Determine if input is file or directory

This is a discussion on Determine if input is file or directory within the C++ Programming forums, part of the General Programming Boards category; Hi: How can I determine whether an input string refers to a file or a directory? For example: input is ...

  1. #1
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    Determine if input is file or directory

    Hi:

    How can I determine whether an input string refers to a file or a directory?

    For example: input is /internet/test

    Is this a file or a directory? Is there a way to determine this using C++?

    Thanks.
    -Zack

  2. #2
    Devil's Advocate SlyMaelstrom's Avatar
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    Check the string for slashes or backslashes.
    Code:
    std::string input;
    /* User Entry */
    if(input.find("/") == std::string::npos && input.find("\\") == std::string::npos) /* File is in the current directory */
    else /* File is in another directory */
    Last edited by SlyMaelstrom; 06-26-2006 at 02:30 PM.
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  3. #3
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    You can use one of the stat() function on it and find out the type that way. For more info: http://www.die.net/doc/linux/man/man2/stat.2.html
    If you understand what you're doing, you're not learning anything.

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    Quote Originally Posted by SlyMaelstrom
    Check the string for slashes or backslashes.
    I'm sorry, but I don't quite understand. In Unix, the "test" could be a file or a directory. Assuming this is user-inputted, how can I (or the program) determine?

    Thanks.
    -Zack

  5. #5
    Devil's Advocate SlyMaelstrom's Avatar
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    Ah I understand, I wasn't thinking clearly. Try itsme's suggestion.

    v Same goes to you down there v
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  6. #6
    Code Goddess Prelude's Avatar
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    >Check the string for slashes or backslashes.
    How does that work? Let's say I have "/mydir/something", how do you know what "something" is when it could be either a directory or a file and the string contains slashes? There's no way to determine such a thing in every case based solely on the contents of the path.
    My best code is written with the delete key.

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    Quote Originally Posted by itsme86
    You can use one of the stat() function on it and find out the type that way. For more info: http://www.die.net/doc/linux/man/man2/stat.2.html
    Thanks for the suggestion. Is there a way to do this on Windows as well? I understand that most Windows files will have an extension, but in a mixed environment, there really can't be a guarantee .
    -Zack

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    Quote Originally Posted by SlyMaelstrom
    Ah I understand, I wasn't thinking clearly. Try itsme's suggestion.

    v Same goes to you down there v
    Thanks anyway, bud .
    -Zack

  9. #9
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    I've used stat() in Windows with several different compilers. I know it works for sure with Dev-C++:
    Code:
    #include <stdio.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    
    int main(void)
    {
      struct stat st;
    
      if(stat("C:\\", &st) == -1)
        puts("Error!");
      else
        printf("C:\\ is%s a directory!\n", S_ISDIR(st.st_mode) ? "" : " not");
    
      if(stat("C:\\io.sys", &st) == -1)
        puts("Error!");
      else
        printf("C:\\io.sys is%s a directory!\n", S_ISDIR(st.st_mode) ? "" : " not");
    
      return 0;
    }
    My output:
    C:\ is a directory!
    C:\io.sys is not a directory!
    If you understand what you're doing, you're not learning anything.

  10. #10
    Gawking at stupidity
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    Oops, sorry. Forgot this was the C++ side of things. Maybe someone can C++ify it for you.
    If you understand what you're doing, you're not learning anything.

  11. #11
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    Quote Originally Posted by itsme86
    Oops, sorry. Forgot this was the C++ side of things. Maybe someone can C++ify it for you.
    Nah, it's cool. I'm glad to learn anyway .
    -Zack

  12. #12
    Registered User whiteflags's Avatar
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    Code:
    #include <fstream>
    
    ofstream fout;
    fout.open("/internet/test", ios::out);
    I don't think ofstream creates files that don't exist, so it should be okay.

    If test is a directory this function will fail, so it's merely important to check the state of the stream after you open it. Most operating systems can handle files without extentions these days, so it's possible that it will work if "test" exists as a datafile.
    Last edited by whiteflags; 06-26-2006 at 03:49 PM.

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    Yes, ofstream will create a file that doesn't exist. That also might fail if the file is read-only.

    Boost has a file system library that might also help with this if stat isn't enough.

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    Thanks all. The stats thing worked with Borland 5.5 .
    -Zack

  15. #15
    semi-colon generator ChaosEngine's Avatar
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    as Daved said
    >> Boost has a file system library that might also help with this if stat isn't enough.

    Code:
    #include "boost/filesystem/operations.hpp" // includes boost/filesystem/path.hpp
    #include "boost/filesystem/fstream.hpp"    // ditto
    #include <iostream>                        // for std::cout
    using boost::filesystem;                   // for ease of tutorial presentation;
    
    path my_path( "/internet/test" );
    if (is_directory(my_path))
    {
        std::cout << "it's a directory!" << std::endl;
    }
    what could be simpler?

    edit: oh and it's portable too!
    Last edited by ChaosEngine; 06-26-2006 at 06:15 PM.
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