C Exercises: Encrypt a text file
C File Handling : Exercise-13 with Solution
Write a program in C to encrypt a text file.
Assume that, the content of the file test.txt is : Welcome to w3resource.com.
Sample Solution:
C Code:
#include <stdio.h>
#include <stdlib.h>
void main()
{
char fname[20], ch;
FILE *fpts, *fptt;
printf("\n\n Encrypt a text file :\n");
printf("--------------------------\n");
printf(" Input the name of file to encrypt : ");
scanf("%s",fname);
fpts=fopen(fname, "r");
if(fpts==NULL)
{
printf(" File does not exists or error in opening..!!");
exit(1);
}
fptt=fopen("temp.txt", "w");
if(fptt==NULL)
{
printf(" Error in creation of file temp.txt ..!!");
fclose(fpts);
exit(2);
}
while(1)
{
ch=fgetc(fpts);
if(ch==EOF)
{
break;
}
else
{
ch=ch+100;
fputc(ch, fptt);
}
}
fclose(fpts);
fclose(fptt);
fpts=fopen(fname, "w");
if(fpts==NULL)
{
printf(" File does not exists or error in opening..!!");
exit(3);
}
fptt=fopen("temp.txt", "r");
if(fptt==NULL)
{
printf(" File does not exists or error in opening..!!");
fclose(fpts);
exit(4);
}
while(1)
{
ch=fgetc(fptt);
if(ch==EOF)
{
break;
}
else
{
fputc(ch, fpts);
}
}
printf(" File %s successfully encrypted ..!!\n\n", fname);
fclose(fpts);
fclose(fptt);
}
Sample Output:
Encrypt a text file : -------------------------- Input the name of file to encrypt : test.txt File test.txt successfully encrypted ..!!
If you read the file test.txt you will see the following :
������Ʉ�ӄۗ�������ɒ��ђn
Flowchart:
C Programming Code Editor:
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Previous: Write a program in C to merge two files and write it in a new file.
Next: Write a program in C to decrypt a previously encrypted file file.
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C Programming: Tips of the Day
Static variable inside of a function in C
The scope of variable is where the variable name can be seen. Here, x is visible only inside function foo().
The lifetime of a variable is the period over which it exists. If x were defined without the keyword static, the lifetime would be from the entry into foo() to the return from foo(); so it would be re-initialized to 5 on every call.
The keyword static acts to extend the lifetime of a variable to the lifetime of the programme; e.g. initialization occurs once and once only and then the variable retains its value - whatever it has come to be - over all future calls to foo().
Ref : https://bit.ly/3fOq7XP
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