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Macros start with a dollar sign, like shellvariables. Our first <TT>`Makefile'</TT> used a few:</P><P><TABLE><tr><td> </td><td class=smallexample><FONT SIZE=-1><pre>$(CC) $(CFLAGS) -c $< -o $@</FONT></pre></td></tr></table></P><P>Here, syntactic forms of <SAMP>`$(..)'</SAMP> are <CODE>make</CODE> variableexpansions. It is possible to define a <CODE>make</CODE> variable using a<SAMP>`<VAR>var</VAR>=<VAR>value</VAR>'</SAMP> syntax:</P><P><TABLE width=100%><tr><td> </td><td class=example bgcolor=#6688aa><br><pre>CC = ec++</pre></td></tr></table></P><P>In a <TT>`Makefile'</TT>, <CODE>$(CC)</CODE> will then be literally replaced by<SAMP>`ec++'</SAMP>. <CODE>make</CODE> has a number of built-in variables anddefault values. The default value for <SAMP>`$(CC)'</SAMP> is <STRONG>cc</STRONG>.</P><P>Other built-in macros exist with fixed semantics. The two most commonmacros are <CODE>$@</CODE> and <CODE>$<</CODE>. They represent the names of thetarget and the first dependency for the rule in which they appear.<CODE>$@</CODE> is available in any rule, but for some versions of<CODE>make</CODE> <CODE>$<</CODE> is only available in suffix rules. Here is asimple <TT>`Makefile'</TT>:</P><P><TABLE width=100%><tr><td> </td><td class=example bgcolor=#6688aa><br><pre>all: dummy @echo "$@ depends on dummy"dummy: touch $@</pre></td></tr></table></P><P>This is what <CODE>make</CODE> outputs when processing this<TT>`Makefile'</TT>:</P><P><TABLE width=100%><tr><td> </td><td class=example bgcolor=#6688aa><br><pre>$ maketouch dummyall depends on dummy</pre></td></tr></table></P><P>The GNU Make manual documents these macros in more detail.</P><P><A NAME="Suffix rules"></A></TR></TABLE><BR> <FONT SIZE="-1">This document was generatedby <I>Gary V. Vaughan</I> on <I>September, 12 2004</I>using <A HREF="http://www.mathematik.uni-kl.de/~obachman/Texi2html"><I>texi2html</I></A></BODY></HTML>⌨️ 快捷键说明
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