File I/O in C-using user input

[yohan610]

i have to build a program where the user enters the required input and output filenames..how do i open such files?

tht is
input_file = fget(.......... ..)

finput =fopen(input_fi le,"rb")

i cannot seem to get the user specified file to open..how do i do this???

also how to i read bit by bit from this input file and save the encrypted bits to an output file???(this is a data encryption program....)

[ilikepython]

i have to build a program where the user enters the required input and output filenames..how do i open such files?

tht is
input_file = fget(.......... ..)

finput =fopen(input_fi le,"rb")

i cannot seem to get the user specified file to open..how do i do this???

also how to i read bit by bit from this input file and save the encrypted bits to an output file???(this is a data encryption program....)

Are you using a FILE * pointer.?:
[code=c]
FILE *fp = NULL;
fp = fopen("text.txt ", "rb");
if (fp == NULL)
{
printf("Could not open file\n");
return 1;
}
[/code]
You can read one character at a time by using fgetc().

[yohan610]

Are you using a FILE * pointer.?:
[code=c]
FILE *fp = NULL;
fp = fopen("text.txt ", "rb");
if (fp == NULL)
{
printf("Could not open file\n");
return 1;
}
[/code]
You can read one character at a time by using fgetc().

here is my complete code

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

FILE *finput, *foutput;

int main()
{
	char input_file[255],output_file[255],keyword[255];
	int seed_val=0,help=0;
	int i = 0;

	printf("\nDo u require help?(Enter '1' or '0')");
	fgets(help,1,stdin);
	if (help == 1);
	{
		printf("\Help");
	}
		
		
	printf("Enter the input file:");
	fgets(input_file,sizeof(input_file),stdin);
	finput = fopen(input_file,"rb");
	for(; i < sizeof(input_file); i++)
		printf("%c", input_file[i]);
	
	if (finput == NULL)
	{
		printf("\nError opening input file,please enter another file:");
		while (finput == NULL)
		{
			printf("\nError opening input file,please enter another file:");
			printf("\nEnter the input file:");
			fgets(input_file,30,stdin);
			finput = fopen(input_file,"r");
		}
	}
	else printf("Input file opened succesfully\n");

	printf("\nEnter the output file:");
	fgets(output_file,30,stdin);
	foutput = fopen(output_file,"w");

	if (foutput == NULL)
	{
		printf("\nError opening output file,please enter another file:");
		while (foutput == NULL)
		{
			printf("\nEnter the output file:");
			fgets(output_file,30,stdin);
			foutput = fopen(output_file,"r");
		}
	}

	printf("\nEnter the keyword:");
	fgets(keyword,30,stdin);

	printf("\nEnter seed generator value:");
	scanf_s("%d",&seed_val);
	
	printf("%s",input_file);


}

it just doesnt seem to work..i hope someone can help me..it always returns the value tht input file is NULL

[ilikepython]

here is my complete code

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

FILE *finput, *foutput;

int main()
{
	char input_file[255],output_file[255],keyword[255];
	int seed_val=0,help=0;
	int i = 0;

	printf("\nDo u require help?(Enter '1' or '0')");
	fgets(help,1,stdin);
	if (help == 1);
	{
		printf("\Help");
	}
		
		
	printf("Enter the input file:");
	fgets(input_file,sizeof(input_file),stdin);
	finput = fopen(input_file,"rb");
	for(; i < sizeof(input_file); i++)
		printf("%c", input_file[i]);
	
	if (finput == NULL)
	{
		printf("\nError opening input file,please enter another file:");
		while (finput == NULL)
		{
			printf("\nError opening input file,please enter another file:");
			printf("\nEnter the input file:");
			fgets(input_file,30,stdin);
			finput = fopen(input_file,"r");
		}
	}
	else printf("Input file opened succesfully\n");

	printf("\nEnter the output file:");
	fgets(output_file,30,stdin);
	foutput = fopen(output_file,"w");

	if (foutput == NULL)
	{
		printf("\nError opening output file,please enter another file:");
		while (foutput == NULL)
		{
			printf("\nEnter the output file:");
			fgets(output_file,30,stdin);
			foutput = fopen(output_file,"r");
		}
	}

	printf("\nEnter the keyword:");
	fgets(keyword,30,stdin);

	printf("\nEnter seed generator value:");
	scanf_s("%d",&seed_val);
	
	printf("%s",input_file);


}

it just doesnt seem to work..i hope someone can help me..it always returns the value tht input file is NULL

You shouldn't really use sizeof and you should remove the newline left by fgets():
[code=c]
printf("Enter the input file:");
fgets(input_fil e, 255, stdin); /* 255; maximum of input_file */
input_file[strlen(input_fi le) - 1] = '\0'; /* remove newline; could be done better */
for(; i < strlen(input_fi le); i++)
printf("%c", input_file[i]);
finput = fopen(input_fil e,"rb");
[/code]
That worked for me.

[yohan610]

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

FILE *finput, *foutput;

int main()
{
	char input_file[255],output_file[255],keyword[255];
	int seed_val=0,help=0;
	int i = 0;

	printf("Enter the input file:");
	fgets(input_file,255,stdin);
	input_file[strlen(input_file-1)] = '\0';

	for (; i < strlen(input_file); i++)
		printf("%c", input_file[i]);

	finput = fopen(input_file,"rb");
		
	if (finput == NULL)
	{
		printf("\nError opening input file,please enter another file:");
		while (finput == NULL)
		{
			printf("\nError opening input file,please enter another file:");
			printf("\nEnter the input file:");
			fgets(input_file,30,stdin);
			fopen_s(&finput,input_file,"r");
		}
	}
	else printf("Input file opened succesfully\n");

	printf("\nEnter the output file:");
	fgets(output_file,30,stdin);
	foutput = fopen(output_file,"w");

	if (foutput == NULL)
	{
		printf("\nError opening output file,please enter another file:");
		while (foutput == NULL)
		{
			printf("\nEnter the output file:");
			fgets(output_file,30,stdin);
			foutput = fopen(output_file,"r");
		}
	}

	printf("\nEnter the keyword:");
	fgets(keyword,30,stdin);

	printf("\nEnter seed generator value:");
	scanf_s("%d",&seed_val);
	
	


}

this is my modified code, but it still says the there is an error in opening the file

[yohan610]

sorry my bad...made a typo..now it works!!!