NAME

SYNOPSIS

DESCRIPTION

If any of the -nobackslashes, -nocommands, or -novariables are specified, then the corresponding substitutions are not performed. For example, if -nocommands is specified, command substitution is not performed: open and close brackets are treated as ordinary characters with no special interpretation.

Note that the substitution of one kind can include substitution of other kinds. For example, even when the -novariables option is specified, command substitution is performed without restriction. This means that any variable substitution necessary to complete the command substitution will still take place. Likewise, any command substitution necessary to complete a variable substitution will take place, even when -nocommands is specified. See the EXAMPLES below.

If an error occurs during substitution, then subst will return that error. If a break exception occurs during command or variable substitution, the result of the whole substitution will be the string (as substituted) up to the start of the substitution that raised the exception. If a continue exception occurs during the evaluation of a command or variable substitution, an empty string will be substituted for that entire command or variable substitution (as long as it is well-formed Tcl.) If a return exception occurs, or any other return code is returned during command or variable substitution, then the returned value is substituted for that substitution. See the EXAMPLES below. In this way, all exceptional return codes are “caught” by subst. The subst command itself will either return an error, or will complete successfully.

EXAMPLES

set a 44
subst {xyz {$a}}

set a "p\} q \{r"
subst {xyz {$a}}

When command substitution is performed, it includes any variable substitution necessary to evaluate the script.

set a 44
subst -novariables {$a [format $a]}

proc b {} {return c}
array set a {c c [b] tricky}
subst -nocommands {[b] $a([b])}

The continue and break exceptions allow command substitutions to prevent substitution of the rest of the command substitution and the rest of string respectively, giving script authors more options when processing text using subst. For example, the script

subst {abc,[break],def}

subst {abc,[continue;expr {1+2}],def}

Other exceptional return codes substitute the returned value

subst {abc,[return foo;expr {1+2}],def}

subst {abc,[return -code 10 foo;expr {1+2}],def}

SEE ALSO

KEYWORDS