c - execv 到 .c prog 使用相同的管道

Question

我必须编写一个运行 fork 的代码。子项目是另一个需要完成主要任务的项目。我运行 execv() 函数，但它找不到路径。子文件位于同一台计算机的其他项目中。

第二个问题:child 是我的程序。如何使其可执行？

int main(int argc, char **argv)
{
    int pipefd[2];
    pid_t cpid1; 
    char *checkRows[] = { "child", "-r", NULL };
    if (pipe(pipefd) == -1)
    {
        perror("pipe");
        exit(EXIT_FAILURE);
    }
    cpid1 = fork();
    if (cpid1 == 0)
    { // child 1
        printf("after fork %d", cpid1);
        dup2(pipefd[1], 1); // redirect stdout to pipe
        close(pipefd[0]);
        execv("child",checkRows);
        perror("execc rows failed");
    }
    else if (cpid1 == -1)
    { // fork failed
        printf("error!");
        exit(EXIT_FAILURE);
    }
    close(pipefd[1]);

    return EXIT_SUCCESS;
}

child

int main(int argc, char **argv)
{
    if (argc != 3){
        printf("there is no arguments pass");
        exit(EXIT_FAILURE);
    }
    printf("In child");
    return 0;
}

Answer 1

来自 execv(3):

 int
 execv(const char *path, char *const argv[]);

 The execv(), execvp(), and execvP() functions provide an array of point-
 ers to null-terminated strings that represent the argument list available
 to the new program.  The first argument, by convention, should point to
 the file name associated with the file being executed.  The array of
 pointers must be terminated by a NULL pointer.

来自 execvp(3) (实际上是相同的手册页):

 int
 execvp(const char *file, char *const argv[]);

 The functions execlp(), execvp(), and execvP() will duplicate the actions
 of the shell in searching for an executable file if the specified file
 name does not contain a slash ``/'' character.  For execlp() and
 execvp(), search path is the path specified in the environment by
 ``PATH'' variable.  If this variable isn't specified, the default path is
 set according to the _PATH_DEFPATH definition in <paths.h>, which is set
 to ``/usr/bin:/bin''.  For execvP(), the search path is specified as an
 argument to the function.  In addition, certain errors are treated spe-
 cially.

这意味着您可以使用

 execv("/absolute/patch/to/child",...)

作为替代解决方案，您可以使用

 execvp("child",...)

将“/absolute/patch/to”添加到路径中。

注意:这两个调用都是标准 C 库提供的库调用。 “exec 系列”的唯一系统调用是 execve()。