
`zcat`	Decompress to stdout
`zless` / `zmore`	Page through `.gz`
`zgrep`	Search inside `.gz`
`bunzip2`	Same as `bzip2 -d`
`bzcat`	Decompress to stdout
`bzless` / `bzmore`	Page through `.bz2`
`bzgrep`	Search inside `.bz2`

gzip vs bzip2

Aspect	gzip	bzip2
Extension	`.gz`	`.bz2`
Speed	Fast	Slower
Compression	Good	Better
Memory	Low	Higher
Compatibility	Universal	Common
Best for	General use	Maximum compression

Best Practices

✅ Do This:

# Use -k to keep the original
gzip -k file.txt                       # ✅
bzip2 -k file.txt                      # ✅

# Use tar for directories
tar -czvf dir.tar.gz dir/              # ✅

# Use -9 for maximum compression
gzip -9 file.txt                       # ✅

# Test integrity after transfer
gzip -t file.txt.gz                    # ✅
bzip2 -t file.txt.bz2                  # ✅

# Use zcat / bzcat to view without extracting
zcat file.txt.gz                       # ✅
bzcat file.txt.bz2                     # ✅

# Combine with find for directories
find dir -type f -exec gzip {} \;      # ✅

❌ Don’t Do This:

# Don't gzip without -k if you need the original
gzip important.txt                     # ❌ deletes original

# Don't try to gzip a directory directly
gzip myfolder/                         # ❌ ignored

# Don't use bzip2 on huge files if speed matters
bzip2 -9 hugefile.iso                  # ❌ slow

# Don't compress already-compressed files
gzip photo.jpg                         # ❌ no gain

# Don't forget -f to overwrite on decompress
bzip2 -d 1.txt.bz2                     # ❌ fails if 1.txt exists

# Don't overwrite originals by mistake
gzip -f file.txt                       # ❌ careful with -f

Common Pitfalls

Pitfall	Problem	Solution
Original file deleted	Surprise data loss	Use `-k`
Can’t compress a directory	gzip refuses	Use `tar` or `find`
No size reduction	Already compressed	Don’t compress `.jpg`, `.mp4`
Decompress fails	File exists	Use `-f` to overwrite
Wrong extension	Confusion	`.gz` vs `.bz2`
Very slow	High compression level	Use lower `-1` … `-9`
Corrupted archive	Bad transfer	`gzip -t` / `bzip2 -t`
Shell glob breaks	Space in filename	Quote the filename

Real-World Examples

1. Compress a Log File

$ gzip -v /var/log/app.log
/var/log/app.log:  85.3% -- replaced with /var/log/app.log.gz

2. Compress and Keep the Original

$ gzip -k important.txt
$ ls -l important.txt*
-rw-r--r-- 1 kronos kronos 10240 Jan 15 10:00 important.txt
-rw-r--r-- 1 kronos kronos  2000 Jan 15 10:00 important.txt.gz

3. Compress a Whole Directory

$ tar -czvf backup.tar.gz /home/kronos/projects/
tar: Removing leading `/' from member names
/home/kronos/projects/
/home/kronos/projects/file1.txt
/home/kronos/projects/file2.txt
...

4. Compress Every File in a Directory

$ find /var/log -type f -name '*.log' -exec gzip {} \;
$ ls /var/log/*.gz
/var/log/syslog.gz  /var/log/auth.log.gz

5. Decompress and View Without Extracting

$ zcat app.log.gz | grep "ERROR"
2024-01-15 10:30:00 ERROR: connection refused

$ bzcat app.log.bz2 | tail -n 20

6. Search Inside a Compressed Log

$ zgrep "ERROR" /var/log/syslog.gz
2024-01-15 10:30:00 ERROR: connection refused
2024-01-15 10:35:00 ERROR: timeout

7. Decompress a `.gz` from a Download

$ wget 'https://example.com/data.txt.gz'
$ gunzip data.txt.gz
$ ls -l data.txt
-rw-r--r-- 1 kronos kronos 1048576 Jan 15 10:00 data.txt

8. Compare gzip and bzip2 Sizes

$ cp bigfile.txt bigfile_gzip.txt
$ cp bigfile.txt bigfile_bzip2.txt

$ gzip bigfile_gzip.txt
$ bzip2 bigfile_bzip2.txt

$ ls -l bigfile.txt bigfile_gzip.txt.gz bigfile_bzip2.txt.bz2
-rw-r--r-- 1 kronos kronos 10240000 Jan 15 10:00 bigfile.txt
-rw-r--r-- 1 kronos kronos  4000000 Jan 15 10:00 bigfile_gzip.txt.gz
-rw-r--r-- 1 kronos kronos  3400000 Jan 15 10:00 bigfile_bzip2.txt.bz2
# bzip2 is ~15% smaller

9. Test an Archive Before Using It

$ gzip -t backup.tar.gz && echo "OK"
OK

$ bzip2 -t backup.tar.bz2 && echo "OK"
OK

10. Stream Compress via a Pipe

$ mysqldump mydb | gzip > mydb.sql.gz
$ tar -cf - mydir/ | bzip2 > mydir.tar.bz2
$ cat access.log | gzip > access.log.gz

11. Compress with Maximum Compression

$ gzip -9 -v archive.txt
archive.txt:  88.0% -- replaced with archive.txt.gz

$ bzip2 -9 -v archive.txt
archive.txt:  89.5% -- replaced with archive.txt.bz2

12. Extract All `.gz` Files in a Directory

$ gunzip *.gz
$ ls
file1.txt  file2.txt  file3.txt

Visual: How gzip and bzip2 Work

┌──────────────────────────────────────────────┐
│         gzip file.txt                        │
│                                              │
│   file.txt (1024 bytes)                      │
│         │                                    │
│         ▼                                    │
│   ┌─────────────────┐                        │
│   │  gzip compress  │                        │
│   └────────┬────────┘                        │
│            │                                 │
│            ▼                                 │
│   file.txt.gz (512 bytes)                    │
│                                              │
│   Original file is REMOVED                   │
│                                              │
└──────────────────────────────────────────────┘

┌──────────────────────────────────────────────┐
│         gzip -k file.txt                     │
│                                              │
│   file.txt (1024 bytes)                      │
│         │                                    │
│         ├──► file.txt (still there)          │
│         │                                    │
│         ▼                                    │
│   file.txt.gz (512 bytes)                    │
│                                              │
│   Original file is KEPT                      │
│                                              │
└──────────────────────────────────────────────┘

┌──────────────────────────────────────────────┐
│         Directory compression                │
│                                              │
│   mydir/                                     │
│   ├── file1.txt                              │
│   ├── file2.txt                              │
│   └── file3.txt                              │
│                                              │
│   ❌ gzip mydir/  (refuses)                  │
│                                              │
│   ✅ tar -czvf mydir.tar.gz mydir/           │
│   ✅ find mydir -type f -exec gzip {} \;     │
│                                              │
└──────────────────────────────────────────────┘

Summary

Command	Purpose	Example
`gzip FILE`	Compress (deletes original)	`gzip file.txt`
`gzip -k FILE`	Compress + keep original	`gzip -k file.txt`
`gzip -d FILE.gz`	Decompress	`gzip -d file.txt.gz`
`gzip -v FILE`	Verbose	`gzip -v file.txt`
`gzip -l FILE.gz`	List info	`gzip -l file.txt.gz`
`gzip -t FILE.gz`	Test integrity	`gzip -t file.txt.gz`
`gzip -1` … `-9`	Compression level	`gzip -9 file.txt`
`gzip -r DIR`	Recursive	`gzip -r mydir/`
`bzip2 FILE`	Compress (deletes original)	`bzip2 1.txt`
`bzip2 -k FILE`	Compress + keep original	`bzip2 -k 1.txt`
`bzip2 -d FILE.bz2`	Decompress	`bzip2 -d 1.txt.bz2`
`bzip2 -d -f FILE.bz2`	Decompress + force	`bzip2 -d -f 1.txt.bz2`
`bzip2 -t FILE.bz2`	Test integrity	`bzip2 -t 1.txt.bz2`
`bzmore FILE.bz2`	View compressed	`bzmore 1.txt.bz2`
`bzcat FILE.bz2`	Decompress to stdout	`bzcat 1.txt.bz2`
`bzgrep PAT FILE.bz2`	Search inside	`bzgrep error log.bz2`
`tar -czvf A.tar.gz DIR`	Directory with gzip	`tar -czvf a.tar.gz dir/`
`tar -cjvf A.tar.bz2 DIR`	Directory with bzip2	`tar -cjvf a.tar.bz2 dir/`

Key takeaways:

gzip and bzip2 compress single files — not directories
Both delete the original by default — use -k to keep it
gzip is fast and universal; bzip2 compresses ~10–15% smaller but slower
Use -d to decompress, -v for verbose, -t to test integrity
For directories, use tar -czvf (gzip) or tar -cjvf (bzip2), or find … -exec gzip
Use zcat, bzcat, zgrep, bzgrep, zless, bzless to work with compressed files without extracting
Compression level -1 is fastest, -9 is best — default is 6
Don’t compress already-compressed files (.jpg, .mp4, .zip) — no gain
Always test archives after transferring them

Remember: gzip and bzip2 both shrink files, but neither handles directories. Keep originals with -k. Use tar when you need to bundle a directory. Use zcat/bzcat when you want to peek inside without extracting. For a quick, universal format, choose gzip. For the smallest possible file and you’re not in a hurry, choose bzip2. Master both, and your disk — and your transfers — will thank you.

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