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https://github.com/jftuga/mtool

Swiss army knife CLI utility written in Go, using exclusively standard library packages
https://github.com/jftuga/mtool

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Swiss army knife CLI utility written in Go, using exclusively standard library packages

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README 

          
# mtool (multi-tool)



![Code Base: AI Vibes](https://img.shields.io/badge/Code%20Base-AI%20Vibes%20%F0%9F%A4%A0-blue)



`mtool` is a Swiss army knife CLI utility written in Go, using exclusively standard library packages.



## Motivation



The goal of this project was to write a practical CLI tool in Go that incorporates as many standard library modules as feasible without any third-party dependencies. Rather than contriving artificial usage, each package is pulled in naturally through a set of subcommands that solve real, everyday tasks: serving files, fetching URLs, hashing data, inspecting TLS certificates, benchmarking endpoints, converting images and more.



The result is a single-binary multi-tool that leverages **94 unique standard library packages**.



## Disclaimer



This software was developed with the assistance of AI (Anthropic Claude). It is

provided "as is", without warranty of any kind, express or implied. **Use at your

own risk.** The author assumes no liability for any damages arising from its use.



## Installation



**Homebrew**

```bash

brew tap jftuga/homebrew-tap

brew update

brew install jftuga/tap/mtool

```



**Source**

```bash

git clone https://github.com/jftuga/mtool.git

cd mtool

go build -ldflags="-s -w" -o mtool

```



Requires Go 1.26 or later. No third-party dependencies.



## Usage



```

mtool  [options]

```



Run `mtool  -h` for help on any subcommand.



## Subcommands



| Command | Description | Key stdlib packages |

|---|---|---|

| `serve` | Start an HTTP/HTTPS file server with directory listing, optional gzip, and self-signed TLS | `net/http`, `html/template`, `compress/gzip`, `compress/flate`, `embed`, `io/fs`, `mime`, `os/signal`, `context`, `syscall`, `crypto/ecdsa`, `crypto/elliptic`, `crypto/x509/pkix` |

| `fetch` | Fetch a URL and display response details, with cookie support and timing trace | `net/http`, `net/http/httputil`, `net/http/httptrace`, `net/http/cookiejar`, `net/url` |

| `hash` | Compute hashes of files or stdin | `crypto/md5`, `crypto/sha1`, `crypto/sha256`, `crypto/sha512`, `crypto/sha3`, `crypto/hmac`, `hash`, `hash/adler32`, `hash/crc32`, `hash/crc64`, `hash/fnv`, `encoding/hex` |

| `encode` | Encode data (base64, base32, hex, ascii85, URL, quoted-printable, UTF-16) | `encoding/base64`, `encoding/base32`, `encoding/ascii85`, `encoding/hex`, `net/url`, `mime/quotedprintable`, `unicode/utf16` |

| `decode` | Decode data (base64, base32, hex, ascii85, URL, quoted-printable, UTF-16) | `encoding/base64`, `encoding/base32`, `encoding/ascii85`, `encoding/hex`, `net/url`, `mime/quotedprintable`, `unicode/utf16` |

| `info` | Display system and network information in multiple formats | `runtime`, `runtime/debug`, `encoding/json`, `encoding/xml`, `encoding/csv`, `reflect`, `text/tabwriter`, `net`, `net/netip`, `os/user`, `maps` |

| `archive` | Create tar.gz or zip archives | `archive/tar`, `archive/zip`, `compress/gzip`, `path/filepath` |

| `generate` | Generate passwords, tokens, UUIDs, or random data | `crypto/rand`, `math/rand/v2`, `math/big`, `encoding/binary` |

| `bench` | Benchmark an HTTP endpoint with concurrency and percentile stats | `sync`, `sync/atomic`, `container/heap`, `container/list`, `math`, `sort` |

| `inspect` | Inspect TLS certificates or DNS records | `crypto/tls`, `crypto/x509`, `encoding/pem`, `net`, `net/netip` |

| `transform` | Transform text (case, sort, grep, frequency, replace, and more) | `regexp`, `unicode`, `unicode/utf8`, `bufio`, `slices`, `cmp`, `strconv` |

| `image` | Convert images between PNG, JPEG, and GIF formats with dithering | `image`, `image/png`, `image/jpeg`, `image/gif`, `image/draw`, `image/color/palette` |

| `encrypt` | Encrypt a file with AES-256-GCM using a password-derived key | `crypto/aes`, `crypto/cipher`, `crypto/pbkdf2`, `crypto/sha256`, `crypto/rand` |

| `decrypt` | Decrypt a file encrypted with the encrypt command | `crypto/aes`, `crypto/cipher`, `crypto/pbkdf2` |

| `compress` | Compress or decompress data (gzip, zlib, lzw, bzip2) | `compress/bzip2`, `compress/gzip`, `compress/lzw`, `compress/zlib` |



## Examples



### Serve files over HTTP



```bash

mtool serve -addr :9000 -dir ./public -gzip

```



### Serve files over HTTPS with self-signed certificate



```bash

mtool serve -addr :4443 -dir . -tls

# Access with: curl -k https://localhost:4443

```



### Fetch a URL



```bash

mtool fetch -headers https://example.com

mtool fetch -trace https://example.com

mtool fetch -method POST -body '{"key":"val"}' -output response.json https://api.example.com

```



### Hash files



```bash

mtool hash -algo sha256 myfile.txt

echo "hello" | mtool hash -algo md5

mtool hash -algo sha3-256 myfile.txt

mtool hash -algo sha256 -hmac "secret-key" myfile.txt

mtool hash -algo crc64 myfile.txt

mtool hash -algo adler32 myfile.txt

mtool hash -algo fnv64 myfile.txt

```



### Encode and decode



```bash

echo "hello world" | mtool encode -format base64

echo "aGVsbG8gd29ybGQK" | mtool decode -format base64

echo "hello" | mtool encode -format base32

echo "hello" | mtool encode -format ascii85

echo "foo bar" | mtool encode -format url

echo "Héllo wörld" | mtool encode -format qp

echo "H=C3=A9llo" | mtool decode -format qp

echo "hello" | mtool encode -format utf16 > output.utf16

mtool decode -format utf16 output.utf16

```



### System information



```bash

mtool info

mtool info -format json

mtool info -format xml -env

mtool info -format csv

```



### Create archives



```bash

mtool archive -format zip -output backup.zip src/ docs/ README.md

mtool archive -format tar.gz myproject/

mtool archive -format tar.zlib myproject/

mtool archive -extract backup.zip

mtool archive -extract -output ./dest archive.tar.gz

mtool archive -extract archive.tar.bz2

```



### Generate secrets



```bash

mtool generate -mode password -length 32

mtool generate -mode password -length 16 -charset alnum

mtool generate -mode token -length 64

mtool generate -mode uuid -count 5

mtool generate -mode bigint -length 256

```



### Benchmark an HTTP endpoint



```bash

mtool bench -n 500 -c 20 https://example.com

mtool bench -n 1000 -c 50 -method POST https://api.example.com/health

```



### Inspect TLS certificates



```bash

mtool inspect -mode tls google.com

mtool inspect -mode tls -port 8443 internal.example.com

```



### Inspect DNS records



```bash

mtool inspect -mode dns github.com

```



### Transform text



```bash

# Case conversion

echo "hello world" | mtool transform -mode upper

echo "HELLO WORLD" | mtool transform -mode lower



# Sort lines

cat names.txt | mtool transform -mode sort

cat scores.txt | mtool transform -mode sort -numeric -reverse

cat data.txt | mtool transform -mode sort -field 3 -numeric

cat mixed.txt | mtool transform -mode sort -ignore-case



# Search and replace with regex

cat log.txt | mtool transform -mode grep -pattern "ERROR|WARN"

cat messy.txt | mtool transform -mode replace -pattern "\s+" -replacement " "



# Text statistics and word frequency

cat document.txt | mtool transform -mode count

cat document.txt | mtool transform -mode freq



# Deduplicate and reverse

cat dupes.txt | mtool transform -mode uniq

echo "hello" | mtool transform -mode reverse

```



### Convert images



```bash

mtool image photo.png photo.jpg

mtool image -quality 75 screenshot.png compressed.jpg

mtool image photo.jpg photo.gif

mtool image -format png input.gif output.png

```



### Encrypt and decrypt files



```bash

mtool encrypt -password "my-secret" document.pdf document.pdf.enc

mtool decrypt -password "my-secret" document.pdf.enc document.pdf



# Or use an environment variable for the password

export MTOOL_PASSWORD="my-secret"

mtool encrypt document.pdf document.pdf.enc

mtool decrypt document.pdf.enc document.pdf

```



### Compress and decompress



```bash

mtool compress -format gzip largefile.txt largefile.txt.gz

mtool compress -d -format gzip largefile.txt.gz largefile.txt

mtool compress -format zlib data.bin data.bin.zlib

mtool compress -d -format zlib data.bin.zlib data.bin

mtool compress -format lzw data.bin data.bin.lzw

mtool compress -d -format lzw data.bin.lzw data.bin

mtool compress -d -format bzip2 data.bz2 data.txt

mtool compress -level 9 -format gzip archive.tar archive.tar.gz

```



> **Note:** bzip2 supports decompression only (Go's `compress/bzip2` package provides a reader but no writer).



## Standard Library Packages



The following 94 packages from the Go standard library are used:



`archive/tar`, `archive/zip`, `bufio`, `bytes`, `cmp`, `compress/bzip2`, `compress/flate`, `compress/gzip`, `compress/lzw`, `compress/zlib`, `container/heap`, `container/list`, `context`, `crypto/aes`, `crypto/cipher`, `crypto/ecdsa`, `crypto/elliptic`, `crypto/hmac`, `crypto/md5`, `crypto/pbkdf2`, `crypto/rand`, `crypto/sha1`, `crypto/sha256`, `crypto/sha3`, `crypto/sha512`, `crypto/tls`, `crypto/x509`, `crypto/x509/pkix`, `embed`, `encoding/ascii85`, `encoding/base32`, `encoding/base64`, `encoding/binary`, `encoding/csv`, `encoding/hex`, `encoding/json`, `encoding/pem`, `encoding/xml`, `errors`, `flag`, `fmt`, `hash`, `hash/adler32`, `hash/crc32`, `hash/crc64`, `hash/fnv`, `html`, `html/template`, `image`, `image/color/palette`, `image/draw`, `image/gif`, `image/jpeg`, `image/png`, `io`, `io/fs`, `log`, `log/slog`, `maps`, `math`, `math/big`, `math/rand/v2`, `mime`, `mime/quotedprintable`, `net`, `net/http`, `net/http/cookiejar`, `net/http/httptrace`, `net/http/httputil`, `net/netip`, `net/url`, `os`, `os/exec`, `os/signal`, `os/user`, `path`, `path/filepath`, `reflect`, `regexp`, `runtime`, `runtime/debug`, `slices`, `sort`, `strconv`, `strings`, `sync`, `sync/atomic`, `syscall`, `text/tabwriter`, `text/template/parse`, `time`, `unicode`, `unicode/utf16`, `unicode/utf8`



## Tests



Run with `go test -v ./...`



| Test | What it verifies |

|---|---|

| `TestFormatSize` | Byte formatting across B, KB, MB, GB, TB boundaries |

| `TestTLSVersionString` | TLS version code to string mapping, including unknown versions |

| `TestPercentile` | Empty slice, single-element, and various percentile calculations |

| `TestLatencyHeap` | Min-heap property: pop order is ascending |

| `TestGeneratePassword` | Correct length, charset constraints (alpha/alnum/full), category coverage for full charset |

| `TestGenerateToken` | Correct length, hex-only characters, uniqueness across calls |

| `TestGenerateUUID` | V4 format (version nibble = `4`, variant = `[89ab]`), uniqueness across calls |

| `TestGenerateBigInt` | Returns decimal digit strings for various bit widths |

| `TestSortLines` | Alphabetical, reverse, numeric, numeric descending, case-insensitive, field-based, out-of-range field, non-numeric lines in numeric mode |

| `TestPrintTextStats` | Line/word/letter/digit/byte counts, empty input, no-trailing-newline edge case, unicode |

| `TestPrintWordFrequency` | Frequency ordering (most frequent first), case-insensitive folding |

| `TestCreateTarGz` | Round-trip: create tar.gz, read it back, verify file contents |

| `TestCreateZip` | Round-trip: create zip, read it back, verify file contents |

| `TestCreateTarGzDirectory` | Recursive directory archiving preserves structure and nested files |

| `TestLoadDirectoryTemplate` | Embedded template parses and renders with sample data |

| `TestGenerateSelfSignedCert` | Certificate is self-signed, has correct subject/DNS/IP, valid for ~24h, usable by `tls.Config`, unique serial numbers |

| `TestInferImageFormat` | Extension-to-format mapping for png/jpg/jpeg/gif, case insensitivity, unknown extensions |

| `TestEncodeImage_PNG` | PNG encode/decode round-trip preserves dimensions |

| `TestEncodeImage_JPEG` | JPEG encode/decode round-trip preserves dimensions |

| `TestEncodeImage_GIF` | GIF encode/decode round-trip preserves dimensions |

| `TestEncodeImage_Unsupported` | Unsupported format returns an error |

| `TestImageRoundTrip` | Full PNG->JPEG->GIF->PNG conversion chain via `cmdImage`, verifying file output at each step |

| `TestDeriveKey` | Deterministic output, correct key length (32 bytes), different passwords/salts produce different keys |

| `TestEncryptDecryptRoundTrip` | Encrypt then decrypt, verify content matches original, encrypted data differs from plaintext |

| `TestDecryptWrongPassword` | Decryption fails with incorrect password |

| `TestEncryptProducesUniqueOutput` | Same file encrypted twice produces different ciphertext (unique salt/nonce) |

| `TestCompressDecompressGzip` | Gzip round-trip: compress then decompress, verify content matches and compressed size is smaller |

| `TestCompressDecompressZlib` | Zlib round-trip: compress then decompress, verify content matches and compressed size is smaller |

| `TestCompressDecompressBzip2` | Bzip2 decompression: compress with system bzip2, decompress with mtool, verify content matches |

| `TestCompressBzip2RejectsCompress` | Attempting bzip2 compression returns a clear "decompress only" error |

| `TestCompressDecompressLZW` | LZW round-trip with litwidths 6, 7, 8: compress with header, decompress auto-detects litwidth |

| `TestHashAdler32` | Adler-32 hash produces correct output for known input |

| `TestHashCRC64` | CRC-64 hash produces correct output for known input |

| `TestHashFNV` | FNV-32a, FNV-64a, FNV-128a produce correct output lengths for known input |

| `TestEncodeDecodeQuotedPrintable` | Quoted-printable round-trip: encode then decode, verify non-ASCII is encoded and round-trips correctly |

| `TestEncodeDecodeUTF16` | UTF-16 round-trip: encode with BOM then decode, verify content matches including non-ASCII characters |

| `TestEncodeDecodeBase64` | Base64 round-trip: encode then decode, verify content matches |

| `TestEncodeDecodeBase32` | Base32 round-trip: encode then decode, verify content matches |

| `TestEncodeDecodeHex` | Hex round-trip: encode verifies known value, decode restores original |

| `TestEncodeDecodeAscii85` | Ascii85 round-trip: encode then decode, verify content matches |

| `TestEncodeDecodeURL` | URL encoding round-trip: verifies special characters are percent-encoded and decode restores original |

| `TestTransformUpper` | Lowercase text converted to uppercase |

| `TestTransformLower` | Uppercase text converted to lowercase |

| `TestTransformReverse` | String reversal produces correct output |

| `TestTransformGrep` | Regex filtering selects only matching lines |

| `TestTransformReplace` | Regex replacement collapses whitespace correctly |

| `TestTransformUniq` | Deduplication removes repeated lines, preserves order |

| `TestHashAlgorithms` | All hash algorithms (md5, sha1, sha256, sha512, sha3-256, sha3-512, crc32) produce correct hex output lengths |

| `TestHashHMAC` | HMAC differs from plain hash, is deterministic, and different keys produce different output |

| `TestArchiveExtractTarGz` | Create tar.gz then extract, verify extracted file contents match originals |

| `TestArchiveExtractZip` | Create zip then extract, verify extracted file contents match originals |

| `TestCreateTarZlib` | Tar.zlib round-trip: create then extract, verify file contents match |

| `TestCompressGzipLevels` | Gzip level 9 produces smaller output than level 1 for the same input |



## Personal Project Disclosure



This program is my own original idea, conceived and developed entirely:



* On my own personal time, outside of work hours

* For my own personal benefit and use

* On my personally owned equipment

* Without using any employer resources, proprietary information, or trade secrets

* Without any connection to my employer's business, products, or services

* Independent of any duties or responsibilities of my employment



This project does not relate to my employer's actual or demonstrably

anticipated research, development, or business activities. No

confidential or proprietary information from any employer was used

in its creation.