Programming

i made a function similar to peopen, how can i test if it works?

Code:

    FILE *file_pointer; char output[512];
    file_pointer = popen_new(COMMAND, "r");
    size_t bytes = read(fileno(file_pointer), output, 512); 
    printf(output);
    pclose_new(file_pointer);

this gave me the expected output

Code:

    file_pointer = popen_new(TEST_COMMAND, "w");
    write(fileno(file_pointer), output, bytes); 
    pclose_new(file_pointer);

this one i also get expected results, but i am still not sure if its right, the output was the result of the COMMAND string, but what can i do after writing to see if it worked, i cant read it since its in write mode...

Redirect its output into a file?

Or just leave its stdout unredirected, to write to console?

the output is coming to stdout and i can see it, does this mean it works exactly like what popen does with a "w" argument?, i get no warnings or errors, and the code is pretty much what you saw before. except i changed it from structures to
arrays, because i know i will at most have 20 streams

so i have a int array, a int variable, and a file pointer array

int count = 0;
FILE *fp_array[25];
pid_t pid_array[25];

these are global

fp_array[count] = open_file;
pid_array[count++] = pid;

this happens when i use popen_new

and then when i pclose_new
i loop theough fp_array and see if the value matched the given fp, and if so i have access to its pid, so i can wait for the process to finish using a while loop and waitpid, also close it, and then return the status variable since thats what i code i posted up before did.

this is my pclose_new
also when getting the exit code using pclose_new for the popen_new using "r" i get the return to be 141 but when used by "w" i get 0.....
why am i getting 141


also can a pointer to a file ever be the value 0 and can a pid value ever be 0?

Huh. Actually, you can count on a global variable being NULL or zero when the program starts.

You should probably use WEXITSTATUS(status).

I think it works like it does with popen. You might want to actually try popen to be sure.

what about

also when getting the exit code using pclose_new for the popen_new using "r" i get the return to be 141 but when used by "w" i get 0.....
why am i getting 141


also can a pointer to a file ever be the value 0 and can a pid value ever be 0?

I can't tell from here. Please post your current code and exactly what you did with it. No. Then you wouldn't be able to tell it apart from NULL. No.

so if i set an element of a file_pointer array to 0, and then i compare NULL to that value 0, will it crash or just result to false, cause i set the file pointer array and pid array to 0, after closing its respective file pointer. this is like removing the struct from the chain of structs, but using an array method.

also
for the popen_new function
the instruction given was ls; ls