(make.info.gz) File Name Functions
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8.3 Functions for File Names
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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 Nth word of the result comes from the Nth 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. Using Wildcard Characters in
File Names Wildcards.
`$(realpath NAMES...)'
For each file name in NAMES return the canonical absolute name. A
canonical name does not contain any `.' or `..' components, nor
any repeated path separators (`/') or symlinks. In case of a
failure the empty string is returned. Consult the `realpath(3)'
documentation for a list of possible failure causes.
`$(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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