Question

I have a program that encrypts files, but adds the extension “.safe” to the end. So the end result is something like “file.txt.safe”

When I go to decrypt the file, the user enters the file name again: “file.txt.safe” which is saved to a char. Now I want to remove “.safe” and rename the file to its original name.

I have tried the following, but nothing seems to happen and there are no errors.

Decrypt (myFile); //decrypts myFile

char * tmp = myFile;
char * newFile;
newFile = strstr (tmp,".safe");  //search tmp for ".safe"
strncpy (newFile,"",5);   //replace .safe with ""

rename (myFile, newFile);

I’m sure I’m missing something obvious, but if this approach doesn’t work, I’m looking for any simple method.

Edited to add:
(copied by moderator from poster’s response to K-ballo)

Thanks everyone. I took the std::string approach and found this to work:

Decrypt(myFile); 
string str = myFile; 
size_t pos = str.find(".safe"); 
str.replace(pos,5,""); 
rename(myFile, str.c_str());

Answer 1

For what you want to do, simply changing the strncpy line to this will work:

*newFile = '\0';

This would still have problems if the filename contains an early .safe (like in file.safest.txt.safe), or if it does not contain the substring .safe at all. You would be better of searching from the end of the array, and making sure you do find something.

This seems like a better approach (although in C++ it would be better to just go with std::string):

char* filename = ...;
size_t filename_length = strlen( filename );
int safe_ext_pos = filename_length - 5; // 5 == length of ".safe"
if( safe_ext_pos > 0 && strcmp( ".safe", filename + safe_ext_pos ) == 0 )
    filename[ safe_ext_pos ] = '\0';

This is the std::string version of the code:

std::string filename = ...;
int safe_ext_pos = filename.length() - 5; // 5 == length of ".safe"
if( safe_ext_pos > 0 && filename.compare( safe_ext_pos, 5, ".safe" ) == 0 )
    filename.erase( safe_ext_pos );