Thread: Print text file to the monitor

  1. #1
    Registered User
    Join Date
    May 2017
    Posts
    61

    Print text file to the monitor

    The code is working nice for me.

    But feel free to give me advice.

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #define SIZE 100
    
    
    int main(int argc, char** argv) {
    
    
        FILE *pFile;
        char string[SIZE];
    
    
        if ((pFile = fopen("code.txt", "rt")) == NULL) {
            printf("error");
            return -1;
        }
    
    
        while (fgets(string, sizeof (string), pFile) != NULL) {
            if (printf("%s", string) < 0) {
                puts("Error printf");
                fclose(pFile);
                return -1;
            }
        }
    
        fclose(pFile);
        
        return (EXIT_SUCCESS);
    }
    Last edited by thinkabout; 07-10-2017 at 06:44 AM.

  2. #2
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    Location
    The edge of the known universe
    Posts
    38,175
    Perhaps specify the file to show via command line arguments (argv).
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

  3. #3
    Registered User
    Join Date
    May 2017
    Posts
    61
    Quote Originally Posted by Salem View Post
    Perhaps specify the file to show via command line arguments (argv).
    Code:
        if ((pFile = fopen(argv[1], "rt")) == NULL) {
            printf("%d %s\n", errno, strerror(errno));
            return -1;
        }

  4. #4
    Registered User
    Join Date
    May 2012
    Location
    Arizona, USA
    Posts
    738
    The character 't' in the "mode" argument to the fopen() call is non-standard and has undefined behavior. If you want to open the file in "text" mode, just leave out the 't'.

  5. #5
    Registered User
    Join Date
    Jun 2015
    Posts
    1,643
    Quote Originally Posted by christop View Post
    The character 't' in the "mode" argument to the fopen() call is non-standard and has undefined behavior. If you want to open the file in "text" mode, just leave out the 't'.
    It is not undefined behaviour. System-dependent extra characters are allowed after the standard sequences and are meant to be ignored if not understood. I recall something about being able to set Windows so that the default opening mode was binary, so the text mode flag could be necessary.

  6. #6
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    Location
    The edge of the known universe
    Posts
    38,175
    fopen, _wfopen
    If t or b is not given in mode, the default translation mode is defined by the global variable _fmode. If t or b is prefixed to the argument, the function fails and returns NULL.
    You can't even be sure of a standard non-standard behaviour with M$.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

  7. #7
    Registered User
    Join Date
    May 2012
    Location
    Arizona, USA
    Posts
    738
    Quote Originally Posted by algorism View Post
    It is not undefined behaviour. System-dependent extra characters are allowed after the standard sequences and are meant to be ignored if not understood. I recall something about being able to set Windows so that the default opening mode was binary, so the text mode flag could be necessary.
    Ah, you're right. The C11 (draft) standard says:

    The argument mode points to a string. If the string is one of the following, the file is open in the indicated mode. Otherwise, the behavior is undefined.

    r open text file for reading
    w truncate to zero length or create text file for writing
    a append; open or create text file for writing at end-of-file
    rb open binary file for reading
    wb truncate to zero length or create binary file for writing
    ab append; open or create binary file for writing at end-of-file
    r+ open text file for update (reading and writing)
    w+ truncate to zero length or create text file for update
    a+ append; open or create text file for update, writing at end-of-file
    r+b or rb+ open binary file for update (reading and writing)
    w+b or wb+ truncate to zero length or create binary file for update
    a+b or ab+ append; open or create binary file for update, writing at end-of-file
    but that has a footnote:

    If the string begins with one of the above sequences, the implementation might choose to ignore the remaining characters, or it might use them to select different kinds of a file
    so it's undefined behavior, unless the implementation either supports the trailing characters or chooses to ignore them.

    In any case, unless you need a special mode, and you know your application is going to run on a specific implementation that supports it, then I recommend sticking to one of the standard modes.

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. Output does not print on text file fputc();
    By mohsen in forum C Programming
    Replies: 1
    Last Post: 07-19-2013, 04:10 PM
  2. print the data from 2 text file
    By Wei Yoong in forum C Programming
    Replies: 2
    Last Post: 10-22-2012, 09:18 AM
  3. How to print text from a file to the screen
    By Chrisboggis in forum C Programming
    Replies: 3
    Last Post: 10-24-2009, 04:29 PM
  4. Print a Text File
    By Carliviris in forum C++ Programming
    Replies: 2
    Last Post: 01-15-2007, 12:27 PM
  5. trying to print a line from a text file
    By kryonik in forum C++ Programming
    Replies: 1
    Last Post: 06-06-2006, 09:14 PM

Tags for this Thread