Programming in C: Unit V: File processing
Detecting the End-of-File
Syntax with Example C Programs
When reading or writing data from files, we often do not know exactly how long the file is. For example, while reading the file, we usually start reading from the beginning and proceed towards the end of the file.
DETECTING
THE END-OF-FILE
When
reading or writing data from files, we often do not know exactly how long the
file is. For example, while reading the file, we usually start reading from the
beginning and proceed towards the end of the file. In C, there are two ways to
detect EOF:
•
While reading the file in text mode, character by air character, the programmer
can compare the character that has been read with the EOF, which is a symbolic
constant defined in stdio.h with a value -1. The following statement, does that
while (1)
{
c = fgetc (fp);
// here c is an int variable
if (c==EOF)
break;
printf("%c", c);
}
•
The other way is to use the standard library function feof() which is defined
in stdio.h. The feof() is used to distinguish between two cases:
When
a stream operation has reached the end of a file
When
the EOF (end of file) error code has returned an error indicator even when the
end of the file has not been reached
The
prototype of feof() can be given as
int feof (FILE *fp);
The
function takes a pointer to the FILE structure of the stream to check as an
argument and returns zero (false) when the end of file has not been reached and
a one (true) if the EOF has been reached. Look at the following:
(The output assumes that a file
Student.DAT already exists and conatins the following data: 1 Aditya 2
Chaitanya 3 Goransh)
#include <stdio.h>
main ()
{
FILE *fp;
char str[80];
fp = fopen("Student.DAT",
"r");
if (fp==NULL)
{
printf("\n The file could not
be opened");
exit (1);
}
/* The loop continues until fp
reaches the end-of-file */
while (!feof (fp)
{
fgets (str, 79, fp);
// Reads 79 bytes at a time
printf("\n %s", str);
}
printf("\n\n File Read. Now
closing the file");
fclose (fp);
return 0;
}
Output
1 Aditya 2 Chaitanya 3 Goransh
Programming in C: Unit V: File processing : Tag: : Syntax with Example C Programs - Detecting the End-of-File
Programming in C: Unit V: File processing
Under Subject
Programming in C
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