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Chapter 8: Functions for Transforming Text 89

$(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 4.3 [Using Wildcard Characters in File Names], page 23.

$(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 separa-

tors (/) 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.

8.4 Functions for Conditionals

There are three functions that provide conditional expansion. A key aspect of these func-

tions is that not all of the arguments are expanded initially. Only those arguments which

need to be expanded, will be expanded.

$(if condition,then-part[,else-part])

The if function provides support for conditional expansion in a functional

context (as opposed to the GNU make makeﬁle conditionals such as ifeq (see

Section 7.2 [Syntax of Conditionals], page 78).

The ﬁrst argument, condition, ﬁrst has all preceding and trailing whitespace

stripped, then is expanded. If it expands to any non-empty string, then the con-

dition is considered to be true. If it expands to an empty string, the condition

is considered to be false.

If the condition is true then the second argument, then-part, is evaluated and

this is used as the result of the evaluation of the entire if function.

If the condition is false then the third argument, else-part, is evaluated and this

is the result of the if function. If there is no third argument, the if function

evaluates to nothing (the empty string).

Note that only one of the then-part or the else-part will be evaluated, never

both. Thus, either can contain side-eﬀects (such as shell function calls, etc.)

$(or condition1[,condition2[,condition3...]])

The or function provides a “short-circuiting” OR operation. Each argument

is expanded, in order. If an argument expands to a non-empty string the

processing stops and the result of the expansion is that string. If, after all

arguments are expanded, all of them are false (empty), then the result of the

expansion is the empty string.

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Roland Ver. 4.5 Technical Information Seite 99