----

<<TOC>>
----
*** Title: Regsub -all, Match Line, and Replace, Working on a Text File V2 ***

----
***Find a text in a line and replace the next line***
---
[gold]  3/26/2024.  Found example code on Ask11, seemed a useful lesson and example code on regsub and replace, if links were added to find same in the Wiki stacks.
----

tclamateur : I want to find a text in a line and replace the contents of the next line with a new string. I tried regsub, but it is only matching the first line. I don't know how to go to the next line.
eg:
[tclamateur]: I want to find a text in a line and replace the contents of the next line with a new string. I tried regsub, but it is only matching the first line. I don't know how to go to the next line.
eg:

line 5> this is line 5.

line 6> apple


with

line 5> this is line 5.

line 6> banana


Thanks

[AMG]: [[[regsub]]] has the `-all` option to replace every occurrence, not just the first.

======
proc replace {match replacement text} {
    # Backslash-quote special characters in match and replacement so they will
    # be interpreted as literal strings.
    regsub -all {[][*+?{}()<>|.^$]} $match {\\&} match
    regsub -all {[\\&]} $replacement {\\&} replacement

    # Perform the replacement.
    regsub -all ($match\\n)\[^\\n\]* $text \\1$replacement
}

replace "this is line 5." banana {
this is line 5.
apple
this is line 5.
another apple
this is not line 5.
yet more apples
}
======

This gives the following result:

======none
this is line 5.
banana
this is line 5.
banana
this is not line 5.
yet more apples
======

[MG] offers:
======
proc replace2 {args} {

if { [llength $args] < 3} {
     return -code error "wrong # arguments: replace2 ?-all? ?-regexp|-glob|-exact? \$find \$replace \$text"
   }
set find [lindex $args end-2]
set replace [lindex $args end-1]
set text [lindex $args end]
set args [lrange $args 0 end-3
]
set matchtype -exact
set all ""
foreach x $args {
if {$x eq "" } {
    continue;
   } elseif { $x eq "-all" } {
     set all [list "-all"]
   } elseif { $x in [list -regexp -glob -exact] } {
     set matchtype $x
   } else {
     return -code error "unknown option '$x'"
   }
}
set text [split $text \n]
set matches [lsearch {*}$all $matchtype $text $find]
if { [llength $matches] && [lindex $matches 0] != -1 } {
     foreach x $matches {
        incr x
        set text [lreplace $text $x $x $replace]
     }
   }
return [join $text "\n"]

}

# Example:
replace2 -all -exact "this is line 5." banana {
this is line 5.
apple
this is line 5.
another apple
this is not line 5.
yet more apples
}
======

[tclamateur]: Thanks for the input. In my case I'll have only two inputs. The input "match" and the input "replacement". What to give as input for "text"?

[AMG]: Whatever text you want the substitution to be performed on.  For instance, if you're working on a file, you'd supply the contents of that file.  
Then write the return value back out to the file, and you're done.
----
***References on Wiki***

----
'''regsub''', a [Tcl Commands%|%built-in Tcl command], performs substitutions
based on [regular expression] pattern matching.


** See Also **

   [regular expressions]:   information about Tcl regular expressions that is not unique to any particular command

   [string map]:   

   [subst]:   


** Synopsis **

    :   '''regsub''' ?''switches''? ''exp string subSpec'' ?''varName''?

----
 
**Hidden Comments Section**

<<discussion>>
Please include your wiki MONIKER and date in your comment with the same courtesy that I will give you. Thanks, [gold] 3/26/2024 
----
<<categories>> Arts and Crafts of Tcl-Tk Programming | Command | String Processing 
----
<<categories>> Numerical Analysis | Toys | Calculator | Mathematics
----
----
<<categories>> Community | Advocacy| Example| Toys and Games | Games | Application | GUI