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authorPeter Stephenson <pws@users.sourceforge.net>2005-09-23 17:03:16 +0000
committerPeter Stephenson <pws@users.sourceforge.net>2005-09-23 17:03:16 +0000
commitad2bd42c858aa7236e7b7404806d16b5b0efb6ac (patch)
tree3c7fd50ab1014769c6d59d15145aefca37ed02be /Doc/Zsh/expn.yo
parentced5aab522df2754c2fa4581c3538c2cb6d4c1e1 (diff)
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21758: optimise =(<<<...) to run within the shell.
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@@ -340,6 +340,15 @@ process.  This may be used instead of the tt(<)
 form for a program that expects to lseek (see manref(lseek)(2))
 on the input file.
 
+There is an optimisation for substitutions of the form
+tt(=LPAR()<<<)var(arg)tt(RPAR()), where var(arg) is a single-word argument
+to the here-string redirection tt(<<<).  This form produces a file name
+containing the value of var(arg) after any substitutions have been
+performed.  This is handled entirely within the current shell.  This is
+effectively the reverse of the special form tt($LPAR()<)var(arg)tt(RPAR())
+which treats var(arg) as a file name and replaces it with the file's
+contents.
+
 The tt(=) form is useful as both the tt(/dev/fd) and the named pipe
 implementation of tt(<LPAR())var(...)tt(RPAR()) have drawbacks.  In 
 the former case, some programmes may automatically close the file