Reading a file

Reading a file allows us to retrieve the stored data from the open channel. To accomplish this Tcl provides the read command. The command utilizes two forms. The syntax is as follows:

read -nonewline channel
read channel number

How to do it…

Enter the following command:

% set fp [open text.txt r]
file5
% read $fp
Hello World

How it works…

In the first form, the read command reads all the data from the channel. If the optional nonewline switch is provided then the last character of the file is discarded if it is a newline. In the second form, the number argument instructs the command to return the number of characters specified unless there are fewer characters in the file in which case all characters will be returned.

By using the read command we accessed the channel and the data read from the file was displayed. As referenced in the previous tables detailing access permissions, the channel can be set to non-blocking with the optional NONBLOCK POSIX keyword. If the channel is...