File handling

Now that we can open, read, write, and close a file, it is time to put this knowledge to work in a real world manner. We will now create a Tcl script that accesses a file, reorders the stored data, and then outputs it to a secondary file. This is similar to a file handling procedure used to clean up user supplied files.

Getting ready

Using the text editor of your choice create a text file containing the following text:

1,3,5,7,8,2,4,6,9

Save the file in your working directory as input.txt.

How to do it…

Using the text editor of your choice create the following Tcl script and save it in your working directory as filehandler.tcl.

# Check that a filename was provided
if { $argc>0 & $argv>0} {
# Assign the filename to a variable
set fname [lindex $argv 0]
# Open the file for read-only access
set fp [open $fname r]
# Read the contents of the file into a variable
set data [read $fp]
#Close the input file
close $fp
# Split the data and create a Tcl list
set input [split $data...