ftell is a standard C library function which returns the current offset in a file or stream in relation to the first byte.
Questions tagged [ftell]
70 questions
46
votes
1 answer
ftell on a file descriptor?
Is there a way to do what ftell() does (return the current position in the file) on a raw file descriptor instead of a FILE*? I think there ought to be, since you can seek on a raw file descriptor using lseek().
I know I could use fdopen() to create…
HighCommander4
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20
votes
4 answers
Why is fwrite writing more than I tell it to?
FILE *out=fopen64("text.txt","w+");
unsigned int write;
char *outbuf=new char[write];
//fill outbuf
printf("%i\n",ftello64(out));
fwrite(outbuf,sizeof(char),write,out);
printf("%i\n",write);
printf("%i\n",ftello64(out));
output:
0
25755
25868
what…
zacaj
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18
votes
4 answers
the output of ftell in php function
Here is my code:
showkey
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14
votes
4 answers
ftell at a position past 2GB
On a 32-bit system, what does ftell return if the current position indicator of a file opened in binary mode is past the 2GB point? In the C99 standard, is this undefined behavior since ftell must return a long int (maximum value being 2**31-1)?
Vilhelm Gray
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14
votes
1 answer
ftello/fseeko vs fgetpos/fsetpos
What is the difference between ftello/fseeko and fgetpos/fsetpos? Both seem to be file pointer getting/setting functions that use opaque offset types to sometimes allow 64 bit offsets.
Are they supported on different platforms or by different…
Jeremy Salwen
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8
votes
1 answer
why ftell( stdin ) causes illegal seek error
The following code outputs "Illegal seek":
#include
#include
#include
int main() {
errno = 0;
getchar();
getchar();
getchar();
ftell( stdin );
printf( "%s\n", strerror(errno) );
}
This occurs…
Jim
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8
votes
4 answers
End of FILE* pointer is not equal to size of written data
Very simply put, I have the following code snippet:
FILE* test = fopen("C:\\core.u", "w");
printf("Filepointer at: %d\n", ftell(test));
fwrite(data, size, 1, test);
printf("Written: %d bytes.\n", size);
fseek(test, 0, SEEK_END);
printf("Filepointer…
Daniel
6
votes
0 answers
Streaming HTML5 large (>2GB) videos with PHP
Ok, so basically I'm working on a project where I need to stream MP4 videos from a hidden source.
As most of people in this forum with this problem, I've used a solution derived from:…
Inigo EC
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5
votes
4 answers
Are there cases where fseek/ftell can give the wrong file size?
In C or C++, the following can be used to return a file size:
const unsigned long long at_beg = (unsigned long long) ftell(filePtr);
fseek(filePtr, 0, SEEK_END);
const unsigned long long at_end = (unsigned long long) ftell(filePtr);
const unsigned…
Alex Reynolds
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5
votes
2 answers
ftello() and fseeko() android build errors
I am trying to build Android L for 64-bit architecture.
My code goes like:
#if (HAS_LARGE_FILE_SUPPORT)
#define _FILE_OFFSET_BITS 64 //Defined in header file
/*Some File operations*/
#if HAS_LARGE_FILE_SUPPORT
return fseeko(iFile, offset,…
Android_Noob
- 51
- 2
4
votes
2 answers
initial value of file pointer position returned by ftell() in append mode
I was looking at SO post fseek does not work when file is opened in "a" (append) mode and I got a doubt regarding initial value of file pointer returned by ftell() when we open the file in "a" mode.
I tried below code with file1.txt containing data…
Rajesh
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4
votes
1 answer
Why does ftell skips some positions in the file?
I have a text file named myfile.txt which reads:
line 1
l
My code:
#include
int main(){
FILE *f = fopen("myfile.txt","r");
if(f==NULL){
FILE *fp=fopen("myfile.txt","w");
fclose(fp);
f =…
Chaitanya Vaishampayan
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4
votes
1 answer
Get position for file descriptor in Python
Say, I have a raw numeric file descriptor and I need to get the current position in file based on it.
import os, psutil
# some code that works with file
lp = lib.open('/path/to/file')
p = psutil.Process(os.getpid())
fd = p.get_open_files()[0].fd …
VisioN
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3
votes
2 answers
ftell/fseek fail when near end of file
Reading a text file (which happens to be a PDS Member FB 80)
hFile = fopen(filename,"r");
and have reached up to the point in the file where there is only an empty line left.
FilePos = ftell(hFile);
Then read the last line, which only contains a…
Morag Hughson
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3
votes
1 answer
'correct' semantics for ftell() when used on a memory stream
Can anyone explain the 'correct' semantics for ftell() when used on a memory stream.
Given the following program:
#include
#include
#include
int main(void)
{
puts (gnu_get_libc_version ());
size_t…
Bruce Adams
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