help plz: opening mutiple files in c

This is a discussion on help plz: opening mutiple files in c within the C++ Programming forums, part of the General Programming Boards category; i have a bunch of files to open as 1,2,3......1000 i can open a file as: ifstream indata; indata.open("1"); but ...

  1. #1
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    help plz: opening mutiple files in c

    i have a bunch of files to open as 1,2,3......1000

    i can open a file as:
    ifstream indata;
    indata.open("1");

    but i dont want to open all of them manually,
    is there any way to open like -

    for(int i=1;i<1000;i++)
    indata.open(i);

    plz tell me asap...thanks...

  2. #2
    spurious conceit MK27's Avatar
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    Code:
    map<string,ifstream> filehash;
    ifstream cur;
    for (i=0; i<100; i++) {
        cur.open("name_of_file",ios::in);
        if (cur.fail()) cerr << "Can't open....";
        filehash["name_of_file"] = cur;
    }
    There may be a limit set by your OS on the number of open files one process can have.
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  3. #3
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    the problem is i have to write this statement 1000 times (for 1000 files)
    cur.open("name_of_file",ios::in);

    like cur.open("1",ios::in);
    cur.open("2",ios::in);
    cur.open("3",ios::in);
    ........and so on

    If we write it in a loop:

    for(i=1;i<1000;i++)
    cur.open(i,ios::in);

    it will give error because i is integer & it wants string there.
    If we try to type cast it, it will convert integer value into ascii which we dont want.
    Is there any other solution?

  4. #4
    spurious conceit MK27's Avatar
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    The best way to do this, if all these files are in the same directory, is open the directory -- with opendir() -- read the file names into a vector<string> -- with readdir(), etc -- then you can use that vector in the for loop.

    If you are too lazy for that, tho, and all the files are literally called "1" "2", etc, just create a vector of the filenames:

    Code:
    	vector<string> fnames;
    	int i;
    	char tmp[8];
    	for (i=0;i<100;i++) {
    		sprintf(tmp,"%d",i);
    		fnames.push_back(tmp);
    		cout << fnames[i] <<endl;  // verify
    	}
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

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