Thread: Input and output redirection together !!

Hi,

I am trying to implement redirections. I am able to get the result for input and output redirection, individually. However, when I do both together I see not o/p.


file_input - Input file
file_output - output file
cmd - the command that will get exected
argv - arguments
symbol - tell which is the redirection

Code:

//Function that exectues commands involving redirection
int execute_redirect_command(char file_input[], char file_output[], char cmd[], char **argv, char symbol[])
{
    FILE *input_ptr, *output_ptr;
    int fd;
    if(fork() == 0)
    {
        if(file_input != NULL)
        {
            input_ptr = fopen(file_input,"r");
            fd = fileno(input_ptr);
            dup2(fd,0);
            close(fd);
        }
        if(file_output != NULL)
        {
            if(strcmp(symbol,">>") == 0)
            {
                output_ptr = fopen(file_output,"a");
            }
            else
            {
                output_ptr = fopen(file_output,"w");
            }
            fd = fileno(output_ptr);
            dup2(fd,1);
            close(fd);
        }
        execvp(cmd, argv);
    }
    else
    {
        wait(NULL);
    }
}

Above is my code. Also would like to know how to do error handling here.

Thanks in advance.

You need to post a complete (non-)working program.

The only error I see in your code is that you ignore the function error returns.

Examples:

Code:

pid = fork();
if (pid == 0)
else if (pid == -1)
    perror("fork");
else
    wait(NULL);


if (input_ptr == NULL) perror("fopen input");

if (dup2(fd,0) == -1) perror("dup2 0");

if (execvp(cmd, argv) == -1) perror("execvp");