Practical Programming in Tcl & Tk, Third Edition

Input/Output Command Summary

The following sections describe how to open, read, and write files. The basic model is that you open a file, read or write it, then close the file. Network sockets also use the commands described here. Socket programming is discussed in Chapter 17, and more advanced event-driven I/O is described in Chapter 16. Table 9-5 lists the basic commands associated with file I/O:

Table 9-5. Tcl commands used for file access.

open what ?access? ?permissions?	Returns channel ID for a file or pipeline.
puts ?-nonewline? ?channel? string	Writes a string.
gets channel ?varname?	Reads a line.
read channel ?numBytes?	Reads numBytes bytes, or all data.
read -nonewline channel	Reads all bytes and discard the last \n.
tell channel	Returns the seek ...