Functions for File Names

Functions for File Names

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.

$(word n,text)

Returns the nth word of text. The legitimate values of n start from 1. If n is bigger than the number of words in text, the value is empty. For example,

$(word 2, foo bar baz)

returns `bar’.

$(wordlist s,e,text)

Returns the list of words in text starting with word s and ending with word e (inclusive). The legitimate values of s and e start from 1. If s is bigger than the number of words in text, the value is empty. If e is bigger than the number of words in text, words up to the end of text are returned. If s is greater than e, make swaps them for you. For example,

$(wordlist 2, 3, foo bar baz)

returns `bar baz’.

$(words text)

Returns the number of words in text. Thus, the last word of text is $(word $(words text),text).

$(firstword names...)

The argument names is regarded as a series of names, separated by whitespace. The value is the first name in the series. The rest of the names are ignored. For example,

$(firstword foo bar)

produces the result `foo’. Although $(firstword text) is the same as $(word 1,text), the firstword function is retained for its simplicity.

$(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 section Using Wildcard Characters in File Names.

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