---
name: "if"
section: "3tcl"
platform: "linux"
package: "tcl8.6-doc"
version: "8.6.16+dfsg-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/if/3tcl"
---

# if(3tcl)

Execute scripts conditionally

```

```

## NAME

if - Execute scripts conditionally

## SYNOPSIS

**if** *expr1* ?**then**? *body1* **elseif** *expr2* ?**then**? *body2* **elseif** ... ?**else**? ?*bodyN*?

```

```

## DESCRIPTION

The *if* command evaluates *expr1* as an expression (in the same way that **expr** evaluates its argument).  The value of the expression must be a boolean (a numeric value, where 0 is false and anything is true, or a string value such as **true** or **yes** for true and **false** or **no** for false); if it is true then *body1* is executed by passing it to the Tcl interpreter. Otherwise *expr2* is evaluated as an expression and if it is true then **body2** is executed, and so on. If none of the expressions evaluates to true then *bodyN* is executed. The **then** and **else** arguments are optional “noise words” to make the command easier to read. There may be any number of **elseif** clauses, including zero. *BodyN* may also be omitted as long as **else** is omitted too. The return value from the command is the result of the body script that was executed, or an empty string if none of the expressions was non-zero and there was no *bodyN*.

## EXAMPLES

A simple conditional:

```
if {$vbl == 1} { puts "vbl is one" }
```

With an **else**-clause:

```
if {$vbl == 1} {
    puts "vbl is one"
} else {
    puts "vbl is not one"
}
```

With an **elseif**-clause too:

```
if {$vbl == 1} {
    puts "vbl is one"
} elseif {$vbl == 2} {
    puts "vbl is two"
} else {
    puts "vbl is not one or two"
}
```

Remember, expressions can be multi-line, but in that case it can be a good idea to use the optional **then** keyword for clarity:

```
if {
    $vbl == 1
    || $vbl == 2
    || $vbl == 3
} then {
    puts "vbl is one, two or three"
}
```

## SEE ALSO

[expr(3tcl)](/expr/3tcl.md), [for(3tcl)](/for/3tcl.md), [foreach(3tcl)](/foreach/3tcl.md)

## KEYWORDS

boolean, conditional, else, false, if, true