| Throughout program execution, we often want to create data that isn't needed after the program exits. *Temporary files and directories* are useful for this purpose since they don't pollute the file system over time. | ||
package main |
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import ( |
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"fmt" |
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"io/ioutil" |
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"os" |
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"path/filepath" |
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) |
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func check(e error) { |
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if e != nil { |
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panic(e) |
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} |
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} |
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func main() { |
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| The easiest way to create a temporary file is by calling `ioutil.TempFile`. It creates a file *and* opens it for reading and writing. We provide `""` as the first argument, so `ioutil.TempFile` will create the file in the default location for our OS. | f, err := ioutil.TempFile("", "sample") |
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check(err) |
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| Display the name of the temporary file. On Unix-based OSes the directory will likely be `/tmp`. The file name starts with the prefix given as the second argument to `ioutil.TempFile` and the rest is chosen automatically to ensure that concurrent calls will always create different file names. | fmt.Println("Temp file name:", f.Name()) |
Temp file name: /tmp/sample882786001 |
| Clean up the file after we're done. The OS is likely to clean up temporary files by itself after some time, but it's good practice to do this explicitly. | defer os.Remove(f.Name()) |
Temp file name: /tmp/sample363271939 |
| We can write some data to the file. | _, err = f.Write([]byte{1, 2, 3, 4}) |
Temp file name: /tmp/sample453381763 |
check(err) |
Temp file name: /tmp/sample829496240 |
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| If we intend to write many temporary files, we may prefer to create a temporary *directory*. `ioutil.TempDir`'s arguments are the same as `TempFile`'s, but it returns a directory *name* rather than an open file. | dname, err := ioutil.TempDir("", "sampledir") |
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check(err) |
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fmt.Println("Temp dir name:", dname) |
Temp file name: /tmp/sample342032679 Temp dir name: /tmp/sampledir482562650 |
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defer os.RemoveAll(dname) |
Temp file name: /tmp/sample287732029 Temp dir name: /tmp/sampledir071331192 |
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| Now we can synthesize temporary file names by prefixing them with our temporary directory. | fname := filepath.Join(dname, "file1") |
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err = ioutil.WriteFile(fname, []byte{1, 2}, 0666) |
Temp file name: /tmp/sample596892995 Temp dir name: /tmp/sampledir426724806 |
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check(err) |
Temp file name: /tmp/sample268478350 Temp dir name: /tmp/sampledir635324309 |
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} |
Temp file name: /tmp/sample190893423 Temp dir name: /tmp/sampledir121832450 |