child process infinite loop with execve

Question

Here is my pipe to pipe function:

• int *pip is the pipe that I want to read from
• char **cmd is the command that I want to execute
• char **envp points to the environment variables

I want to take the pipe (pip) as STDIN with dup2 and take the new pipe (fd) as STDOUT also with dup2

The problem is that when it comes to execve the command is executed but the program is stuck in an infinite loop

int *pipe_to_pipe(int *pip, char **cmd, char **envp) {

    int     *fd;
    int     pid;

    fd = (int *)malloc(sizeof(int) * 2);
    if (!fd || pipe(fd) == -1)
            error(1);
    pid = fork();
    if (pid == -1)
            error(1);
    if (pid == 0)
    {
            dup2(pip[0], STDIN_FILENO);
            dup2(fd[1], STDOUT_FILENO);
            close(fd[0]);
            close(pip[1]);
            execve((command_path), cmd, envp);
            exit(0);
    }
    wait(NULL);
    free(pip);
    return (fd);
}

As an example, if I have "hello world" in my int *pip as a char **cmd I have cmd[0] = "cat", cmd[1] = "-e". When I make execve(path, cmd, envp); the program cat "hello world" and infinite loop here.

How can I fix this?

Answer 1

The problem comes from the fact that I didn't close the pipe "pip" in the parent process adding those lines that would be executed by the parent process fix everything

if (pid != 0){
close(pip[0]);
close(pip[1]);
wait(NULL);
}

Otherwise it fixes my problem I don't understand why if someone can explain to me I will be gratefull Thanks to everyone that answered me <3