Module Name: src
Committed By: christos
Date: Wed Jun 9 16:58:23 UTC 2010
Modified Files:
src/usr.bin/make: make.1
Log Message:
Explain variable expansion better. Requested by Aleksey Cheusov
To generate a diff of this commit:
cvs rdiff -u -r1.174 -r1.175 src/usr.bin/make/make.1
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/usr.bin/make/make.1
diff -u src/usr.bin/make/make.1:1.174 src/usr.bin/make/make.1:1.175
--- src/usr.bin/make/make.1:1.174 Sun Jun 6 13:28:48 2010
+++ src/usr.bin/make/make.1 Wed Jun 9 12:58:22 2010
@@ -1,4 +1,4 @@
-.\" $NetBSD: make.1,v 1.174 2010/06/06 17:28:48 wiz Exp $
+.\" $NetBSD: make.1,v 1.175 2010/06/09 16:58:22 christos Exp $
.\"
.\" Copyright (c) 1990, 1993
.\" The Regents of the University of California. All rights reserved.
@@ -29,7 +29,7 @@
.\"
.\" from: @(#)make.1 8.4 (Berkeley) 3/19/94
.\"
-.Dd June 6, 2010
+.Dd June 9, 2010
.Dt MAKE 1
.Os
.Sh NAME
@@ -536,11 +536,48 @@
.Pq Ql \&$
the string is expanded again.
.Pp
-Variable substitution occurs at two distinct times, depending on where
+Variable substitution occurs at three distinct times, depending on where
the variable is being used.
+.Bl -enum
+.It
Variables in dependency lines are expanded as the line is read.
+.It
Variables in shell commands are expanded when the shell command is
executed.
+.It
+.Dq .for
+loop index variables are expanded on each loop iteration.
+Note that other variables are not expanded inside loops so
+the following example code:
+.Bd -literal -offset indent
+
+.Dv .for i in 1 2 3
+a+= ${i}
+j= ${i}
+b+= ${j}
+.Dv .endfor
+
+all:
+ @echo ${a}
+ @echo ${b}
+
+.Ed
+will print:
+.Bd -literal -offset indent
+1 2 3
+3 3 3
+
+.Ed
+Because while ${a} contains
+.Dq 1 2 3
+after the loop is executed, ${b}
+contains
+.Dq ${j} ${j} ${j}
+which expands to
+.Dq 3 3 3
+since after the loop completes ${j} contains
+.Dq 3 .
+.El
.Ss Variable classes
The four different classes of variables (in order of increasing precedence)
are:
