Help scrolling and number of lines in a shell

Question

I'm programming in C and I need to know the number of lines of stdin. After a certain number of lines, I also need to scroll up one line...I used an ANSI escape code (033[1S), but I lose the content of the line scrolled and I don't wanna this.

EDIT: Simple code to explain the 2nd point

#include <stdio.h>

int main(void) { 
    printf("one\ntwo\nthree\n"); 
    fputs("\033[1S", stdout);
return 0; 
}

Answer 1

this is a good reference for the ansi escape codes scroll down the page to the table of codes.

I believe you may need \033[1E in addition to "1S" to move down onto the new line. play around with the codes.

also I think you can get the lines/cols from the environment.

below code thanks to "Hko" from http://www.linuxquestions.org/questions/programming-9/linux-c-syscall-to-get-number-of-columns-of-current-terminal-250252/

#include <sys/types.h>
#include <sys/ioctl.h>
#include <stdio.h>

int main()
{
    struct winsize ws; 

    ioctl(1, TIOCGWINSZ, &ws);
    printf("Columns: %d\tRows: %d\n", ws.ws_col, ws.ws_row);
    return 0;
}

Answer 2

it looks like you're mistaken about what stdin is.

in your example int the comments:

#include <stdio.h> 
int main(void) { 
  int c; int i = 1; 
  printf("one\ntwo\nthree\n"); 
  //while((c=fgetc(stdin)) != NULL) { 
  // comparing it with null is not correct here
  // fgetc returns EOF when it encounters the end of the stream/file
  // which is why an int is returned instead of a char
  while((c=fgetc(stdin)) != EOF) { 
    if (c=='\n') { 
      printf("%d\n", i); i++; 
    } 
  } 
  return 0; 
}

calling the program from the command line should output this

$ prog
one
two
three

you must send it a stream or a pipe to give it information through stdin

$ cat myfile | prog
one
two
three
4 # or however many lines are in myfile

stdin is blank by default. if you type into it, nothing is sent until you hi enter

this is what I see from compiling hte above code:

1 ./eof_testing
one
two
three
jfklksdf #my typing here
1
fjklsdflksjdf #mytyping here
2
fjklsdflksdfjf # my typing here
3

----- adding example of stty system call ----

#define STDIN_FD 0
#define STDOUT_FD 1 
#define CHUNK_SIZE 8

#define QUIT_CHAR (char)4 /* C-D */
int main(){
  write(STDOUT_FD,"hi\n",3);
  char buff[CHUNK_SIZE];
  int r, i;
  system("stty -echo raw");
  while(r = read(STDIN_FD, &buff, CHUNK_SIZE)){
    for(i = 0; i < r; i++){
      if(buff[i] == QUIT_CHAR)
        goto exit;
    }
    write(STDOUT_FD, &buff, r);
  }
  exit:
    system("stty echo cooked");
    return 0;
}

now, however there is a whole new set of challenges to tackle, such as the key sends the '\r' character so instead of a newline it just returns to the start of the line. this is because now that the characters go directly to the program, lines are not terminated with the '\n' character which was happening in 'cooked' mode by the terminal.

http://starboard.firecrow.com/interface_dev/mle.git/editor/editor.c