tcl find and replace in file - replace

Question

I need help with tcl. I have a text file with the following format:
Main = 1
Bgp = 0
Backup = 1
I need to increment the integer value by 1 for each item, for example replacing Main = 1 with Main = 2, and so on.

Answer 1

Another approach:
# read the data
set f [open file]
set data [read -nonewline $f]
close $f
# increment the numbers
regsub -all {=\s*(\d+)\s*$} $data {= [expr {\1 + 1}]} new
set new [subst -novariables -nobacklashes $new]
# write the data
set f [open file w]
puts $f $new
close $f
That regsub command will replace Main = 1 with Main = [expr {1 + 1}], and then the subst command actually invokes the expr command to compute the new value

Answer 2

(Changed my answer: I was a little irritable, sorry.)
If the text to be processed is in a variable called data, one can turn the text into a list of words and go through them three at a time like this:
set result ""
foreach {keyword op value} [split [string trim $data]] {
append result "$keyword $op [incr value]\n"
}
In this case, each keyword (Main, Bgp, Backup, ...) ends up inside the loop variable keyword, each equals sign (or whatever is in the second position) ends up inside the loop variable op, and each value to be incremented ends up inside value.
(When splitting, it's typically a good idea to trim off white-space at the beginning and end of the text first: otherwise one can get empty "ghost" elements. Hence: split [string trim $data])
We can read the data from the file "datafile" like this:
set f [open datafile r+]
set data [read $f]
Note that we use r+ to be able to both read from and write to the file.
Once we have processed the data, we can write it back at the beginning of the file like this:
seek $f 0
puts -nonewline $f $result
close $f
or possibly like this, which means we didn't have to open the file with r+:
close $f
set f [open datafile w]
puts -nonewline $f $result
close $f
Putting it together:
set f [open datafile r+]
set data [read $f]
set result ""
foreach {keyword op value} [split [string trim $data]] {
append result "$keyword $op [incr value]\n"
}
seek $f 0
puts -nonewline $f $result
close $f
This procedure can also be simplified a bit using the standard package fileutil, which can take care of the file opening, closing, reading, and writing for us.
First, we put the processing in a procedure:
proc process data {
foreach {keyword = value} [split [string trim $data]] {
append result "$keyword ${=} [incr value]\n"
}
return $result
}
Then we can just ask ask updateInPlace to update the contents of the file with new contents processed by process.
package require fileutil
::fileutil::updateInPlace datafile process
And that's it.
Documentation:
append,
close,
fileutil (package),
foreach,
incr,
open,
package,
proc,
puts,
read,
return,
seek,
set,
split,
string