Scanner class kind of input for C

reader.c

/*
 * reader.c
 * 
 * Copyright 2022 Ashok Shankar Das <ashok@localhost.localdomain>
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02110-1301, USA.
 * 
 * 
 */


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define INITIAL_SIZE 512
/**
 * Read data from stdin and return the input
 */
char* read_input() {
    size_t offset = 0;
    size_t size = INITIAL_SIZE;
    char*  buffer = (char*) malloc(size);
    int ch = -1;

    while ((ch = getchar()) != '\n') {
        if (offset == size - 1) {
            buffer = (char*)realloc(buffer, size *= 2);
            if(buffer == NULL) {
                perror("Call to realloc() failed");
                abort();
            }
        }
        buffer[offset++] = (char)ch;
    }
    return buffer;
}
#define readString read_input
int readInt(char *buffer)
{
	int ret;
	//buffer should not be null
	if(buffer != NULL)
	{
		//now check buffer length should not be 0
		if(strlen(buffer)>0)
		{
			ret= atoi(buffer);
			
			if(buffer!=NULL) free(buffer);
			return(ret);
		}
	}
	fprintf(stderr,"Unable to parse input");
	if(buffer!=NULL) free(buffer);
	exit(EXIT_FAILURE);
}
float readFloat(char *buffer)
{
	float ret;
	//buffer should not be null
	if(buffer != NULL)
	{
		//now check buffer length should not be 0
		if(strlen(buffer)>0)
		{
			ret= atof(buffer);
			
			if(buffer!=NULL) free(buffer);
			return(ret);
		}
	}
	fprintf(stderr,"Unable to parse input");
	if(buffer!=NULL) free(buffer);
	exit(EXIT_FAILURE);
}
double readDouble(char *buffer)
{
	double ret;
	
	char *endpointer;
	//buffer should not be null
	if(buffer != NULL)
	{
		//now check buffer length should not be 0
		if(strlen(buffer)>0)
		{
			ret= strtod(buffer,&endpointer);
			
			if(buffer!=NULL) free(buffer);
			return(ret);
		}
	}
	fprintf(stderr,"Unable to parse input");
	if(buffer!=NULL) free(buffer);
	exit(EXIT_FAILURE);
}
long readLong(char *buffer)
{
	long ret;
	int base =0;
	char *endpointer;
	//buffer should not be null
	if(buffer != NULL)
	{
		//now check buffer length should not be 0
		if(strlen(buffer)>0)
		{
			ret= strtol(buffer,&endpointer,base);
			
			if(buffer!=NULL) free(buffer);
			return(ret);
		}
	}
	fprintf(stderr,"Unable to parse input");
	if(buffer!=NULL) free(buffer);
	exit(EXIT_FAILURE);
}
int main(int argc, char **argv)
{
	printf("Enter a string ");
	char *str = readString();
	printf("%s\n",str);
	
	printf("enter an integer: ");
	int x= readInt(read_input());
	printf("integer x = %d\n",x);
	
	printf("enter a floating point number: ");
	float y= readFloat(read_input());
	printf("float y = %f\n",y);
	
	printf("enter a double: ");
	double z = readDouble(read_input());
	printf("double z = %lf\n",z);
	
	printf("enter a long: ");
	long l = readDouble(read_input());
	printf("long l = %ld\n",l);
	return 0;
}