Description - Mks.com

is true if the given string is non-empty,
string == string
is true if the two strings are equal, and
string != string
is true if the two strings are not equal.
Typically, one or both strings contain macros that make expands before comparing. make also
discards white space at the start and end of the text portion before the comparison. This means
that a macro that expands to nothing but white space is considered an empty value for the purpose
of the comparison. If a macro expression needs to be compared to an empty string, compare it to
the value of the macro NULL for readability.
The text enclosed in the conditional construct must have the same format that it would have
outside the conditional. In particular, make assumes that anything that starts with a tab inside the
conditional is a recipe line. This means that you cannot use tabs to indent text inside the
conditional (except, of course, for recipe lines that always begin with tabs).
Functions
make supports the following function:
$(shell shell_cmd)
performs the same function that backquotes (`shell_cmd`) do in most shells. That is, it
performs command substitution, returning the output of the specified shell command,
shell_cmd and subsituting it into the surrounding text, after first replacing each newline or
carrige-return/newline pair with a single space and removing any trailing newline or carriagereturn/newline
pair.
The command specified with the shell function is run when the the function call is
expanded. Because this function involves spawning a new shell, you should carefully
consider the performance implications of using the shell function within recursively
expanded variables as opposed to simply expanded variables.
Software Configuration Management Integration
make provides integration with a variety of Software Configuration Management (SCM)
applications.
The SCM environment variable determines not only if SCM integration is enabled, but also which
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