Tcl: Multiple Conditionals Inside the If Statement

Question

Just trying to do some basic check in a script... to produce an error if $argc is not either 1 or 2.

I tried:

if { ( $argc != 1 ) || ( $argc != 2 ) } {
        puts "ERROR: \$argc should be either 1 or 2.\n"; exit 1
}

and

if { ( $argc != 1 || $argc != 2 ) } {
        puts "ERROR: \$argc should be either 1 or 2.\n"; exit 1
}

etc.

but couldn't make it work using any of the parenthesis/brace combinations.

Any help would be greatly appreciated.

Accepted Answer

This is basic logic.

Your example won't work because 2 is not equal to 1 so the first test is true.

To negate an OR conjunction, you negate each test and change the OR to an AND. You want this state:

if { ( $argc == 1 ) || ( $argc == 2 ) } {
  puts "ok"
} else {
  puts "ng"
}

So use:

if { ( $argc != 1 ) && ( $argc != 2 ) } {
  # i.e. if $argc is either anything other than a 1 or a 2...
  puts "ERROR: \$argc should be either 1 or 2.\n"; exit 1
}

Answer 2

Another way:

if {$argc ni {1 2}} { ... }

That is: if the value of argc is not in the list containing 1 and 2, ...

The ni operator requires Tcl 8.5 or later.

Documentation: if, ni (operator)

Tcl: Multiple Conditionals Inside the If Statement

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Tcl: Multiple Conditionals Inside the If Statement

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David Miller