Difference between r and w in fopen

Question

In fopen  myfile    r    what is the difference between the  r   and  w   open mode  I read this       r    Open a text file for reading   w  Open a text file for writing    truncating an an existing file to zero length  or creating the file if it does not exist        r   Open a text file for update  that is  for both reading and   writing    w   Open a text file for update  reading and writing     first truncating       the file to zero length if it exists or creating the file if it does not    exist    I mean the difference is that if I open the file with  w    the file will be erased first

User · Answer

r  The existing file is opened to the beginning for both reading and writing   w  Same as w except both for reading and writing

User · Answer

Both r  and w  can read and write to a file  However  r  doesn t delete the content of the file and doesn t create a new file if such file doesn t exist  whereas w  deletes the content of the file and creates it if it doesn t exist

User · Answer

The main difference is w  truncate the file to zero length if it exists or create a new file if it doesn t  While r  neither deletes the content nor create a new file if it doesn t exist      Try these codes and you will understand      include  lt stdio h gt  int main        FILE  fp      fp   fopen  test txt    w        fprintf fp   This is testing for fprintf    n       fputs  This is testing for fputs    n   fp      fclose fp         and then this     include  lt stdio h gt  int main        FILE  fp      fp   fopen  test txt    w        fclose fp          Then open the file test txt and see the what happens  You will see that all data written by the first program has been erased  Repeat this for r  and see the result  Hope you will understand

User · Answer

This diagram will be faster to read next time  Maybe someone else will find that helpful too  This is clearly explained the difference between

User · Answer

There are 2 differences  unlike r   w  will    create the file if it does not already exist first truncate it  i e   will delete its contents

User · Answer

w    include  lt stdio h gt  int main        FILE  fp     fp   fopen  test txt    w        write and read mode    fprintf fp   This is testing for fprintf    n         rewind fp     rewind    function moves file pointer position to the beginning of the file     char ch     while  ch getc fp    EOF     putchar ch       fclose fp         output  This is testing for fprintf      test txt  This is testing for fprintf        w and r to form w    include  lt stdio h gt  int main        FILE  fp      fp   fopen  test txt    w      only write mode    fprintf fp   This is testing for fprintf    n        fclose fp      fp   fopen  test txt    r       char ch     while  ch getc fp    EOF     putchar ch      fclose fp         output  This is testing for fprintf      test txt  This is testing for fprintf        r   test txt  This is testing for fprintf       include lt stdio h gt  int main         FILE  fp      fp   fopen  test txt    r        read and write mode     char ch      while  ch getc fp    EOF      putchar ch       rewind fp     rewind    function moves file pointer position to the beginning of the file      fprintf fp   This is testing for fprintf again    n        fclose fp       return 0      output  This is testing for fprintf      test txt  This is testing for fprintf again        r and w to form r   test txt  This is testing for fprintf       include lt stdio h gt  int main         FILE  fp      fp   fopen  test txt    r         char ch      while  ch getc fp    EOF      putchar ch       fclose fp        fp fopen  test txt   w        fprintf fp   This is testing for fprintf again    n        fclose fp       return 0      output  This is testing for fprintf      test txt  This is testing for fprintf again        a   test txt  This is testing for fprintf       include lt stdio h gt  int main         FILE  fp      fp   fopen  test txt    a        append and read mode     char ch      while  ch getc fp    EOF      putchar ch       rewind fp     rewind    function moves file pointer position to the beginning of the file      fprintf fp   This is testing for fprintf again    n        fclose fp       return 0      output  This is testing for fprintf      test txt  This is testing for fprintf    This is testing for fprintf again        a and r to form a   test txt  This is testing for fprintf       include lt stdio h gt  int main         FILE  fp      fp   fopen  test txt    a       append and read mode     char ch      while  ch getc fp    EOF      putchar ch       fclose fp       fp fopen  test txt   r        fprintf fp   This is testing for fprintf again    n        fclose fp       return 0      output  This is testing for fprintf      test txt  This is testing for fprintf    This is testing for fprintf again

User · Answer

r   read mode only r    read write mode w   write mode only w    read write mode  if the file already exists override it  empty it    So yes  if the file already exists w  will erase the file and give you an empty file

[c] Difference between r+ and w+ in fopen()

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