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Several of the built-in expansion functions relate specifically to taking apart file names or lists of file names.
Each of the following functions performs a specific transformation on a file name. The argument of the function is regarded as a series of file names, separated by whitespace. (Leading and trailing whitespace is ignored.) Each file name in the series is transformed in the same way and the results are concatenated with single spaces between them.
$(dir names…)
Extracts the directory-part of each file name in names
. The
directory-part of the file name is everything up through (and
including) the last slash in it. If the file name contains no slash,
the directory part is the string ‘./
’. For example,
$(dir src/foo.c hacks)
produces the result ‘src/ ./
’.
$(notdir names…)
Extracts all but the directory-part of each file name in names
.
If the file name contains no slash, it is left unchanged. Otherwise,
everything through the last slash is removed from it.
A file name that ends with a slash becomes an empty string. This is unfortunate, because it means that the result does not always have the same number of whitespace-separated file names as the argument had; but we do not see any other valid alternative.
For example,
$(notdir src/foo.c hacks)
produces the result ‘foo.c hacks
’.
$(suffix names…)
Extracts the suffix of each file name in names
. If the file name
contains a period, the suffix is everything starting with the last
period. Otherwise, the suffix is the empty string. This frequently
means that the result will be empty when names
is not, and if
names
contains multiple file names, the result may contain fewer
file names.
For example,
$(suffix src/foo.c src-1.0/bar.c hacks)
produces the result ‘.c .c
’.
$(basename names…)
Extracts all but the suffix of each file name in names
. If the
file name contains a period, the basename is everything starting up to
(and not including) the last period. Periods in the directory part are
ignored. If there is no period, the basename is the entire file name.
For example,
$(basename src/foo.c src-1.0/bar hacks)
produces the result ‘src/foo src-1.0/bar hacks
’.
$(addsuffix suffix,names…)
The argument names
is regarded as a series of names, separated
by whitespace; suffix
is used as a unit. The value of
suffix
is appended to the end of each individual name and the
resulting larger names are concatenated with single spaces between
them. For example,
$(addsuffix .c,foo bar)
produces the result ‘foo.c bar.c
’.
$(addprefix prefix,names…)
The argument names
is regarded as a series of names, separated
by whitespace; prefix
is used as a unit. The value of
prefix
is prepended to the front of each individual name and the
resulting larger names are concatenated with single spaces between
them. For example,
$(addprefix src/,foo bar)
produces the result ‘src/foo src/bar
’.
$(join list1,list2)
Concatenates the two arguments word by word: the two first words (one
from each argument) concatenated form the first word of the result, the
two second words form the second word of the result, and so on. So the
n
th word of the result comes from the n
th word of each
argument. If one argument has more words that the other, the extra
words are copied unchanged into the result.
For example, ‘$(join a b,.c .o)
’ produces ‘a.c b.o
’.
Whitespace between the words in the lists is not preserved; it is replaced with a single space.
This function can merge the results of the dir
and
notdir
functions, to produce the original list of files which
was given to those two functions.
$(wildcard pattern)
The argument pattern
is a file name pattern, typically containing
wildcard characters (as in shell file name patterns). The result of
wildcard
is a space-separated list of the names of existing files
that match the pattern.
See Using Wildcard Characters in File Names.
$(realpath names…)
For each file name in names
return the canonical absolute name.
A canonical name does not contain any .
or ..
components,
nor any repeated path separators (/
) or symlinks. In case of a
failure the empty string is returned. Consult the realpath(3)
documentation for a list of possible failure causes.
$(abspath names…)
For each file name in names
return an absolute name that does
not contain any .
or ..
components, nor any repeated path
separators (/
). Note that, in contrast to realpath
function, abspath
does not resolve symlinks and does not require
the file names to refer to an existing file or directory. Use the
wildcard
function to test for existence.
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