c - bash : ./comp.out:权限被拒绝

Question

我正在尝试编写一个程序来比较 2 个文件并返回它们是否相等。

我只能使用函数:fork、dup、dup2、open、write 、exec 和 read。

当我在 linux gcc 上编译程序时，它返回:

bash: ./comp.out: Permission denied

代码:

#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

int CheckSimilar(char *path1, char *path2);

int main(int argc, char **argv) {

    int returnValue = CheckSimilar(argv[1], argv[2]);

    switch (returnValue){

        case 1:
            write(1, "1\n", 3);
            break;
        case 2:
            write(1, "2\n", 3);
            break;
        case 3:
            write(1, "3\n", 3);
            break;
        default:
            break;
    }

    return 0;
}

/*
* This function checks if the files are similar or similar by case     sensitive
* it gets 2 files, and returns: 3 if identical, 2 if identical but only if not
* case sensitive or 1 else.
*/

如何更改权限？

shay@shay-Latitude-E6410 ~/workspace/targ1OS $ gcc -c ec11.c -o      comp.out
shay@shay-Latitude-E6410 ~/workspace/targ1OS $ ls
comp.out  Debug  ec11.c
shay@shay-Latitude-E6410 ~/workspace/targ1OS $ ./comp.out       /home/shay/Downloads/input.txt /home/shay/Downloads/input.txt
bash: ./comp.out: Permission denied
shay@shay-Latitude-E6410 ~/workspace/targ1OS $ comp.out /home/shay/Downloads/input.txt /home/shay/Downloads/input.txt
comp.out: command not found
shay@shay-Latitude-E6410 ~/workspace/targ1OS $ ./comp.out /home/shay/Downloads/input.txt /home/shay/Downloads/input.txt
bash: ./comp.out: Permission denied
shay@shay-Latitude-E6410 ~/workspace/targ1OS $ ^C
shay@shay-Latitude-E6410 ~/workspace/targ1OS $ ls -al ./comp.out
-rw-r--r-- 1 shay shay 2640 Mar 30 10:05 ./comp.out
shay@shay-Latitude-E6410 ~/workspace/targ1OS $ chmod ogu+x ./comp.out
shay@shay-Latitude-E6410 ~/workspace/targ1OS $ ./comp.out /home/shay/Downloads/input.txt /home/shay/Downloads/input.txt
bash: ./comp.out: cannot execute binary file: Exec format error
shay@shay-Latitude-E6410 ~/workspace/targ1OS $ gcc -c ec11.c -o comp.out
shay@shay-Latitude-E6410 ~/workspace/targ1OS $ ./comp.out /home/shay/Downloads/input.txt /home/shay/Downloads/input.txt
bash: ./comp.out: Permission denied
shay@shay-Latitude-E6410 ~/workspace/targ1OS $ chmod ogu+x ./comp.out
shay@shay-Latitude-E6410 ~/workspace/targ1OS $ ./comp.out /home/shay/Downloads/input.txt /home/shay/Downloads/input.txt
bash: ./comp.out: cannot execute binary file: Exec format error
shay@shay-Latitude-E6410 ~/workspace/targ1OS $ comp.out /home/shay/Downloads/input.txt /home/shay/Downloads/input.txt
comp.out: command not found

Answer 1

命令

gcc -c ec11.c -o      comp.out

创建一个目标文件，而不是一个可执行程序文件。目标文件是编译的 translation units (包含所有头文件的大致源文件)仅此而已。 -c 标志告诉编译器 fronteng 程序 gcc 创建目标文件，因此要么删除 -c 标志，要么显式链接.

所以要么

$ gcc ec11.c -o comp.out

或者

$ gcc -c ec11.c
$ gcc ec11.o -o comp.out

---

另外，我建议您在编译时添加警告标志，这样编译器会针对可能在运行时引起问题的事情(例如未定义的行为或逻辑/语义问题)向您发出更多警告。我个人至少使用标志 -Wall -Wextra -pedantic。