String Template Processor

A flexible, composable string transformation CLI tool and Rust library. string_pipeline lets you chain operations like split, join, slice, replace, case conversion, trim, and more, using a concise template syntax. It is ideal for quick text manipulation, scripting, and data extraction.

Table of Contents

• Features
• Crate
• Installation
  • CLI
  • Library
• Usage
  • As a CLI
  • As a Library
• Template Syntax
  • Syntax Reference
  • Supported Operations
  • Range Specifications
  • Escaping
  • Debug Mode
• Examples
• Testing
• Contributing
• License

Features

• Composable operations: Chain multiple string operations in a single template.
• Split and join: Extract and reassemble parts of strings.
• Slice and range: Select sub-strings or sub-lists by index or range.
• Regex replace: sed-like regex search and replace.
• Case conversion: Uppercase and lowercase.
• Trim and strip: Remove whitespace or custom characters.
• Append and prepend: Add text before or after.
• Escaping: Use \: and \\ to include literal colons and backslashes in arguments.
• Flexible indices: Python-like negative indices in ranges and slices with Rust-like syntax.
• Stdin support: Read input from stdin when no input argument is provided.
• Debug mode: Add ! after { to print debug info for each operation.
• Robust error handling: Helpful error messages for invalid templates or arguments.
• Tested: Comprehensive test suite.

Crate

Find the crate on crates.io:

[dependencies]
string_pipeline = "0.6.0"

Installation

CLI

Clone and build:

git clone https://github.com/lalvarezt/string_pipeline.git
cd string_pipeline
cargo build --release

Or run directly with Cargo:

cargo run -- "{template}" "input string"

Library

Add to your Cargo.toml as shown above.

Usage

As a CLI

# With input argument
string-pipeline "{template}" "input string"

# With stdin input
echo "input string" | string-pipeline "{template}"

Examples:

# Get the second item in a comma-separated list
string-pipeline "{split:,:1}" "a,b,c"
# Output: b

# Replace all spaces with underscores and uppercase
string-pipeline "{replace:s/ /_/g|upper}" "foo bar baz"
# Output: FOO_BAR_BAZ

# Trim, split, and append
string-pipeline "{split:,:..|trim|append:!}" " a, b,c , d , e "
# Output: a!,b!,c!,d!,e!

# Using stdin for processing file content
cat data.txt | string-pipeline "{split:\n:..|trim|prepend:- }"

As a Library

use string_pipeline::process;

fn main() {
    let result = process("a,b,c", "{split:,:..|join:\\n}").unwrap();
    assert_eq!(result, "a\nb\nc");
}

Template Syntax

Templates are enclosed in {} and consist of a chain of operations separated by |. Arguments to operations are separated by :.

Syntax Reference

• Template: { [!] operation_list? }
  • Add ! after { to enable debug mode.
• Operation List: operation ('|' operation)*
• Operation:
  • split:<sep>:<range>
  • join:<sep>
  • slice:<range>
  • replace:s/<pattern>/<replacement>/<flags>
  • upper
  • lower
  • trim
  • strip:<chars>
  • append:<suffix>
  • prepend:<prefix>
  • Shorthand for split:
    • {index} (e.g. {1})
    • {range} (e.g. {1..3})

Supported Operations

Range Specifications

Ranges use Rust-like syntax and support negative indices like Python:

Negative indices count from the end:

• -1 = last element
• -2 = second to last element
• -3.. = last 3 elements

Escaping

To include a literal:

• Use \: for a literal colon in arguments.
• Use \\ for a literal backslash.
• Use \n, \t, \r for newline, tab, carriage return.
• Use \| for a literal pipe in arguments.

Enable Debug Mode

• Add ! after { to enable debug output for each operation:
  • Example: {!split:,:..|upper|join:-}

Examples

Basic

# Get the last item
string-pipeline "{split:,:-1}" "a,b,c"
# Output: c

# Get a range of items
string-pipeline "{split:,:1..=3}" "a,b,c,d,e"
# Output: b,c,d

# Replace 'foo' with 'bar' globally
string-pipeline "{replace:s/foo/bar/g}" "foo foo"
# Output: bar bar

# Chain operations: uppercase, then append
string-pipeline "{upper|append:!}" "hello"
# Output: HELLO!

# Prepend with a colon (escaped)
string-pipeline "{prepend:\:foo}" "bar"
# Output: :foobar

Advanced

# Complex chaining: split, select range, join, replace, uppercase
string-pipeline "{split:,:0..2|join:-|replace:s/a/X/|upper}" "a,b,c"
# Output: X-B

# Slice string characters
string-pipeline "{slice:1..=3}" "hello"
# Output: ell

# Split, trim each item, then prepend
echo " a , b , c " | string-pipeline "{split:,:..|trim|prepend:item_}"
# Output: item_a,item_b,item_c

# Strip custom characters
string-pipeline "{strip:xy}" "xyhelloxy"
# Output: hello

Real-World

# Process CSV-like data
echo "name,age,city" | string-pipeline "{split:,:1..}"
# Output: age,city

# Format file paths
echo "/home/user/documents/file.txt" | string-pipeline "{split:/:-1}"
# Output: file.txt

# Extract file extension
echo "document.pdf" | string-pipeline "{split:.:-1|upper}"
# Output: PDF

# Process log entries with timestamps
echo "2023-01-01 ERROR Failed to connect" | string-pipeline "{split: :1..|join: |lower}"
# Output: error failed to connect

Shorthand

# Get the second word (space-separated)
string-pipeline "{1}" "foo bar baz"
# Output: bar

# Get a range of words
string-pipeline "{1..3}" "foo bar baz qux"
# Output: bar baz

Debug Mode

# Print debug info for each operation
string-pipeline "{!split:,:..|upper|join:-}" "a,b,c"
# DEBUG: Initial value: Str("a,b,c")
# DEBUG: Applying operation 1: Split { sep: ",", range: Range(None, None, false) }
# DEBUG: Result: List with 3 items:
# DEBUG:   [0]: "a"
# DEBUG:   [1]: "b"
# DEBUG:   [2]: "c"
# DEBUG: ---
# DEBUG: Applying operation 2: Upper
# DEBUG: Result: List with 3 items:
# DEBUG:   [0]: "A"
# DEBUG:   [1]: "B"
# DEBUG:   [2]: "C"
# DEBUG: ---
# DEBUG: Applying operation 3: Join { sep: "-" }
# DEBUG: Result: String("A-B-C")
# DEBUG: ---
# A-B-C

Testing

Run the test suite:

cargo test

Contributing

Contributions and suggestions are welcome! Please open issues or pull requests on GitHub.

License

This project is licensed under the MIT License. See LICENSE for details.

Enjoy fast, composable string transformations!