4.5.2 The vpath Directive
Similar to the VPATH variable, but more selective, is the
vpath 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 directive:
vpath pattern directories
- Specify the search path directories for file names that match
pattern.
The search path, directories, is a list of directories to be
searched, separated by colons (semi-colons on MS-DOS and MS-Windows) or
blanks, just like the search path used in the VPATH variable.
vpath pattern
- Clear out the search path associated with pattern.
vpath
Clear all search paths previously specified with vpath directives.
A vpath pattern is a string containing a `%' character. The
string must match the file name of a prerequisite 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
end in .h. (If there is no `%', the pattern must match the
prerequisite 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 prerequisite fails to exist in the current directory, if the
pattern in a vpath directive matches the name of the
prerequisite file, then the directories in that directive are searched
just like (and before) the directories in the VPATH variable.
For example,
tells make to look for any prerequisite whose name ends in `.h'
in the directory `../headers' if the file is not found in the current
directory.
If several vpath patterns match the prerequisite file's name, then
make processes each matching vpath directive one by one,
searching all the directories mentioned in each directive. make
handles multiple vpath directives in the order in which they
appear in the makefile; multiple directives with the same pattern are
independent of each other.
Thus,
| | 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'.
