为什么要执行“sh -c a.out"?而不是 a.out 本身? [英] Why should one exec "sh -c a.out" instead of a.out itself?

问题描述

我正在 https://opensource.apple.com/source/Libc/Libc-167/gen.subproj/popen.c.auto.html 并注意到他们做 execl(_PATH_BSHELL, "sh", "-c", command, NULL) 而不是 execl(_PATH_BSHELL, command, NULL).

I'm studying Apple's implementation of popen() at https://opensource.apple.com/source/Libc/Libc-167/gen.subproj/popen.c.auto.html and noticed that they do execl(_PATH_BSHELL, "sh", "-c", command, NULL) instead of execl(_PATH_BSHELL, command, NULL).

你为什么要(或应该)执行一个可执行文件，例如a.out 通过 sh -c 而不是可执行文件本身?

Why would you want to (or should you) exec an executable, e.g. a.out via sh -c instead of just the executable itself?

如果你 exec sh -c a.out 而不是 a.out 本身，实际的 a.out 过程是否会结束成为孙子"进程而不是子进程?

If you exec sh -c a.out instead of just a.out itself, does the actual a.out process end up being a "grandchild" process and not a child process?

推荐答案

你为什么要(或应该)执行一个可执行文件，例如a.out 通过 sh -c 而不是可执行文件本身?

Why would you want to (or should you) exec an executable, e.g. a.out via sh -c instead of just the executable itself?

popen() 旨在运行包含 shell 语法的 shell 命令，例如 > 重定向、| 管道和 && 命令链.它需要通过 sh -c 传递字符串以支持这些结构.如果没有，这些语法特征将作为参数逐字传递给相关程序.

popen() is designed to run shell commands that include shell syntax like > redirection, | pipes, and && command chaining. It needs to pass the string through sh -c in order to support those constructs. If it didn't those syntactical features would be passed verbatim to the program in question as arguments.

例如，popen("make clean && make") 应该触发两个 make 调用.如果没有 sh -c，它会用三个参数调用 make 一次，就好像已经输入了

For example, popen("make clean && make") should trigger two make invocations. Without sh -c it would call make once with three arguments, as if one had typed

$ make clean '&&' make

在终端.

如果你 exec sh -c a.out 而不是 a.out 本身，实际的 a.out 过程是否会结束成为孙子"进程而不是子进程?

If you exec sh -c a.out instead of just a.out itself, does the actual a.out process end up being a "grandchild" process and not a child process?

是的，没错.当前进程和a.out之间会有一个sh进程.

Yes, that is correct. There will be a sh process in between the current process and a.out.

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