Roland Ver. 4.5 Technické informace stáhnout pdf (Strana 94)

84 GNU make

8.2 Functions for String Substitution and Analysis

Here are some functions that operate on strings:

$(subst from,to,text)

Performs a textual replacement on the text text: each occurrence of from is

replaced by to. The result is substituted for the function call. For example,

$(subst ee,EE,feet on the street)

substitutes the string ‘fEEt on the strEEt’.

$(patsubst pattern,replacement,text)

Finds whitespace-separated words in text that match pattern and replaces them

with replacement. Here pattern may contain a ‘%’ which acts as a wildcard,

matching any number of any characters within a word. If replacement also con-

tains a ‘%’, the ‘%’ is replaced by the text that matched the ‘%’ in pattern. Only

the ﬁrst ‘%’ in the pattern and replacement is treated this way; any subsequent

‘%’ is unchanged.

‘%’ characters in patsubst function invocations 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 ﬁle names or

has a stem substituted into it. Backslashes that are not in danger of quoting ‘%’

characters go unmolested. For example, the pattern the\%weird\\%pattern\\

has ‘the%weird\’ preceding the operative ‘%’ character, and ‘pattern\\’ fol-

lowing it. The ﬁnal two backslashes are left alone because they cannot aﬀect

any ‘%’ character.

Whitespace between words is folded into single space characters; leading and

trailing whitespace is discarded.

For example,

$(patsubst %.c,%.o,x.c.c bar.c)

produces the value ‘x.c.o bar.o’.

Substitution references (see Section 6.3.1 [Substitution References], page 62)

are a simpler way to get the eﬀect of the patsubst function:

$(var:pattern=replacement)

is equivalent to

$(patsubst pattern,replacement,$(var))

The second shorthand simpliﬁes one of the most common uses of patsubst:

replacing the suﬃx at the end of ﬁle names.

$(var:suffix=replacement)

is equivalent to

$(patsubst %suffix,%replacement,$(var))

For example, you might have a list of object ﬁles:

objects = foo.o bar.o baz.o

To get the list of corresponding source ﬁles, you could simply write:

1 2 ... 89 90 91 92 93 94 95 96 97 98 99 ... 211 212

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Roland Ver. 4.5 Technické informace Strana 94