How to create temporary files in go

When programming in python, one of the common modules I used often is the tempfile module. This module contains functions which create temporary files and returns a file object. This is useful if you are downloading large files and want to cleanup automatically once you are done.

Go has similar functions. Lets look at a sample code which create temporary folders and files and writes to it.

Here is the example source code of the program.

package main

import (
    "fmt"
    "io/ioutil"
    "os"
)

func main() {

    // Create a Temp File:  This will create a filename like /tmp/pre-23423234
    // If we use a pattern like "pre-*.ext", you can get a file like: /tmp/pre-23423234.ext
    tmpFile, err := ioutil.TempFile(os.TempDir(), "pre-")
    if err != nil {
        fmt.Println("Cannot create temporary file", err)
    }

    // cleaning up by removing the file
    defer os.Remove(tmpFile.Name())

    fmt.Println("Created a Temp File: " + tmpFile.Name())

    // Write to the file
    text := []byte("Writing some text into the temp file.")
    if _, err = tmpFile.Write(text); err != nil {
        fmt.Println("Failed to write to temporary file", err)
    }

    // Close the file
    if err := tmpFile.Close(); err != nil {
        fmt.Println(err)
    }
}

The io/ioutil package contains two function TempDir and TempFile to create a temporary directory and a temporary file.

By default on a unix machine, the TempDir function returns /tmp/ as the temporary directory. You can pass in additional parameters to create directories with prefixes.

The TempFile function creates a unique and random number. You can control the prefix and suffix of the file with the pattern parameter. By passing example-*.tmp, you will create temporary files. This is useful if you don’t want to delete the temporary files in the program, but instead want to have a batch delete job which cleans up the temporary files later.

Once the file is created, you can write anything into the file as it is of type os.File. And since os.File implements the io.ReadWriter interface, you can write into the file using the Write method.

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