C99 input from pipe ouput stdout

pipe.c

#include <unistd.h>

/**
 * Read input char by char and ouput it.
*/
int main(int argc, char* argv[]){
    int read_status = 1;
    while(read_status){
        char c;
        read_status = read(STDIN_FILENO, &c, 1);
        // eventually do things
        write(STDOUT_FILENO, &c, 1);
    }
    return 0;
}

echo "Hello world !" | ./a.out

pipe.c Using stdio hight level primitives

#include <stdio.h>

/**
 * Read input char by char and ouput it.
*/
int main(int argc, char* argv[]){
    char c;
    do{
        c = getc(stdin);
        //do things ?
        printf("%c", c);
    }while(c != '\0' && c != '\n');
    return 0;
}

pipe.c Storing input on allocated memory

#include <stdio.h> //printf getc
#include <stdlib.h> //alloc

/**
 * Read input char by char and ouput it.
*/
int main(int argc, char* argv[]){

    char *input = malloc(sizeof(char));
    *input = '\0';
    short unsigned int input_size = 1;
    
    char c;
    do{
        c = getc(stdin);

        input = realloc(input, (input_size+1)*sizeof(char));
        *(input+(input_size-1)) = c;
        *(input+(input_size)) = '\0';
        input_size++;
        
    }while(c != '\0' && c != '\n');
    input_size-=2;
    input = realloc(input, (input_size)*sizeof(char));
    *(input+(input_size)) = '\0';

    printf("string is : [%s] size : %d\n", input, input_size);

    free(input);
    input = NULL;

    return EXIT_SUCCESS;
}

pipe.c With memory allocation in a proper function

#include <stdio.h>  // printf getchar
#include <stdlib.h> //alloc

/* Read input from stdin return the input size
 * allocate the input string buffer. */
int getPipeInput(char **input){
    *input = malloc(sizeof(char));
    (*input)[0] = '\0';
    short unsigned int input_size = 1;
    
    char c;
    do{
        c = getchar();

        *input = realloc((*input), (input_size+1)*sizeof(char));
        (*input)[input_size-1] = c;
        (*input)[input_size] = '\0';
        input_size++;
        
    }while(c != '\0' && c != '\n');
    input_size-=2;
    *input = realloc(*input, (input_size+1)*sizeof(char));
    (*input)[input_size] = '\0';

    return input_size;
}

int main(int argc, char **argv){

    char *in;
    int size = getPipeInput(&in);
    printf("[%s] => %d\n", in, size);

    free(in);
    in = NULL;

    // Exit success
    return (EXIT_SUCCESS);
}