下表列出了所有Tcl语言支持的关系运算符。假设变量A=10，变量B=20，则：
| 操作符 | 描述 | 例子 |
|---|---|---|
| == | 检查两个操作数的值是否相等，如果是的话那么条件为真。 | (A == B) 不为 true. |
| != | 检查两个操作数的值是否相等，如果值不相等，则条件变为真。 | (A != B) 为 true. |
| > | 检查左边的操作数的值是否大于右操作数的值，如果是的话那么条件为真。 | (A > B) 不为 true. |
| < | 检查左边的操作数的值是否小于右操作数的值，如果是的话那么条件为真。 | (A < B) 为 true. |
| >= | 如果左操作数的值大于或等于右操作数的值，如果是的话那么条件检查为真 | (A >= B) 不为 true. |
| <= | 检查左边的操作数的值是否小于或等于右操作数的值，如果是的话那么条件为真。 | (A <= B) 为 true. |
试试下面的例子就明白了所有的Tcl语言版本的关系运算符：
#!/usr/bin/tclsh
set a 21
set b 10
if { $a == $b } {
puts "Line 1 - a is equal to b\n"
} else {
puts "Line 1 - a is not equal to b\n"
}
if { $a < $b } {
puts "Line 2 - a is less than b\n"
} else {
puts "Line 2 - a is not less than b\n"
}
if { $a > $b } {
puts "Line 3 - a is greater than b\n"
} else {
puts "Line 3 - a is not greater than b\n"
}
# Lets change value of a and b
set a 5
set b 20
if { $a <= $b } {
puts "Line 4 - a is either less than or equal to b\n"
}
if { $b >= $a } {
puts "Line 5 - b is either greater than or equal to b\n"
}
当编译和执行上面的程序，会产生以下结果：
Line 1 - a is not equal to b Line 2 - a is not less than b Line 3 - a is greater than b Line 4 - a is either less than or equal to -b Line 5 - b is either greater than or equal to a
