Similar to the
VPATH variable but more selective is the
directive (note lower case), which allows you to specify a search path for a particular class
of file names, those that match a particular pattern. Thus you can supply
certain search directories for one class of file names and other directories
(or none) for other file names.
There are three forms of the
vpath pattern directories
vpath pattern is a string containing a `%' character. The
string must match the file name of a dependency that is being searched
for, the `%' character matching any sequence of zero or more
characters (as in pattern rules; see section Defining and Redefining Pattern Rules). For example,
%.h matches files that
.h. (If there is no `%', the pattern must match the
dependency exactly, which is not useful very often.)
`%' characters in a
vpath directive's pattern can be quoted
with preceding backslashes (`\'). Backslashes that would otherwise
quote `%' characters can be quoted with more backslashes.
Backslashes that quote `%' characters or other backslashes are
removed from the pattern before it is compared to file names. Backslashes
that are not in danger of quoting `%' characters go unmolested.
When a dependency fails to exist in the current directory, if the
pattern in a
vpath directive matches the name of the
dependency file, then the directories in that directive are searched
just like (and before) the directories in the
vpath %.h ../headers
make to look for any dependency whose name ends in `.h'
in the directory `../headers' if the file is not found in the current
vpath patterns match the dependency file's name, then
make processes each matching
vpath directive one by one,
searching all the directories mentioned in each directive.
vpath directives in the order in which they
appear in the makefile; multiple directives with the same pattern are
independent of each other.
vpath %.c foo vpath % blish vpath %.c bar
will look for a file ending in `.c' in `foo', then `blish', then `bar', while
vpath %.c foo:bar vpath % blish
will look for a file ending in `.c' in `foo', then `bar', then `blish'.
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