1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
|
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
void encrypt(FILE * f, int key, FILE * outfile){
char * line=NULL;
size_t sz=0;
while (getline(&line,&sz, f) >= 0) {
char * ptr = line;
while (*ptr != '\0') {
int c = *ptr;
if (isalpha(c)) {
c = tolower(c);
c -= 'a';
c += key;
c %= 26;
c += 'a';
}
*ptr = c;
ptr++;
}
fprintf(outfile, "%s", line);
}
free(line);
}
int main(int argc, char ** argv) {
if (argc != 3) {
fprintf(stderr,"Usage: encrypt key inputFileName\n");
return EXIT_FAILURE;
}
int key = atoi(argv[1]);
if (key == 0) {
fprintf(stderr,"Invalid key (%s): must be a non-zero integer\n", argv[1]);
return EXIT_FAILURE;
}
FILE * f = fopen(argv[2], "r");
if (f == NULL) {
perror("Could not open file");
return EXIT_FAILURE;
}
//outfileNAme is argv[2] + ".txt", so add 4 to its length.
char * outFileName = malloc((strlen(argv[2]) + 5) * sizeof(*outFileName));
strcpy(outFileName, argv[2]);
strcat(outFileName, ".enc");
FILE * outFile = fopen(outFileName, "w");
encrypt(f,key, outFile);
if (fclose(outFile) != 0) {
perror("Failed to close the input file!");
return EXIT_FAILURE;
}
if (fclose(f) != 0) {
perror("Failed to close the input file!");
return EXIT_FAILURE;
}
free(outFileName);
return EXIT_SUCCESS;
}
|
