File Reader

This node can be used to read data from an ASCII file or URL location. It can be configured to read various formats.
When you open the node's configuration dialog and provide a filename, it tries to guess the reader's settings by analyzing the content of the file. Check the results of these settings in the preview table. If the data shown is not correct or an error is reported, you can adjust the settings manually (see below).

The file analysis runs in the background and can be cut short by clicking the "Quick scan", which shows if the analysis takes longer. In this case the file is not analyzed completely, but only the first fifty lines are taken into account. It could happen then, that the preview appears looking fine, but the execution of the File Reader fails, when it reads the lines it didn't analyze. Thus it is recommended you check the settings, when you cut an analysis short.

Note: In case this node is used in a loop, make sure that all files have the same format (e. g. separators, column headers, column types). The node saves the configuration only during the first execution.
Alternatively, the CSV Reader node can be used as it checks the configuration in every iteration of a loop.

Options

ASCII file location

Enter a valid file name or URL. When you press ENTER, the file is analyzed and the settings pre-set. You can also choose a previously read file from the drop-down list, or select a file from the "Browse..." dialog.

Preserve user settings

If checked, the checkmarks and column names/types you explicitly entered are preserved even if you select a new file. By default, the analyzer starts with fresh default settings for each new file location.

Rescan

If clicked, the file content is analyzed again. All settings are reset (unless the "Preserve user settings" option is selected) and the file is read in again to pre-set new settings and the table structure.

Read row IDs

If checked, the first column in the file is used as row IDs. If not checked, default row headers are created.

Read column headers

If checked, the items in the first line of the file are used as column names. Otherwise default column names are created.

Column delimiter

Enter the character(s) that separate the data tokens in the file, or select a delimiter from the list.

Ignore spaces and tabs

If checked, spaces and the TAB characters are ignored (not in quoted strings though).

Java style comment

Everything between '/*' and '*/' is ignored. Also everything after '//' until the end of the line.

Single line comment

Enter one or more characters that will indicate the start of a comment (ended by a new line).

Advanced...

Opens a new dialog with advanced settings. There is support for quotes, different decimal separators in floating point numbers, and character encoding. Also, for ignoring whitespaces, for allowing rows with too few data items, for making row IDs unique (not recommended for huge files), for a global missing value pattern, and for limiting the number of rows read in.

Click on the table header

If the column header in the preview table is clicked, a new dialog opens where column properties can be set: name and type can be changed (and will be fixed then). A pattern can be entered that will cause a "missing cell" to be created when it's read for this column. Additionally, possible values of the column domain can be updated by selecting "Domain". And, you can choose to skip this column entirely, i.e. it will not be included in the output table then.

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Further Links

• KNIME E-Learning Course: File Reader Nodewww.knime.com/knime-introductory-course/chapter2/section1/file-reader-node

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