csvlint (Rust)

A fast CSV linter written in Rust that validates CSV files according to RFC 4180.

Installation

From source

git clone https://github.com/blackstar257/csvlint-rs
cd csvlint-rs
cargo build --release

The binary will be available at target/release/csvlint.

Using Cargo

cargo install csvlint

Usage

csvlint [OPTIONS] <FILE>

Arguments

• <FILE> - The CSV file to validate

Options

• -d, --delimiter <DELIMITER> - Field delimiter in the file (default: ",")
  • Supports: , (comma), \t (tab), | (pipe), : (colon), ; (semicolon)
• -l, --lazyquotes - Try to parse improperly escaped quotes
• --rfc4180 - Strict RFC 4180 compliance mode (enforces comma delimiter and CRLF line endings)
• -h, --help - Print help information
• -V, --version - Print version information

Examples

# Validate a standard CSV file
csvlint data.csv

# Validate with strict RFC 4180 compliance (comma delimiter, CRLF line endings)
csvlint --rfc4180 data.csv

# Validate a tab-separated file
csvlint --delimiter '\t' data.tsv

# Validate a pipe-separated file
csvlint --delimiter '|' data.txt

# Validate with lazy quote parsing (more lenient)
csvlint --lazyquotes data.csv

Exit Codes

• 0 - File is valid
• 1 - File does not exist or parsing was halted due to fatal errors
• 2 - File contains validation errors

Features

• Full RFC 4180 Compliance: Validates CSV files according to the RFC 4180 standard
  • Strict mode: Enforces CRLF line endings and comma delimiters
  • Line ending validation: Checks for proper CRLF (\r\n) line endings
  • Quote escaping validation: Ensures proper quote doubling for escapes
• Multiple Delimiters: Supports comma, tab, pipe, colon, and semicolon delimiters
• Detailed Error Reports: Provides specific error messages with record numbers and error categories
• Field Count Validation: Ensures all records have the same number of fields as the header
• Quote Validation: Detects improperly quoted fields and bare quotes
• Lazy Quote Mode: Optional mode to parse files with improperly escaped quotes
• Fast Performance: Built with Rust for maximum performance using the csv crate
• Memory Efficient: Processes files without loading everything into memory

Error Types

The linter detects several types of CSV format violations:

• Field Count Errors: Records with different number of fields than the header
• Line Ending Errors: Invalid line endings (RFC 4180 requires CRLF)
• Quote Errors: Improperly quoted fields, bare quotes, unterminated quotes
• Unescaped Special Characters: Special characters not properly escaped or quoted
• Encoding Errors: Invalid UTF-8 sequences
• I/O Errors: File reading errors

Library Usage

This tool can also be used as a Rust library:

[dependencies]
csvlint = "0.1.0"

use csvlint::validate;
use std::fs::File;
use std::io::BufReader;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let file = File::open("data.csv")?;
    let reader = BufReader::new(file);

    let result = validate(reader, b',', false)?;

    if result.errors.is_empty() {
        println!("File is valid!");
    } else {
        for error in result.errors {
            println!("{}", error);
        }
    }

    Ok(())
}

Development

Building

cargo build

Testing

cargo test

Running integration tests

cargo test integration_tests

RFC 4180 Compliance

This implementation provides comprehensive support for RFC 4180 compliance:

Strict Mode (--rfc4180)

When using the --rfc4180 flag, the linter enforces:

• Line Endings: Must be CRLF (\r\n) as specified in RFC 4180
• Delimiter: Must be comma (,) only
• Quote Escaping: Strict validation of quote doubling (e.g., "He said ""Hello"".")
• Field Structure: Consistent field count across all records

Standard Mode (default)

In standard mode, the linter is more lenient and accepts:

• Various line endings (LF, CRLF, CR)
• Multiple delimiter types
• More flexible quote handling with --lazyquotes

Compliance Features

• ✅ CRLF Line Endings: Validates proper \r\n line endings
• ✅ Field Count Consistency: Ensures all records have same field count
• ✅ Quote Escaping: Validates doubled quotes within quoted fields
• ✅ Special Character Handling: Validates proper quoting of fields containing commas, quotes, or line breaks
• ✅ Header Support: Optional header row support
• ✅ MIME Type Compliance: Follows text/csv MIME type specification

Performance

This Rust implementation leverages the excellent csv crate for parsing, which provides:

• Zero-copy parsing where possible
• Efficient memory usage
• Fast field iteration
• Robust error handling

License

MIT License - see LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.