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🔢 strconv — String ↔ primitive type conversions

Converts between strings and basic data types: integers, floats, and booleans. Essential for parsing command-line arguments, config files, and HTTP query parameters. All parse functions return both a value and an error — always check the error.

Import: import "strconv" | Docs: pkg.go.dev/strconv

📋 Functions, Types & Constants

Name	Signature / Value	Description
strconv.Atoi	func Atoi(s string) (int, error)	Parse decimal string to int (shorthand for ParseInt base 10)
strconv.Itoa	func Itoa(i int) string	Convert int to decimal string
strconv.ParseInt	func ParseInt(s string, base, bitSize int) (int64, error)	Parse string to int64 in given base (2–36)
strconv.ParseUint	func ParseUint(s string, base, bitSize int) (uint64, error)	Parse string to uint64
strconv.ParseFloat	func ParseFloat(s string, bitSize int) (float64, error)	Parse string to float64
strconv.ParseBool	func ParseBool(s string) (bool, error)	Parse '1','t','T','TRUE','true','TRUE','0','f','F' etc.
strconv.FormatInt	func FormatInt(i int64, base int) string	Format int64 as string in given base
strconv.FormatFloat	func FormatFloat(f float64, fmt byte, prec, bitSize int) string	Format float64 as string
strconv.FormatBool	func FormatBool(b bool) string	Return 'true' or 'false'
strconv.AppendInt	func AppendInt(dst []byte, i int64, base int) []byte	Append int64 string to byte slice
strconv.Quote	func Quote(s string) string	Return double-quoted Go string literal
strconv.Unquote	func Unquote(s string) (string, error)	Interpret s as a quoted Go string literal
strconv.ErrRange	var ErrRange error	Returned when value out of range for target type
strconv.ErrSyntax	var ErrSyntax error	Returned when string not in expected format

💡 Example Program

Save as main.go inside any directory and run with go run main.go. No extra packages to install — all standard library.

package main

import (
    "fmt"
    "strconv"
)

func main() {
    // String → int
    n, err := strconv.Atoi("42")
    if err != nil {
        fmt.Println("Error:", err)
    } else {
        fmt.Printf("Atoi: %d  (type %T)\n", n, n)
    }

    // int → string
    s := strconv.Itoa(12345)
    fmt.Printf("Itoa: %q\n", s)

    // ParseFloat
    f, err := strconv.ParseFloat("3.14159", 64)
    if err == nil {
        fmt.Printf("ParseFloat: %.5f\n", f)
    }

    // ParseBool
    b, _ := strconv.ParseBool("true")
    fmt.Printf("ParseBool: %v\n", b)

    // ParseInt with base
    hex, _ := strconv.ParseInt("FF", 16, 64)
    bin, _ := strconv.ParseInt("1010", 2, 64)
    fmt.Printf("ParseInt hex=0xFF → %d\n", hex)
    fmt.Printf("ParseInt bin=1010 → %d\n", bin)

    // FormatFloat
    fs := strconv.FormatFloat(3.14159265, 'f', 4, 64)
    fmt.Println("FormatFloat:", fs)

    // Error handling best practice
    if _, err := strconv.Atoi("not_a_number"); err != nil {
        fmt.Println("Expected error:", err)
    }

    // Quote / Unquote
    quoted := strconv.Quote("Hello\tWorld\n")
    fmt.Println("Quoted:", quoted)
    unquoted, _ := strconv.Unquote(quoted)
    fmt.Println("Unquoted:", unquoted)
}
// go run main.go

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