Question

Modify the mycat.c program to write to stderr the number of bytes that were read from stdin each time. You may use cLion inside VM, or any other text editor of your choice, such as vi or emacs. There is also a neat text editor named Kate available in Ubuntu (you can find it in the menu). In cLion you can open a single.cfile without having to create a whole new project and modify the single.c file. Find the mycat.c file and open it in the text editor tool you choose to use. In the command line terminal (shell), you can compile with "make all". This is going to create an executable file named "mycat". You can run it with "/mycat". A longer line to compile the mycat.c code on the command line terminal (shell) is with: gcc -ansi -1../include -DLINUX-D_GNU_SOURCE -Wall -o mycat mycat.c -.../lib-lapue This will produce the output file "mycat" and you can run it with "/mycat". Submit the mycat.c file (source code file) that you modified. This is the same program (mycat.c) as given in APUE. The program in Figure 3.5 copies a file, using only the read and write functions. #include "apue.h" #define BUFFSIZE 4096 int main(void) int n; char buf[BUFFSIZE]; while ((n = read (STDIN FILENO, buf, BUFFSIZE)) > 0) if (write(STDOUT_FILENO, buf, n) != n) err_sys("write error"); if (n < 0) err_sys("read error"); exit(0);

OPERATING SYSTEM... C , LINUX

Answer 1

I am getting error in err_sys function , so I just replaced that with perror and executed the program.. If your program compiles fine with err_sys then just use that along wth my modification to write to STDERR as below

#include<stdio.h>

#include<string.h>

#include<unistd.h>

#include<stdlib.h>

#define BUFFSIZE 4096

int main()

{

  int n;

  char buf[BUFFSIZE];

  while( (n = read(STDIN_FILENO, buf,BUFFSIZE))>0)

  {

    if(write(STDOUT_FILENO,buf,n)!=n)

      perror("Write error");

    //write to stderr

    sprintf(buf,"%d\n",n);

    write(STDERR_FILENO,buf,strlen(buf));

  }

  if( n < 0)

    perror("read error");

  exit(0);

}

====================================

//Output

 ./main
Hello World!
Hello World!
13
This is to test
This is to test
16

//screen shot

Repl.it - Online C Edi X C- Where is function x | +6 sprintf() in C - Geeks x 3 GDB online Debugge x + - X M Inbox (3,342) - bhag) C Computer Science q X € → C repl.it/languages/c Online C compiler, Online CIDE, and online C REPL. Code C, compile C, run C, and host your programs and apps online for free. save stop share + new repl 88 talk Sign up Files main.c main.c 3 saved 1 #include<stdio.h> 2 #include<string.h> #include<unistd.h> #include<stdlib.h> clang version 7.0.0-3-ubuntu0.18.04.1 (tags/RELEASE 700/final) 3 clang-7 -pthread-1m -o main main.c $ ./main Hello World! Hello World! 13 This is to test This is to test #define BUFFSIZE 4096 8 int main() int n; char buf[BUFFSIZE]; while( (n = read(STDIN_FILENO, buf, BUFFSIZE))>0) if(write(STDOUT_FILENO, buf,n)!=n) perror("Write error"); //write to stderr sprintf(buf,"%d\n",n); write(STDERR_FILENO, buf, strlen(buf)); if( n < 0) perror("read error"); exit(0);