* [PATCH 1/2] FAQ: Add "Why does my bash script report an error when I run it under zsh?".
@ 2020-05-28 20:30 Daniel Shahaf
2020-05-28 20:30 ` [PATCH 2/2] FAQ (3.1): Update ksh compatibility answer for reserved word typeset Daniel Shahaf
0 siblings, 1 reply; 2+ messages in thread
From: Daniel Shahaf @ 2020-05-28 20:30 UTC (permalink / raw)
To: zsh-workers
---
Uses emdash() from 45791.
Etc/FAQ.yo | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 54 insertions(+), 3 deletions(-)
diff --git a/Etc/FAQ.yo b/Etc/FAQ.yo
index d1f8b7d83..9b5e2206a 100644
--- a/Etc/FAQ.yo
+++ b/Etc/FAQ.yo
@@ -129,6 +129,7 @@ Chapter 3: How to get various things to work
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?
+3.31. Why does my bash script report an error when I run it under zsh?
Chapter 4: The mysteries of completion
4.1. What is completion?
@@ -857,6 +858,7 @@ mytt(compctl)
sect(Similarities with bash)
+label(25)
The Bourne-Again Shell, bash, is another enhanced Bourne-like shell;
the most obvious difference from zsh is that it does not attempt to
@@ -959,9 +961,9 @@ label(31)
Unless you need strict sh/ksh compatibility, you should ask yourself
whether you really want this behaviour, as it can produce unexpected
effects for variables with entirely innocuous embedded spaces. This
- can cause horrendous quoting problems when invoking scripts from
- other shells. The natural way to produce word-splitting behaviour
- in zsh is via arrays. For example,
+ can cause horrendous quoting problems when invoking scripts written
+ for other shells (see link(3.31)(331)). The natural way to produce
+ word-splitting behaviour in zsh is via arrays. For example,
verb(
set -A array one two three twenty
)
@@ -2034,6 +2036,55 @@ sect(Why doesn't the expansion mytt(*.{tex,aux,pdf}) do what I expect?)
parse!
+sect(Why does my bash script report an error when I run it under zsh?)
+label(331)
+
+ bash and zsh are different programming languages. They are not
+ interchangeable; programs written for either of these languages will,
+ in general, not run under the other. (The situation is similar with
+ many other pairs of closely-related languages, such as Python 2 and
+ Python 3; C and C++; and even C89 and C11.)
+
+ So, don't run bash scripts under zsh. If the scripts were written for
+ bash, run them in bash. There's absolutely no problem with having
+ mytt(#!/usr/bin/env bash) scripts even if mytt(zsh) is your shell for
+ interactive sessions.
+
+ In fact, if you've recently changed to zsh, we myem(recommend) that
+ you keep your scripts as mytt(#!/usr/bin/env bash), at least for
+ a while: this would make the change more gradual and flatten your
+ learning curve. Once you're used to zsh, you can decide for each
+ script whether to port it to zsh or keep it as-is.
+
+ That's the answer for myem(scripts), i.e., for external commands that
+ are located in tt($PATH), or located elsewhere and are executed by
+ giving their path explicitly (as in mytt(ls), mytt(/etc/rc.d/sshd),
+ and mytt(./configure)). For myem(plugins) emdash() code that is
+ executed within the shell itself, that's loaded via the mytt(.),
+ mytt(source), or mytt(autoload) builtins, added to mytt(.zshrc), or
+ pasted interactively at the shell prompt emdash() the answer is
+ different.
+
+ Since the bash and zsh languages do have a common subset, it is
+ feasible to write non-trivial plugins that would run under either of
+ them, if one is sufficiently familiar with both of them. However,
+ a difference between bash's behaviour and zsh's does not imply that
+ zsh has a bug. It myem(might) be a bug in zsh, but it might also be
+ a bug in bash, or simply a difference that isn't a bug in either shell
+ (see link(3.1)(31) for an example).
+
+ When bash and zsh behave differently on the same input, whether zsh's
+ behaviour is a bug does not depend on what bash does on the same
+ input; rather, it depends on what zsh's user manual specifies.
+ (By way of comparison, it's not a bug in Emacs that mytt(:q!) doesn't
+ cause it to exit.)
+
+ If you'd like to run a bash script under zsh, you must port the script
+ properly, reviewing it line by line for differences between the two
+ languages and adjusting the script accordingly, just like you would
+ when translating a book from American English to British English.
+
+
chapter(The mysteries of completion)
^ permalink raw reply [flat|nested] 2+ messages in thread
* [PATCH 2/2] FAQ (3.1): Update ksh compatibility answer for reserved word typeset.
2020-05-28 20:30 [PATCH 1/2] FAQ: Add "Why does my bash script report an error when I run it under zsh?" Daniel Shahaf
@ 2020-05-28 20:30 ` Daniel Shahaf
0 siblings, 0 replies; 2+ messages in thread
From: Daniel Shahaf @ 2020-05-28 20:30 UTC (permalink / raw)
To: zsh-workers
---
Reported in 45922. I dropped the sentence about bash because I couldn't
figure out what it was referring to with the term "this behaviour".
bash on my system does word-split arguments that look like assignments
with backticks on the RHS for commands other than «typeset».
Etc/FAQ.yo | 28 +++++++++++++++++++---------
1 file changed, 19 insertions(+), 9 deletions(-)
diff --git a/Etc/FAQ.yo b/Etc/FAQ.yo
index 9b5e2206a..a327eb514 100644
--- a/Etc/FAQ.yo
+++ b/Etc/FAQ.yo
@@ -981,7 +981,7 @@ label(31)
been automatic word splitting in scalars, which is a sort of
uncontrollable poor man's array.
- Note that this happens regardless of the value of the internal field
+ Note that word splitting happens regardless of the value of the internal field
separator, tt($IFS); in other words, with mytt(IFS=:; foo=a:b; args $foo)
you get the answer 1.
@@ -1013,22 +1013,32 @@ label(31)
or (entirely equivalent) when mytt(emulate ksh) or mytt(emulate sh) is in
effect.
- There is one other effect of word splitting which differs between ksh
+ There used to be another effect of word splitting which differed between ksh
and zsh. In ksh, the builtin commands that declare parameters such
as tt(typeset) and tt(export) force word-splitting not to take place
after on an assignment argument:
verb(
typeset param=`echo foo bar`
)
- in ksh will create a parameter with value mytt(foo bar), but in zsh will
+ in ksh will create a parameter with value mytt(foo bar).
+
+ zsh used to
create a parameter tt(param) with value tt(foo) and a parameter tt(bar)
- whose value is empty. Contrast this with a normal assignment (no
+ whose value was empty. Contrast this with a normal assignment (no
tt(typeset) or other command in front), which never causes a word split
- unless you have tt(GLOB_ASSIGN) set. From zsh version 4.0.2 the option
- tt(KSH_TYPESET), set automatically in compatibility mode, fixes this
- problem. Note that in bash this behaviour occurs with all arguments that
- look like assignments, whatever the command name; to get this behaviour
- in zsh you have to set the option tt(MAGIC_EQUAL_SUBST).
+ unless you have tt(GLOB_ASSIGN) set.
+
+ zsh version 4.0.2 and newer creates a single parameter with value
+ mytt(foo bar), like ksh does, when the option tt(KSH_TYPESET) is set.
+ This option gets set automatically when in ksh compatibility mode.
+
+ zsh 5.1 and newer create a single parameter with value mytt(foo bar) by
+ default, in both compatibility and native modes. The older behaviour
+ can be obtained with mytt(disable -r typeset).
+
+ If the options mytt(MAGIC_EQUAL_SUBST) and mytt(KSH_TYPESET) are both
+ set, arguments that look like assignments will not undergo word
+ splitting, whatever the command name.
sect(In which startup file do I put...?)
^ permalink raw reply [flat|nested] 2+ messages in thread
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2020-05-28 20:30 [PATCH 1/2] FAQ: Add "Why does my bash script report an error when I run it under zsh?" Daniel Shahaf
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