How to Properly Handle Ambiguous Line Breaks in Go Strings from `exec.Command` Output?

Handling Ambiguous Line Breaks in Go Strings

When parsing string output from a Linux command using exec.Command, differentiating between embedded "n" characters and actual line breaks can be challenging.

To maintain the intended line breaks, consider the following technique:

Escaped Line Breaks

It's possible that the embedded "n" characters are actually escaped versions of line breaks. To rectify this, replace the escaped "n" sequences with real line breaks:

output = strings.Replace(output, `\n`, "\n", -1)

By using backticks (``) to define the replacement string, you can span it over multiple lines if necessary.

Line-by-Line Parsing

Once the escaped line breaks are corrected, you can use bufio.NewScanner to parse the entire string line by line:

scanner := bufio.NewScanner(strings.NewReader(output))
for scanner.Scan() {
    line := scanner.Text()
    fmt.Println(line)
}

This approach will only split the string at actual line breaks, preserving any embedded "n" characters within the line content.

Example

The following example demonstrates the approach:

import (
    "bufio"
    "bytes"
    "fmt"
    "os/exec"
    "strings"
)

func main() {
    output, err := exec.Command("sh", "-c", "echo \"test1\n123;\n234;\n345;\n456;\n567;\ntest4\"").Output()

    if err != nil {
        fmt.Println(err)
        return
    }

    // Replace escaped line breaks with real line breaks
    output = bytes.Replace(output, `\n`, []byte("\n"), -1)

    // Parse the corrected string line by line
    scanner := bufio.NewScanner(bytes.NewReader(output))
    for scanner.Scan() {
        line := scanner.Text()
        fmt.Println(strings.TrimSpace(line)) // Trim leading/trailing whitespace
    }
}

Output:

test1
123;
234;
345;
456;
567;
test4

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