How to use EOF to run through a text file in C

Question

I have a text file that has strings on each line  I want to increment a number for each line in the text file  but when it reaches the end of the file it obviously needs to stop  I ve tried doing some research on EOF  but couldn t really understand how to use it properly   I m assuming I need a while loop  but I m not sure how to do it

User · Answer

One possible C loop would be    include  lt stdio h gt  int main         int c      while   c   getchar       EOF                              Do something with c  such as check against   n             and increment a line counter                       For now  I would ignore feof and similar functions  Exprience shows that it is far too easy to call it at the wrong time and process something twice in the belief that eof hasn t yet been reached   Pitfall to avoid  using char for the type of c  getchar returns the next character cast to an unsigned char and then to an int  This means that on most  sane  platforms the value of EOF and valid  char  values in c don t overlap so you won t ever accidentally detect EOF for a  normal  char

User · Answer

I would suggest you to use fseek-ftell functions   FILE  stream   fopen  example txt    r     if  stream        puts  I O error  n        return     fseek stream  0  SEEK END   long size   ftell stream   fseek stream  0  SEEK SET    while 1         if ftell stream     size            break                INSERT ROUTINE        fclose stream

User · Answer

How you detect EOF depends on what you re using to read the stream   function                  result on EOF or error                     --------                  ---------------------- fgets                     NULL fscanf                    number of succesful conversions                             less than expected fgetc                     EOF fread                     number of elements read                             less than expected   Check the result of the input call for the appropriate condition above  then call feof   to determine if the result was due to hitting EOF or some other error     Using fgets      char buffer BUFFER SIZE    while  fgets buffer  sizeof buffer  stream     NULL           process buffer     if  feof stream            hit end of file     else          some other error interrupted the read      Using fscanf     char buffer BUFFER SIZE   while  fscanf stream    s   buffer     1     expect 1 successful conversion        process buffer   if  feof stream           hit end of file   else        some other error interrupted the read     Using fgetc     int c  while   c   fgetc stream      EOF         process c   if  feof stream          hit end of file   else        some other error interrupted the read     Using fread     char buffer BUFFER SIZE   while  fread buffer  sizeof buffer  1  stream     1     expecting 1                                                          element of size                                                         BUFFER SIZE         process buffer   if  feof stream          hit end of file   else        some other error interrupted read     Note that the form is the same for all of them  check the result of the read operation  if it failed  then check for EOF   You ll see a lot of examples like   while  feof stream       fscanf stream    s   buffer             This form doesn t work the way people think it does  because feof   won t return true until after you ve attempted to read past the end of the file   As a result  the loop executes one time too many  which may or may not cause you some grief

User · Answer

You should check the EOF after reading from file   fscanf s                      read from file while condition               check EOF      fscanf s                  read from file

[c] How to use EOF to run through a text file in C?

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