Working with files

To work with files, we need the IOStream type. IOStream is a type with the IO supertype and has the following characteristics:

• The fields are given by fieldnames(IOStream):

(:handle, :ios, :name, :mark)  

• The types are given by IOStream.types:

(Ptr{Nothing}, Array{UInt8,1}, AbstractString, Int64)

The file handle is a pointer of the Ptr type, which is a reference to the file object.

Opening and reading a line-oriented file with the example.dat name is very easy:

// code in Chapter 8\io.jl 
fname = "example.dat"
f1 = open(fname) 

fname is a string that contains the path to the file, using the escaping of special characters with \ when necessary. For example, in Windows, when the file is in the test folder on the D: drive, this would become d:\\test\\example.dat. The f1 variable is now an IOStream(<file example.dat>) object.

To read all lines one after another in an array, use data = readlines(f1), which returns 3-element Array{String,1}:

"this is line 1."
"42; 3.14"
"this is...