Thread: C Programming in UNIX

There are several problems.

1. Your code looks like dog-food. The indentation is awful, and probably hiding your mistakes.

Code:

#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <ctype.h>
//need two pipes and string input 

int main(int argc, char *argv[])
{
  int pipe1[2];
  int pipe2[2];
  char input[100];

  if (pipe(pipe1) == -1) {      // if any issues creating the pipe
    printf("pipe1 failed\n");
    exit(1);
  }

  if (pipe(pipe2) == -1) {      // if any issues creating the pipe
    printf("pipe2 failed\n");
    exit(1);
  }

  scanf("%s", input);
  if (fork() < 0) {
    printf("fork failed\n");
  } else if (fork() == 0) {     //that is child process to convert string to uppercase
    char new[100];              //to save the uppercase string
    //child only read so close writing end
    close(pipe1[1]);
    read(pipe1[0], new, 100);
    int l = strlen(new);
    for (int i = 0; i < l; i++) {
      new[i] = toupper(new[i]);
    }
    close(pipe1[0]);
    close(pipe2[0]);
    write(pipe2[1], new, l + 1);  //length of the string 
    close(pipe2[1]);
    exit(0);
  } else
    (fork() > 0);   //!! WTF is this!?
    {  
    char new[100];
    close(pipe1[0]);

    write(pipe1[1], input, strlen(input) + 1);
    close(pipe1[1]);

    //once that is done child process starts so 
    wait(NULL);
    close(pipe2[1]);
    read(pipe2[0], new, 100);
    printf("new string %s\n", new);
    close(pipe2[0]);
    }
}

2. You're creating more processes than you bargain for.

Code:

  if (fork() < 0) {
    printf("fork failed\n");
  } else if (fork() == 0) {     //that is child process to convert string to uppercase

NO!!!
This does not create one child and tests whether it's parent or child, it creates two children

Code:

pid_t p = fork();
if ( p < 0 } {
} else if ( p == 0 ) {
} else {
}

3. Line 46 -> (fork() > 0); //!! WTF is this!?
else clauses don't have conditions.

4. ISSUE : It only read one word and terminates as soon as reaches a first space/null
Well use fgets to read a whole line, instead of scanf %s, which stops at the first white space.