SUBST(1)SUBST(1)NAMEsubst - substitute definitions into file(s)SYNOPSISsubst [ -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 con‐
sists 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 tar‐
get 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.
Substitutions are done using the sed(1) editor, which must be found in
either the /bin or /usr/bin directories. To specify a different exe‐
cutable, 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 ALSOsed(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.
local SUBST(1)
