Write a program using command line arguments to search for a word in a file and replace it with the specified word. The usage of the program is shown below.

C> change <old word> <new word> <filename> 

Ans:

#include<stdio.h>
#include<conio.h>
#include<string.h>
#include<stdlib.h>

#define EndOfWord word[i] == ' ' || word[i] == ',' \
|| word[i] == '\n' || word[i] == '.'

int main(int ac, char *av[])
{
	FILE *fp, *temp;
	int i, j;
	char word[10], ch;
	if (ac != 4)
	{
		puts("Wrong number of arguements\n.");
		printf("Write like this : ");
		printf("\"change\" \"old_word\"");
		printf("\"new_word\" \"file_name\"\n");
		exit(1);
	}
	fp = fopen(av[3], "r");
	temp = fopen("temp.txt", "w");
	if (fp == NULL)
	{
		perror("Error : ");
		exit(1);
	}
	for (i = 0; (word[i] = fgetc(fp)) != EOF; i++)
	{
		if (EndOfWord)
		{
			ch = word[i];
			word[i] = '\0';
			if (!strcmp(av[1], word))
				fputs(av[2], temp);
			else
				fputs(word, temp);
			fputc(ch, temp);
			i = -1;
		}
	}
	fclose(fp);
	fclose(temp);
	remove(av[3]);
	rename("temp.txt", av[3]);
	return 0;
}