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authorHaidong Ji2022-04-15 15:51:30 -0500
committerHaidong Ji2022-04-15 15:51:30 -0500
commit442a49ad5a48d417345959b903ae6a6d32d55759 (patch)
treec7127bb497e5e439018b1915e0136eec2c9cb124 /28_fix_vg_encr/encrypt.c
Great C programming funHEADmaster
Excellent fundamentals and displine training, many tools and techniques exercises: gdb, emacs, valgrind, git
Diffstat (limited to '28_fix_vg_encr/encrypt.c')
-rw-r--r--28_fix_vg_encr/encrypt.c60
1 files changed, 60 insertions, 0 deletions
diff --git a/28_fix_vg_encr/encrypt.c b/28_fix_vg_encr/encrypt.c
new file mode 100644
index 0000000..71b7156
--- /dev/null
+++ b/28_fix_vg_encr/encrypt.c
@@ -0,0 +1,60 @@
+#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;
+}