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Developer Methods for Text to CSV

A central hub of code examples for converting text files to CSV across languages — R, Java, C# and C, with quick starters here and full guides for each. Includes notes on choosing the right CSV library.

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Overview

Convert text to CSV in any language

Written by the TextToCSV team Updated June 2026 How we test

Every language can read delimited text and write CSV; the differences are in the libraries that handle quoting and encoding correctly. This hub links the full guides and shows a minimal starter for each, so you can pick the right approach for R, Java, C#, C and the scripting options.

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Full step-by-step guides with runnable code:

Minimal starters

Quick “tab-delimited in, comma CSV out” snippets — see each guide for quoting, encoding and batch handling.

R — base

df <- read.delim("input.txt")          # tab-delimited
write.csv(df, "output.csv", row.names = FALSE)

Java — OpenCSV

import com.opencsv.*;
import java.io.*;

try (CSVReader r = new CSVReaderBuilder(new FileReader("input.txt"))
        .withCSVParser(new CSVParserBuilder().withSeparator('\t').build()).build();
     CSVWriter w = new CSVWriter(new FileWriter("output.csv"))) {
    String[] row;
    while ((row = r.readNext()) != null) w.writeNext(row);
}

C# — CsvHelper

using var reader = new StreamReader("input.txt");
using var csvIn = new CsvHelper.CsvReader(reader,
    new CsvHelper.Configuration.CsvConfiguration(System.Globalization.CultureInfo.InvariantCulture){ Delimiter = "\t" });
using var writer = new StreamWriter("output.csv");
using var csvOut = new CsvHelper.CsvWriter(writer, System.Globalization.CultureInfo.InvariantCulture);
csvOut.WriteRecords(csvIn.GetRecords<dynamic>());

C — fgets / strtok

#include <stdio.h>
#include <string.h>

int main(void) {
    FILE *in = fopen("input.txt", "r"), *out = fopen("output.csv", "w");
    char line[4096];
    while (fgets(line, sizeof line, in)) {
        line[strcspn(line, "\r\n")] = 0;
        char *tok = strtok(line, "\t");
        int first = 1;
        while (tok) { fprintf(out, "%s%s", first ? "" : ",", tok); first = 0; tok = strtok(NULL, "\t"); }
        fputc('\n', out);
    }
    fclose(in); fclose(out);
    return 0;
}

Choosing a CSV library

For anything beyond trivial data, prefer a real CSV library over manual string splitting, because correct quoting and embedded-newline handling are easy to get wrong:

Python — the built-in csv module, or pandas for analysis.
R — readr or data.table::fread/fwrite for speed.
Java — OpenCSV or Apache Commons CSV.
C# — CsvHelper.
C — usually hand-rolled; budget for quoting if fields can contain commas.

Good to know

Principles that apply in every language

Whatever language you choose, the same handful of principles keep text-to-CSV conversions correct. Treat encoding explicitly — read and write UTF-8, and add a BOM only when Excel is the consumer. Use a real CSV library rather than string splitting whenever fields might contain the delimiter, a quote or a newline, because hand-rolled parsers almost always get those edge cases wrong. Preserve identifier columns as text so leading zeros are not lost, and stream large files line by line instead of loading them whole.

Finally, build a verification step into any script: re-read the output you just wrote and confirm the row and column counts match what you expected. That tiny round-trip check is the single most effective guard against silent data corruption, and it works identically in Python, R, Java, C#, C and the shell.

One more shared lesson: keep the conversion logic in a small, well-tested function with a clear input and output, separate from file handling and any interface. That makes it trivial to unit-test against awkward inputs — embedded delimiters, empty fields, mixed encodings — and to reuse the same routine in a script, a service or a batch job without rewriting it for each context.

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