CODEWITHSUNDEEP
tcl
Rajeshwar
Rajeshwar

Reputation: 11651

How to check if a variable is empty in tcl

How do you ceck if a variable is empty ? It could contain a "\n" or spaces. I am currently doing this

if {{string trimleft $var} != ""} {
   # the variable is not empty
   puts $var
 }

However the variable printed still seems to be empty ? will trimleft remove "\n" ? Is there a better approach to check if a string is empty ?

Upvotes: 11

Views: 58139

Answers (3)

Earnie
Earnie

Reputation: 111

To answer the original question with a concern of checking for an empty line here is the corrected code example:

if {[string trim $var] != ""} {
    puts $var
}

Without specifying the ?chars? the trim will remove white space chars which are considered to be space, tab, newline and carriage return.

Upvotes: 5

Bharathi
Bharathi

Reputation: 42

if {{string trimleft "\n"} eq ""} {
    puts "1"
} elseif {"\n" eq ""} {
    puts "2"
}
  • The above script will give output as nothing.
  • I think trimleft won't remove \n from the value.

Upvotes: 1

DazedAndConfused
DazedAndConfused

Reputation: 141

As far as I know, checking if a string is empty is simply done by:

if {$myString eq ""} {

    puts "string is empty"

}

Running the following should not print anything:

if {" " eq ""} {
    puts "1"
} elseif {"\n" eq ""} {
    puts "2"
}

I hope I understood your question correctly

Upvotes: 10

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