From 61a697f977cd5152c15d9fd3a3628826d2b5fc52 Mon Sep 17 00:00:00 2001
From: Peter Stephenson
Date: Mon, 8 Jul 2019 14:27:08 +0100
Subject: users/24030 (minor tweak): note on *.{bla,hbl,ahb}.
This is an expansion, not a form of pattern match. Describe
the problem and what to do instead.
---
ChangeLog | 5 +++++
Etc/FAQ.yo | 39 +++++++++++++++++++++++++++++++++++++++
2 files changed, 44 insertions(+)
diff --git a/ChangeLog b/ChangeLog
index a73915f3e..78efc455c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2019-07-08 Peter Stephenson
+
+ * users/24030: Etc/FAQ.yo: Note that *.{bla,hbl,ahb} is an
+ expansion, not a pattern match, and what to do instead.
+
2019-07-02 Peter Stephenson
* 44480: Doc/Zsh/mod_socket.yo, Doc/Zsh/mod_system.yo,
diff --git a/Etc/FAQ.yo b/Etc/FAQ.yo
index c4f65e97a..be4e1f8a8 100644
--- a/Etc/FAQ.yo
+++ b/Etc/FAQ.yo
@@ -128,6 +128,7 @@ Chapter 3: How to get various things to work
3.27. What are these `^' and `~' pattern characters, anyway?
3.28. How do I edit the input buffer in $EDITOR?
3.29. Why does `which' output for missing commands go to stdout?
+3.30. Why doesn't the expansion mytt(*.{tex,aux,pdf}) do what I expect?
Chapter 4: The mysteries of completion
4.1. What is completion?
@@ -1995,6 +1996,44 @@ sect(Why does `which' output for missing commands go to stdout?)
the exit status does reflect the fact the command can't be found.
+sect(Why doesn't the expansion mytt(*.{tex,aux,pdf}) do what I expect?)
+
+ Based on the behaviour of some other shells, you might guess that the
+ following expression:
+ verb(
+ echo *.{tex,aux,pdf}
+ )
+ would be the way to echo any files ending in mytt(.tex), mytt(.aux) or
+ mytt(.pdf) in the current directory. Depending on your settings for
+ matching (see link(2.1)(21), in particular tt(NO_NOMATCH)), you may
+ see something else, in particular an error about (say) mytt(*.aux) if
+ there were no files ending mytt(.aux).
+
+ The reason for this is that the brace expansion isn't actually
+ a form of pattern matching. Instead, the line above is equivalent to
+ verb(
+ echo *.tex *.aux *.pdf
+ )
+ giving you three separate patterns. With the default mytt(NOMATCH)
+ behaviour in effect, any pattern that fails to match is an error.
+
+ However, there em(is) a way of doing exactly what you want, using
+ parentheses instead of braces:
+ verb(
+ echo *.(tex|aux|pdf)
+ )
+ This is now a pattern matching expression, so is considered as a
+ single pattern. Now any file that exists will supress the
+ mytt(NOMATCH) behaviour, but you'll still get all the files that do
+ match.
+
+ This use of parentheses is special to zsh. Modern Bourne-like shells
+ have a syntax like this, too, but with an mytt(@) in front of the
+ parentheses: again, see link(2.1)(21), and search for mytt(@+LPAR()).
+ This is harder for the user to remember but easier for the shell to
+ parse!
+
+
chapter(The mysteries of completion)
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