How do I unset (undo) unix set -C in zsh?
This works as expected
$ echo "foo" > foo
$ cat foo # foo
$ echo "updated" > foo
$ cat foo # updated
From man set
-C If set, bash does not overwrite an existing file with the
>, >&, and <> redirection operators. This may be overridden
when creating output files by using the redirection operator
>| instead of >.
Ok, so let's set -C
$ set -C
$ echo "bar" > bar
$ cat bar # bar
$ echo "updated" > bar
file exists: bar
This is all well and good, but now it's time to turn off set -C.
How do i disable set -C after it's been turned on?
I've tried:
$ unset -C
zsh: bad option: -C
Solution 1:
Blah. It's as simple as
$ set +C
Of course I find the answer immediately after posting the question.
The man pages don't really mention the difference between + and -.
Solution 2:
It seems you are using the Z shell, but quote the bash man page.
Just to clarify, the set -C and set +C commands work also in zsh, but more easily to memorize are IMHO shell options:
setopt no_clobber
This is equivalent to set -C. And, to disable this option, there is indeed a unsetopt builtin:
unsetopt no_clobber
All options are listed with man zshoptions. Options are kind of symmetric, so setopt no_clobber is equivalent to unsetopt clobber. That's why, in the man page the CLOBBER option is explained:
CLOBBER (+C, ksh: +C)
Allows
>redirection to truncate existing files, and>>to create files. Otherwise>!or>|must be used to truncate a file, and>>!or>>|to create a file.
A related option (IMHO very handy) is
HIST_ALLOW_CLOBBER
Add
|to output redirections in the history. This allows history references to clobber files even when CLOBBER is unset.
Demo:
zsh$ setopt no_clobber hist_allowclobber zsh$ echo foo > baz zsh$ echo bar > baz zsh: file exists: baz zsh$ [Arrow UP] zsh$ echo bar >| baz zsh$
And as a last remark, options are case-insensitive and underscores are ignored, hence NOCLOBBER, NO_clobber, noclobber are treated the same way.