gold Note to clean up crew. Checking end of line issues here from laptop PC editor. If one sees a syntax error or brace typo error, go ahead and change. My eyes are bad on these tiny fonts.
gold 3/26/2024. Found example code for regsub on Ask, and it shall be given # 11. Seemed a useful lesson and example code on regsub and replace, if category links and Wiki page references 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:
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.
The regsub command in Tcl (Tool Control Language) performs substitutions based on regular expression pattern matching. Let’s dive into its usage and provide some examples:
Basic Syntax:
regsub ?switches? exp string subSpec ?varName?
exp: The regular expression pattern.
string: The input string to match against.
subSpec: The substitution specification.
varName (optional): If provided, the resulting string is stored in this variable, and the number of substitutions is returned. Switches:
-all: Causes regsub to perform the replacement in as many non-overlapping places as possible.
Other switches (e.g., -nocase, -start index) are similar to those for regexp.
Examples: a. Replace a specific substring in a file name:
set filename "file.c"
regsub -- {([^\\.]+)\\.c} $filename {cc -c & -o \\1.o}
# Result: "cc -c file.c -o file.o"b. Convert a string template:
set input "rand ||=> this is some text <=|| rand"
set unique1 {\\|\\|=>}
set unique2 {<=\\|\\|}
set replacement {some other text}
set new [regsub -- "($unique1).*($unique2)" $input "\\1$replacement\\2"]
puts $new
# Result: "rand ||=> some other text <=|| rand"c. Custom substitution using -command:
set string "ab-cd-ef-gh"
regsub -all -command {w} $string {puts}
# Prints the letters 'a' to 'h', one per line.d. More advanced example using -command:
set input "1234A000aadA12234"
set substring "BX"
regsub -all -command {(A[^A]*A)} $input {[string repeat $substring [expr {[string length "\\1"] / [string length $substring]}]]} new_string
puts $new_string
# Result: "1234BXBXBXBX12234"Remember that regsub is a powerful tool for manipulating strings using regular expressions. Feel free to experiment and adapt it to your specific needs! For more details, one can refer to the official Tcl documentation core.
regsub, a built-in Tcl command, performs substitutions based on regular expression pattern matching.
Please include your wiki MONIKER and date in your comment with the same courtesy that I will give you. Thanks, gold 3/26/2024
gold 3/27/2024. Note to clean up crew. Checking end of line issues here from laptop PC editor. If one sees a syntax error or brace typo error, go ahead and change. My eyes are bad on these tiny fonts.
| Arts and Crafts of Tcl-Tk Programming | Category Command | Category String Processing | Category Discussion | Category Development |