wildcard character

A wildcard character is a symbol or a special character that is used to represent one or more characters in a text string. The most common wildcard characters are the asterisk (*) and the question mark (?). The asterisk represents any number of characters, while the question mark represents a single character. These characters are commonly used in computer programming, data processing, and file searching to match patterns of text or to substitute for unknown or variable characters.

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wildcard in makefile

In Makefiles, a wildcard is a character or sequence of characters that represents one or more other characters. It is often used to match file names or patterns.

The most common use of wildcards in Makefiles is with the "wildcard" function. The syntax of the "wildcard" function is as follows:

$(wildcard pattern)

This function expands to a space-separated list of all the file names that match the given pattern. For example, to get a list of all the C source files in the current directory, you could use:

C_FILES := $(wildcard *.c)

This would set the variable "C_FILES" to a space-separated list of all the files in the current directory that end with ".c".

Another way to use wildcards in Makefiles is with pattern rules. Pattern rules are used to define a rule for building a set of files that match a particular pattern. For example:

%.o: %.c
    $(CC) $(CFLAGS) -c $< -o $@

This rule tells Make to build any file with the ".o" extension that corresponds to a file with the ".c" extension. The "$<" and "$@" variables are used to represent the input and output files, respectively.

Overall, wildcards are a powerful feature of Makefiles that allow you to write more generic rules and automate your build process.

is the usage of wildcard and firstword in makefile?

In a Makefile, a wildcard is a special character that matches any number of characters in a filename. The `wildcard` function can be used to find all files that match a particular pattern. For example, the following line will find all files in the current directory that end with ".c":

SOURCES := $(wildcard *.c)

The `firstword` function, on the other hand, is used to extract the first word from a string. This is often used in Makefiles to extract the first word from a list of space-separated values. For example, the following line extracts the first word from the `SOURCES` variable defined above:

FIRST_SOURCE := $(firstword $(SOURCES))

This would set the `FIRST_SOURCE` variable to the name of the first C file in the current directory.