在 perl 中使用 -e 和 -s 开关 [英] Using -e and -s switch in perl

问题描述

我开始学习 Perl.我试过了

I am starting to lern Perl. I tried

perl -e 'print "The value of \$x=$x\n";'

给出:

The value of $x=

鉴于:

perl -s -x=10 -e 'print "The value of \$x=$x\n";'

给予

No Perl script found in input

我想将 -s 开关与 -e 开关一起使用.. 为什么它不起作用?

I would like to use the -s switch together with -e switch.. Why is it not working?

推荐答案

脚本本身的参数应该在之后出现，无论它是单行还是文件.虽然并非总是必要的，但您可以使用 -- 将 perl 的参数与脚本的参数分开:

Arguments to the script itself should come after the script, regardless of whether it's a one-liner or a file. While not always necessary, you can separate the arguments for perl from the arguments to your script with a --:

$ perl -s -E'say "\$x=$x"' -- -x=42
x=42

用 -- 结束 perl 的参数是必要的，因为 -x 是 perl 本身理解的标志，所以你的脚本永远不会看到它.来自 perldoc perlrun:

Ending the arguments to perl with -- is necessary because -x is a flag understood by perl itself, so your script would never see it. From perldoc perlrun:

告诉 Perl 该程序嵌入在一大块不相关的文本中，例如邮件消息中.前导垃圾将被丢弃，直到第一行以#!"开头；并包含字符串perl".将应用该行上任何有意义的开关.

-x

-xdirectory

tells Perl that the program is embedded in a larger chunk of unrelated text, such as in a mail message. Leading garbage will be discarded until the first line that starts with "#!" and contains the string "perl". Any meaningful switches on that line will be applied.

[…]

如果指定了目录名，Perl 将在运行程序之前切换到该目录.-x 开关仅控制主要垃圾的处理.程序必须以END"结束.如果有尾随垃圾要忽略；程序可以通过DATA"处理任何或所有尾随垃圾.如果需要，可以使用文件句柄.

If a directory name is specified, Perl will switch to that directory before running the program. The -x switch controls only the disposal of leading garbage. The program must be terminated with "END" if there is trailing garbage to be ignored; the program can process any or all of the trailing garbage via the "DATA" filehandle if desired.

目录(如果指定)必须紧跟在 -x 之后且中间没有空格.

The directory, if specified, must appear immediately following the -x with no intervening whitespace.

作为指定的输入 print "The value of \$x=$x\n"; 不包含shebang，未找到实际脚本，因此您遇到的错误是发出.

As the specified input print "The value of \$x=$x\n"; does not contain a shebang, the actual script wasn't found and thus the error you encountered was emitted.

不要使用 -s 开关解析，除了最​​简单的单行代码.改用 Getopt::Long.

Do not use -s switch parsing for any but the most simple one-liners. Use Getopt::Long instead.

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