Subst performs a substitution pass without performing any execution of commands except those required for the substitution to occur, ie: commands within [] will be executed, and the results placed in the return string.
In the example code:
puts "[subst $$c]\n"shows an example of placing a variable name in a variable, and evaluating through the indirection.
The format command can also be used to force some levels of substitution to occur.
If any of the -no... arguments are present, then that set of substitutions will not be done.
NOTE: subst does not honor braces or quotes.
set a "alpha" set b a puts {a and b with no substitution: $a $$b} puts "a and b with one pass of substitution: $a $$b" puts "a and b with subst in braces: [subst {$a $$b}]" puts "a and b with subst in quotes: [subst "$a $$b"]\n" puts "format with no subst [format {$%s} $b]" puts "format with subst: [subst [format {$%s} $b]]" eval "puts \"eval after format: [format {$%s} $b]\"" set num 0; set cmd "proc tempFileName {} " set cmd [format "%s {global num; incr num;" $cmd] set cmd [format {%s return "/tmp/TMP.%s.$num"} $cmd [pid] ] set cmd [format "%s }" $cmd ] eval $cmd puts "[info body tempFileName]" set a arrayname set b index set c newvalue eval [format "set %s(%s) %s" $a $b $c] puts "Index: $b of $a was set to: $arrayname(index)"