File i/o in Go

Printing in Golang

Go has many ways to print. All printing functions stem from the fmt package.

There are 3 families of printing functions:

First family

• fmt.Println prints to os.Stdout by default
• fmt.Printf allows you to format the string. For example %d is the format code for integers.

Second family

• fmt.Fprintln can define an output identifier. For example os.Stdout
• fmt.Fprintf can define an output identifier. And also format the string.

Third family

• fmt.Sprintln outputs a string to a variable instead of an output identifier
• fmt.Sprintf outputs to a string but also format the string.

File I/O Packages

1. Os package: has functions to open and create files, list directories etc… and has the File type
2. Io package: has utilities to read and write
3. Bufio pakcage: provides buffered i/o scanners etc…
4. Io/ioutil package: has extra utilities such as reading and an entire file to memory, or writing it all out at once
5. Strconv package: has utilities to convert to/from string representations

Misc commands for files:

• Opening a file: os.Open(fname)
• Copying from a file to standard output: io.Copy(os.Stdout, file)
• Reading all the data from a file (without buffering): ioutil.ReadAll(file)
• Using bufio to scan a file:

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scan := bufio.NewScanner(file)
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for scan.Scan() {
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//this will by default iterate over every line in the file
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}