Detecting EOF in C

Question

I am using the following C code to take input from user until EOF occurs  but problem is this code is not working  it terminates after taking first input  Can anyone tell me whats wrong with this code  Thanks in advance   float input   printf  Input No      scanf   f    amp input    while  EOF        printf  Output   f   input       printf  Input No          scanf   f    amp input

User · Answer

while scanf   d  d  a b   EOF       do

User · Answer

EOF is a constant in C  You are not checking the actual file for EOF  You need to do something like this  while  feof stdin     Here is the documentation to feof  You can also check the return value of scanf  It returns the number of successfully converted items  or EOF if it reaches the end of the file

User · Answer

as a starting point you could try replacing  while  EOF    with  while  feof stdin

User · Answer

Another issue is that you re reading with scanf   f    amp input   only   If the user types something that can t be interpreted as a C floating-point number  like  pi   the scanf   call will not assign anything to input  and won t progress from there   This means it would attempt to keep reading  pi   and failing   Given the change to while  feof stdin   which other posters are correctly recommending  if you typed  pi  in there would be an endless loop of printing out the former value of input and printing the prompt  but the program would never process any new input   scanf   returns the number of assignments to input variables it made   If it made no assignment  that means it didn t find a floating-point number  and you should read through more input with something like char string 100  scanf   99s   string     This will remove the next string from the input stream  up to 99 characters  anyway - the extra char is for the null terminator on the string    You know  this is reminding me of all the reasons I hate scanf    and why I use fgets   instead and then maybe parse it using sscanf

User · Answer

You want to check the result of scanf   to make sure there was a successful conversion  if there wasn t  then one of three things is true    scanf   is choking on a character that isn t valid for the  f conversion specifier  i e   something that isn t a digit  dot   e   or  E    scanf   has detected EOF  scanf   has detected an error on reading stdin      Example   int moreData   1      printf  Input no      fflush stdout          Loop while moreData is true     while  moreData      errno   0    int itemsRead   scanf   f    amp input     if  itemsRead    1          printf  Output   f n   input       printf  Input no          fflush stdout         else         if  feof stdin               printf  Hit EOF on stdin  exiting n          moreData   0            else if  ferror stdin                            I  think  scanf   sets errno  if not  replace          the line below with a regular printf   and          a generic  read error  message                  perror  error during read          moreData   0            else             printf  Bad character stuck in input stream  clearing to end of line n          while  getchar        n                empty loop          printf  Input no            fflush stdout

User · Answer

EOF is just a macro with a value  usually -1   You have to test something against EOF  such as the result of a getchar   call   One way to test for the end of a stream is with the feof function   if  feof stdin     Note  that the  end of stream  state will only be set after a failed read   In your example you should probably check the return value of scanf and if this indicates that no fields were read  then check for end-of-file

[c] Detecting EOF in C

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