c -/vs.\in CMD 和 C 系统函数中可执行文件的相对路径

Question

考虑以下 Windows 10 上的 CMD session ，以 # 开头的行是注释:

# We have this simple program
D:\testdir>type prg.c
#include <stdio.h>

int main() {
  printf("Hello prg");
  return 0;
}
# This is "realgcc.exe (Rev2, Built by MSYS2 project) 6.2.0"
D:\testdir>gcc prg.c -o prg
D:\testdir>prg.exe
Hello prg
D:\testdir>md dir
D:\testdir>cd dir
D:\testdir\dir>..\prg.exe
Hello prg
# This does not work however
D:\testdir\dir>../prg.exe
'..' is not recognized as an internal or external command,
operable program or batch file.
# But this does
D:\testdir\dir>"../prg.exe"
Hello prg
# Now we want to call the same program, from the same directory,
# but from C instead, so we create this file
D:\testdir\dir>type call.c
#include <stdlib.h>

int main() {
  system("..\\prg.exe");
  return 0;
}
D:\testdir\dir>gcc call.c -o call
D:\testdir\dir>call.exe
Hello prg
# Now to the question: If we modify the system function call
# to the following -- why doesn't it work?
D:\testdir\dir>type call.c
#include <stdlib.h>

int main() {
  system("\"../prg.exe\"");
  return 0;
}
D:\testdir\dir>gcc call.c -o call
D:\testdir\dir>call.exe
'..' is not recognized as an internal or external command,
operable program or batch file.

显然调用 system 与在 CMD session 中交互式运行命令不同？引号是否出于某种原因被删除？是否有另一种语法可用于使用包含 / 而不是 \ 作为分隔符的相对路径来调用其他目录中的可执行文件？

(我在尝试让 Cygwin 程序和普通的 Windows 程序相互对话时注意到这一点。)

编辑:显然，这行得通:

#include <stdlib.h>

int main() {
  system("\"\"../prg.exe\"\"");
  return 0;
}

可能相关，在CMD中，

cmd /c ""../prg.exe""

有效，而这个无效

cmd /c "../prg.exe"

所以似乎在 system 调用中出于某种原因需要一些额外的引号？

Answer 1

感谢您提供所有有用的评论，我现在明白发生了什么。在问这个问题时，我没有考虑命令(即 system 的参数)实际上是如何传递给“命令解释器”的，这是理解为什么外部引号消失的关键.

在 Windows 上，调用 system("command") 本质上与使用参数 /c< 生成一个新的 cmd.exe 进程是一样的 和 命令。 (在 Linux and similar OSes 上，我们将与 sh -c command 等价。)

然而，这里的问题是，在大多数情况下，当通过 /c 标志传递命令时，Windows 的 CMD 将去除第一个和最后一个引号字符。这在 cmd/? 给出的文档中有说明:

[...]

If /C or /K is specified, then the remainder of the command line after
the switch is processed as a command line, where the following logic is
used to process quote (") characters:

1.  If all of the following conditions are met, then quote characters
    on the command line are preserved:

    - no /S switch
    - exactly two quote characters
    - no special characters between the two quote characters,
      where special is one of: &<>()@^|
    - there are one or more whitespace characters between the
      two quote characters
    - the string between the two quote characters is the name
      of an executable file.

2.  Otherwise, old behavior is to see if the first character is
    a quote character and if so, strip the leading character and
    remove the last quote character on the command line, preserving
    any text after the last quote character.

[...]