When processing large files, you should read them in chunks to avoid memory overflow. In Go, you can implement them in the following ways: 1. Use bufio.Scanner to read text files by line, which is suitable for processing logs or CSV files; 2. Use io.ReadFull or Reader.Read to manually control the amount of data read each time, such as 1MB per read, which is suitable for finer control; 3. Use os and bytes.Buffer to cache partial data, which is suitable for scenarios with specific formats while reading, but pay attention to controlling the cache size.
When processing large files, it is obviously not feasible to directly read the entire file into memory at one time, especially in environments with limited memory resources. Go provides a streaming method, which can read large files in chunks to avoid excessive memory usage.
Here are some common and practical practices:
Read using bufio.Scanner chunking
If you want to process text files by line, bufio.Scanner is a very convenient option. It reads 4096 bytes per time by default, automatically helps you with buffering, and supports custom segmentation functions.
The sample code is as follows:
file, err := os.Open("bigfile.txt")
if err != nil {
log.Fatal(err)
}
defer file.Close()
scanner := bufio.NewScanner(file)
for scanner.Scan() {
fmt.Println(scanner.Text()) // Process each line of content}This method is suitable for processing logs, CSVs and other text files in behavior units.
Manually control chunking size using io.ReadFull or Reader.Read
If you need to control the amount of data read more carefully, such as 1MB per read, you can use os.File to io.ReadFull or loop to call Read() method.
Example:
file, _ := os.Open("bigfile.bin")
defer file.Close()
buf := make([]byte, 1024*1024) // Read 1MB each time
for {
n, err := file.Read(buf)
if n == 0 {
break
}
processChunk(buf[:n]) // Custom processing function}Note: This method will not automatically buffer, you need to handle the data boundary issues yourself.
Combining os and bytes.Buffer to cache part of the data
Sometimes you may want to do some temporary storage while reading, such as finding a keyword or parsing a specific format. At this time, you can combine bytes.Buffer as an intermediate cache.
For example:
var buf bytes.Buffer
chunk := make([]byte, 32*1024) // 32KB one piece for {
n, err := reader.Read(chunk)
if n == 0 {
break
}
buf.Write(chunk[:n])
// Determine whether a certain condition is met, such as finding a certain flag bit if containsMagic(buf.Bytes()) {
handleIt(buf.Next(knownLength)) // Extract the target paragraph}
} This method is suitable for reading and processing, but be careful not to let Buffer continue to grow and cause memory overflow.
Basically these are the ways. When choosing different methods in different scenarios, the key is to decide how to "chunk" and "process" according to your actual needs.
The above is the detailed content of How to read a large file in chunks in golang. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
What are the implications of Go's static linking by default?
Jun 19, 2025 am 01:08 AM
Go compiles the program into a standalone binary by default, the main reason is static linking. 1. Simpler deployment: no additional installation of dependency libraries, can be run directly across Linux distributions; 2. Larger binary size: Including all dependencies causes file size to increase, but can be optimized through building flags or compression tools; 3. Higher predictability and security: avoid risks brought about by changes in external library versions and enhance stability; 4. Limited operation flexibility: cannot hot update of shared libraries, and recompile and deployment are required to fix dependency vulnerabilities. These features make Go suitable for CLI tools, microservices and other scenarios, but trade-offs are needed in environments where storage is restricted or relies on centralized management.
How does Go ensure memory safety without manual memory management like in C?
Jun 19, 2025 am 01:11 AM
Goensuresmemorysafetywithoutmanualmanagementthroughautomaticgarbagecollection,nopointerarithmetic,safeconcurrency,andruntimechecks.First,Go’sgarbagecollectorautomaticallyreclaimsunusedmemory,preventingleaksanddanglingpointers.Second,itdisallowspointe
How do I create a buffered channel in Go? (e.g., make(chan int, 10))
Jun 20, 2025 am 01:07 AM
To create a buffer channel in Go, just specify the capacity parameters in the make function. The buffer channel allows the sending operation to temporarily store data when there is no receiver, as long as the specified capacity is not exceeded. For example, ch:=make(chanint,10) creates a buffer channel that can store up to 10 integer values; unlike unbuffered channels, data will not be blocked immediately when sending, but the data will be temporarily stored in the buffer until it is taken away by the receiver; when using it, please note: 1. The capacity setting should be reasonable to avoid memory waste or frequent blocking; 2. The buffer needs to prevent memory problems from being accumulated indefinitely in the buffer; 3. The signal can be passed by the chanstruct{} type to save resources; common scenarios include controlling the number of concurrency, producer-consumer models and differentiation
How can you use Go for system programming tasks?
Jun 19, 2025 am 01:10 AM
Go is ideal for system programming because it combines the performance of compiled languages ??such as C with the ease of use and security of modern languages. 1. In terms of file and directory operations, Go's os package supports creation, deletion, renaming and checking whether files and directories exist. Use os.ReadFile to read the entire file in one line of code, which is suitable for writing backup scripts or log processing tools; 2. In terms of process management, the exec.Command function of the os/exec package can execute external commands, capture output, set environment variables, redirect input and output flows, and control process life cycles, which are suitable for automation tools and deployment scripts; 3. In terms of network and concurrency, the net package supports TCP/UDP programming, DNS query and original sets.
What are functional options patterns in Go, and when are they useful for constructor design?
Jun 14, 2025 am 12:21 AM
FunctionaloptionsinGoareadesignpatternusedtocreateflexibleandmaintainableconstructorsforstructswithmanyoptionalparameters.Insteadofusinglongparameterlistsorconstructoroverloads,thispatternpassesfunctionsthatmodifythestruct'sconfiguration.Thefunctions
How do I call a method on a struct instance in Go?
Jun 24, 2025 pm 03:17 PM
In Go language, calling a structure method requires first defining the structure and the method that binds the receiver, and accessing it using a point number. After defining the structure Rectangle, the method can be declared through the value receiver or the pointer receiver; 1. Use the value receiver such as func(rRectangle)Area()int and directly call it through rect.Area(); 2. If you need to modify the structure, use the pointer receiver such as func(r*Rectangle)SetWidth(...), and Go will automatically handle the conversion of pointers and values; 3. When embedding the structure, the method of embedded structure will be improved, and it can be called directly through the outer structure; 4. Go does not need to force use getter/setter,
What are interfaces in Go, and how do I define them?
Jun 22, 2025 pm 03:41 PM
In Go, an interface is a type that defines behavior without specifying implementation. An interface consists of method signatures, and any type that implements these methods automatically satisfy the interface. For example, if you define a Speaker interface that contains the Speak() method, all types that implement the method can be considered Speaker. Interfaces are suitable for writing common functions, abstract implementation details, and using mock objects in testing. Defining an interface uses the interface keyword and lists method signatures, without explicitly declaring the type to implement the interface. Common use cases include logs, formatting, abstractions of different databases or services, and notification systems. For example, both Dog and Robot types can implement Speak methods and pass them to the same Anno
How do I use the io package to work with input and output streams in Go?
Jun 20, 2025 am 11:25 AM
TheGoiopackageprovidesinterfaceslikeReaderandWritertohandleI/Ooperationsuniformlyacrosssources.1.io.Reader'sReadmethodenablesreadingfromvarioussourcessuchasfilesorHTTPresponses.2.io.Writer'sWritemethodfacilitateswritingtodestinationslikestandardoutpu
