Format
#include <stdio.h>
long int ftell(FILE *stream);
off_t ftello(FILE *stream);Language Level: ANSI
Threadsafe: Yes.
Integrated File System Interface: The ftello() function is not available when SYSIFCOPT(*NOIFSIO) is specified on the compilation command.
Description
The ftell() and ftello() functions find the current position of the file associated with stream. For a fixed-length binary file, the value that is returned is an offset relative to the beginning of the stream.
For file in the QSYS library system, the ftell() and ftello() functions return a relative value for fixed-format binary files and an encoded value for other file types. This encoded value must be used in calls to the fseek() and fseeko()functions to positions other than the beginning of the file.
Return Value
The ftell() and ftello() functions return the current file position. On error, ftell() and ftello() return –1, cast to long and off_t respectively, and set errno to a nonzero value.
The value of errno can be set to:
The ftell() and ftello() functions are not supported for files that are opened with type=record.
Example that uses ftell()
This example opens the file mylib/myfile for reading. It reads enough characters to fill half of the buffer and prints out the position in the stream and the buffer.
#include <stdio.h>
#define NUM_ALPHA 26
#define NUM_CHAR 6
int main(void)
{
FILE * stream;
int i;
char ch;
char buffer[NUM_ALPHA];
long position;
if (( stream = fopen("mylib/myfile", "r")) != NULL )
{
/* read into buffer */
for ( i = 0; ( i < NUM_ALPHA/2 ) && ((buffer[i] = fgetc(stream)) != EOF ); ++i )
if (i==NUM_CHAR-1) /* We want to be able to position the */
/* file pointer to the character in */
/* position NUM_CHAR */
position = ftell(stream);
buffer[i] = '\0';
} printf("Current file position is %d\n", position);
printf("Buffer contains: %s\n", buffer);
}Related Information