### file-open

#### file-open string

This command will interpret string as a path name to a file and open the file. You may then use the reporters file-read, file-read-line, and file-read-characters to read in from the file, or file-write, file-print, file-type, or file-show to write out to the file.

Note that you can only open a file for reading or writing but not both. The next file i/o primitive you use after this command dictates which mode the file is opened in. To switch modes, you need to close the file using file-close.

Also, the file must already exist if opening a file in reading mode.

When opening a file in writing mode, all new data will be appended to the end of the original file. If there is no original file, a new blank file will be created in its place. (You must have write permission in the file's directory.) (If you don't want to append, but want to replace the file's existing contents, use file-delete to delete it first, perhaps inside a carefully if you're not sure whether it already exists.)

Note that the string can either be a file name or an absolute file path. If it is a file name, it looks in whatever the current directory is. This can be changed using the command set-current-directory. It is defaulted to the model's directory.

    file-open "my-file-in.txt"
    print file-read-line
    => First line in file ;; File is in reading mode
    file-open "C:\\NetLogo\\my-file-out.txt"
    ;; assuming Windows machine
    file-print "Hello World" ;; File is in writing mode

See also file-close.

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