how do I take a filename and copy it into a new file with a different extension?

This is a discussion on how do I take a filename and copy it into a new file with a different extension? within the C Programming forums, part of the General Programming Boards category; Like I want to make a copy of yar.txt how do I use that filename and add a .cpy to ...

  1. #1
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    how do I take a filename and copy it into a new file with a different extension?

    Like I want to make a copy of yar.txt how do I use that filename and add a .cpy to it?

  2. #2
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    Read this thread on the same topic.

    How do I make a program with two arguments in dos

    Tim S.
    "Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the universe trying to produce bigger and better idiots. So far, the Universe is winning." Rick Cook

  3. #3
    Registered User whiteflags's Avatar
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    Assuming you have two strings, one with the filename, and the other with the new extension, you could always copy both strings into a third string with strncpy().

  4. #4
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    Method one...
    Code:
    char NewName[255] = {0};
    
    strcpy(NewName,OldName);
    strcat(NewName,".cpy");
    
    // result:  filename.txt.cpy
    Method 2...
    Code:
    char NewName[255] = {0};
    char* ptr;
    
    strcpy(NewName,OldName);
    ptr = strchr(NewName,'.');
    strcpy(ptr,".cpy");
    
    // result... filename.txt becomes filename.cpy

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    thanks

  6. #6
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    I am trying it this way:
    Code:
    char NewName[250] = {0};
        char Oldname[250]={argv[1]};
        strcpy(NewName,Oldname);
        strcat(NewName,".cpy");
    but it isn't working, it compiles ok but when run with the filename after the exe as test.txt it just doesn't work

  7. #7
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    That should generate warnings/errors for your compiler. If not, crank up the warning settings.

    Then, you need to strcpy argv[1] into Oldname. Also, you should pick a consistent formatting for variable names. Either capitalize the 'N' in "Name" for NewName and OldName or don't, but be consistent.

  8. #8
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    Can you be a little more specific.
    Do you want to copy the filename or the contents of the file?

  9. #9
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    copy both but make the copy of the file have an extra extension on the end like .cpy

  10. #10
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    You don't need to save argv[1], you can use that throughout your program. Here's another thing you can try, without length limits on the filename. You will need to add file operations and use new_name for the file you write to.

    Code:
    char *new_name = malloc(strlen(argv[1]) + 1 + 4); /* +1 for \0, +4 for .cpy */
    strcpy(new_name, argv[1]);
    strcat(new_name, ".cpy");
    
    puts(new_name);
    
    free(new_name);

  11. #11
    Third Eye Babkockdood's Avatar
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    Some psuedocode:

    Code:
    int main(int argc, char *argv[])
    
    if argv[1] is null, printf usage message
    
    argv[1] will be file to be copied
    
    FILE *in = fopen argv[1], mode "r"
    
    FILE *out = fopen argv[1] with ".cpy" added on, mode "w"
    
    int x;
    while ((x = fgetc(in)) != EOF) {
        fputc(x, out)
    }
    printf("SUCCESS!!!\n");
    Remember: they're called file streams for a reason. When you read a byte from an input stream (or write a byte to an output stream), it will automatically advance you to the next character, so you don't overwrite the last character you wrote, and you don't read the same byte again. This is much more efficient than copying the entire input file into memory, and writing the entire output file from memory.

    Refer to the other posts in this thread for working with strings.
    Quote Originally Posted by The Jargon File
    Microsoft Windows - A thirty-two bit extension and graphical shell to a sixteen-bit patch to an eight-bit operating system originally coded for a four-bit microprocessor which was written by a two-bit company that can't stand one bit of competition.

  12. #12
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    Quote Originally Posted by Once-ler View Post
    I am trying it this way:
    Code:
    char NewName[250] = {0};
        char Oldname[250]={argv[1]};
        strcpy(NewName,Oldname);
        strcat(NewName,".cpy");
    but it isn't working, it compiles ok but when run with the filename after the exe as test.txt it just doesn't work
    This is what happens when you do scoop and poop coding... I gave you an EXAMPLE... not a finished product.

    Code:
    int main ( int argc, char* argv[] )
      {
         char OutputFile[256] = {0};
    
         // part of your program code here
    
        strcpy(OutputFile, argv[1]);
        strcat(outputFile,".cpy");
        fp = fopen(OutputFile,"w");
        if (! fp)
          { 
             printf("Could not open %s",OutputFile);
             exit(-1);
           }
    
        // rest of program here
    
       return 0;
    }
    Get the idea... I gave you a general suggestion... you need to expand and modify it to your needs.
    Last edited by CommonTater; 01-10-2012 at 08:39 PM.

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    thanks

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