Sed : Add a line at the starting of each TCL proc - sed

Question

I have a TCL proc like this, & want to add a line after the start of the proc, the puts "puts " entered myproc" " line
proc myproc { {filename "input.txt"}
{var1 "x"}
{var2 "y"}
{var3 "z"}
{var4 ""}
{var5 "0"}
{var6 "0"}
{var7 0}
} {
puts " entered myproc"
Can you help?
& it should also work for
proc myproc2 { N val } {
puts " entered myproc"
# comment line
set ret {} for { set i 0 } { $i < $N } { incr i } { lappend ret $val }
return $ret
}

Answer 1

If all you want to do is get an execution trace of your code, such as a call stack dump etc, then you don't need to modify your source code at all. You can use tcl itself to do it for you.
Tcl has no reserved keywords, none at all. Not even proc is reserved. You can therefore redefine it:
rename proc _proc
# Now proc no longer exists but we have _proc instead.
# Use it to redefine "proc":
_proc proc {name arguments body} {
set body "puts \"entered $name\";$body"
_proc $name $arguments $body
}
Just do that before running any of your own code and you'll find that every proc prints out when it's being entered on each call.
This is how a lot of tcl debuggers and profilers work - using tcl to redifine itself.
From your comments it looks like you're trying to also print how deep the stack is with each call. To do that you need to add more code to each proc definition. The most straightforward way is of course something like this:
_proc proc {name arguments body} {
set preamble"set dist2top \[info level\];puts \"\$dist2top entered $name\""
set body "$preamble;$body"
_proc $name $arguments $body
}
But as you can see, writing code inside strings can quickly become unmanagable. There are several tricks you can use to make it more manageable. One of the more common is to split $body by line and use list commands to manipulate code. It should reduce at least one level of quoting hell. My favorite is to use a templating technique similar to how you'd write html templates in MVC frameworks. I usually use string map for this:
_proc proc {name arguments body} {
_proc $name $arguments [string map [list %NAME% $name %BODY% $body] {
set dist2top [info level]
puts "$dist2top entered: %NAME%"
%BODY%
}]
}
The last argument in the _proc definition is just a string but it looks like a code block which makes it easier to read. No nasty quoting hell with this technique.

Answer 2

Using awk you can do:
awk '/^ *proc/ {$0 = $0 "\nputs \" entered myproc\""} 1' RS= proc-file.tcl
Gives this file:
proc myproc { {filename "input.txt"}
{var1 "x"}
{var2 "y"}
{var3 "z"}
{var4 ""}
{var5 "0"}
{var6 "0"}
{var7 0}
} {
puts " entered myproc"