find2perl perl shebang + eval的确切含义是什么? [英] What is the exact meaning of the find2perl perl shebang + eval?

问题描述

以下内容有什么作用?

#! /usr/bin/perl -w
    eval 'exec /usr/bin/perl -S $0 ${1+"$@"}'
        if 0; #$running_under_some_shell

• if 0永远不会为真，因此eval部分将永远不会执行，
• 并且评估也很奇怪-在这种情况下，$0的值是什么(在单引号内?)
• the if 0 is never true, so the eval part will never executed,
• and the eval is strange too - what is the value of $0 in this context (inside single quotes?)

Ps:取自find2perl命令的结果

Ps: taken from the result of the find2perl command

推荐答案

最佳猜测-如此注释#$running_under_some_shell所示，它用于检测脚本是否由除perl之外的其他shell运行，例如重击.

Best guess - as in this comment #$running_under_some_shell, it's to detect if the script is being run by some shell other than perl, e.g. bash.

如果0永远都不为真，那么评估部分将永远不会执行，

the if 0 is never true, so the eval part will never executed,

不是perl，不是.对于其他shell(例如bash)，它不会发现行继续，而只会执行eval语句.然后，这将在perl下重新运行该脚本. (奇怪的是，它的选项与hashbang行不同.)

Not by perl, no. By other shells such as bash it won't spot the line continuation and will just execute the eval statement. This then re-runs the script under perl. (Oddly with different options than the hashbang line.)

并且eval也很奇怪-在这种情况下，$ 0的值是多少(在单引号内?)

and the eval is strange too - what is the value of $0 in this context (inside single quotes?)

同样，它将通过bash而不是perl进行扩展:这意味着find2perl传递到perl解释器中的路径.

Again, this will be expanded by bash not perl: here it means the path to find2perl to pass into the perl interpreter.

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