bash - 为什么 ZSH 卡在空重定向上？

Question

要在 unixy 环境中截断文件，您通常会使用:

$ > file

在 bash(也是破折号)中，文件被截断(如果不存在则创建)，然后提示符返回。在 zsh 中，文件被截断/创建，但挂起。您必须 Ctrl-C 才能再次使用提示。

重定向非空输出没有问题:

zsh$ cat nonempty.file > file
zsh$

问题是:

这种行为是否符合预期？ zsh 错误吗？

Answer 1

我不是真正的 zsh 用户，但看起来 zsh 中的 > file 与 bash 中的 cat > file 相同。要在 zsh 中创建新文件或截断它，请使用 : > file。这也适用于 bash。

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更新:

在 zsh 手册中找到:

• REDIRECTIONS WITH NO COMMAND:

  When a simple command consists of one or more redirection operators and zero or more parameter assignments, but no command name, zsh can behave in several ways.

  If the parameter NULLCMD is not set or the option CSH_NULLCMD is set, an error is caused. This is the csh behaviorand CSH_NULLCMD is set by default when emulating csh.

  If the option SH_NULLCMD is set, the builtin : is inserted as a command with the given redirections. This is thedefault when emulating sh or ksh.

  Otherwise, if the parameter NULLCMD is set, its value will be used as a command with the given redirections. If bothNULLCMD and READNULLCMD are set, then the value of the latter will be used instead of that of the former when theredirection is an input. The default for NULLCMD is cat and for READNULLCMD is more.

在我的系统上，默认是:

$ echo $ZSH_VERSION
4.3.10
$ echo $NULLCMD
cat
$ echo $READNULLCMD
/usr/bin/pager
$