subst(1) [debian man page]
SUBST(1) General Commands Manual SUBST(1) NAME
subst - substitute definitions into file(s) SYNOPSIS
subst [ -e editor ] -f substitutions victim ... DESCRIPTION
Subst makes substitutions into files, in a way that is suitable for customizing software to local conditions. Each victim file is altered according to the contents of the substitutions file. The substitutions file contains one line per substitution. A line consists of two fields separated by one or more tabs. The first field is the name of the substitution, the second is the value. Neither should contain the character `#', and use of text-editor metacharacters like `&' and `' is also unwise; the name in particular is best restricted to be alphanumeric. A line starting with `#' is a comment and is ignored. In the victims, each line on which a substitution is to be made (a target line) must be preceded by a prototype line. The prototype line should be delimited in such a way that it will be taken as a comment by whatever program processes the file later. The prototype line must contain a ``prototype'' of the target line bracketed by `=()<' and `>()='; everything else on the prototype line is ignored. Subst extracts the prototype, changes all instances of substitution names bracketed by `@<' and `>@' to their values, and then replaces the tar- get line with the result. OPTIONS
-e Substitutions are done using the sed(1) editor, which must be found in either the /bin or /usr/bin directories. To specify a dif- ferent executable, use the ``-e'' flag. EXAMPLE
If the substitutions file is FIRST 111 SECOND 222 and the victim file is x = 2; /* =()<y = @<FIRST>@ + @<SECOND>@;>()= */ y = 88 + 99; z = 5; then ``subst -f substitutions victim'' changes victim to: x = 2; /* =()<y = @<FIRST>@ + @<SECOND>@;>()= */ y = 111 + 222; z = 5; FILES
victimdir/substtmp.new new version being built victimdir/substtmp.old old version during renaming SEE ALSO
sed(1) DIAGNOSTICS
Complains and halts if it is unable to create its temporary files or if they already exist. HISTORY
Written at U of Toronto by Henry Spencer. Rich $alz added the ``-e'' flag July, 1991. BUGS
When creating a file to be substed, it's easy to forget to insert a dummy target line after a prototype line; if you forget, subst ends up deleting whichever line did in fact follow the prototype line. 25 Feb 1990 SUBST(1)
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subst(n) Tcl Built-In Commands subst(n) __________________________________________________________________________________________________________________________________________________ NAME
subst - Perform backslash, command, and variable substitutions SYNOPSIS
subst ?-nobackslashes? ?-nocommands? ?-novariables? string _________________________________________________________________ DESCRIPTION
This command performs variable substitutions, command substitutions, and backslash substitutions on its string argument and returns the fully-substituted result. The substitutions are performed in exactly the same way as for Tcl commands. As a result, the string argument is actually substituted twice, once by the Tcl parser in the usual fashion for Tcl commands, and again by the subst command. 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 speci- fied, 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 substi- tution, the result of the whole substitution will be the string (as substituted) up to the start of the substitution that raised the excep- tion. 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
When it performs its substitutions, subst does not give any special treatment to double quotes or curly braces (except within command sub- stitutions) so the script set a 44 subst {xyz {$a}} returns "xyz {44}", not "xyz {$a}" and the script set a "p} q {r" subst {xyz {$a}} returns "xyz {p} q {r}", not "xyz {p} q {r}". When command substitution is performed, it includes any variable substitution necessary to evaluate the script. set a 44 subst -novariables {$a [format $a]} returns "$a 44", not "$a $a". Similarly, when variable substitution is performed, it includes any command substitution necessary to retrieve the value of the variable. proc b {} {return c} array set a {c c [b] tricky} subst -nocommands {[b] $a([b])} returns "[b] c", not "[b] tricky". 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} returns "abc,", not "abc,,def" and the script subst {abc,[continue;expr {1+2}],def} returns "abc,,def", not "abc,3,def". Other exceptional return codes substitute the returned value subst {abc,[return foo;expr {1+2}],def} returns "abc,foo,def", not "abc,3,def" and subst {abc,[return -code 10 foo;expr {1+2}],def} also returns "abc,foo,def", not "abc,3,def". SEE ALSO
Tcl(n), eval(n), break(n), continue(n) KEYWORDS
backslash substitution, command substitution, variable substitution Tcl 7.4 subst(n)