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ftell(), ftello()

Return the current position of a stream

Synopsis:

#include <stdio.h>

long int ftell( FILE* fp );

off_t ftello( FILE* fp );

Arguments:

fp

The stream that you want to get the current position of.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The ftell() function returns the current position of the stream specified by fp. This position defines the character that will be read or written by the next I/O operation on the file. You can use the value returned by ftell() in a subsequent call to fseek() to restore the file position to a previous value.

The ftello() function is similar to ftell(), except that the position is returned as an off_t.

Returns:

The current position of the file or -1L if an error occurred (errno is set).

Examples:

#include <stdio.h>
#include <stdlib.h>

long filesize( FILE *fp )
{
    long int save_pos;
    long size_of_file;

    /* Save the current position. */
    save_pos = ftell( fp );
    
    /* Jump to the end of the file. */
    fseek( fp, 0L, SEEK_END );
    
    /* Get the end position. */
    size_of_file = ftell( fp );
    
    /* Jump back to the original position. */
    fseek( fp, save_pos, SEEK_SET );

    return( size_of_file );
}

int main( void )
{
    FILE *fp;

    fp = fopen( "file", "r" );

    if( fp != NULL ) {
        printf( "File size=%ld\n", filesize( fp ) );
        fclose( fp );
        
        return EXIT_SUCCESS;
    }
    
    return EXIT_FAILURE;
}

Classification:

ftell() is ANSI, POSIX 1003.1; ftello() is POSIX 1003.1

Safety:
Cancellation point	Yes
Interrupt handler	No
Signal handler	No
Thread	Yes

See also:

errno, fgetpos(), fopen(), fsetpos(), fseek()

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