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Description
Bug report
Bug description:
The method tell() returns a lower value than expected. It does not point to the position of the last written byte.
Consider this example:
# appender.py
import sys
file = open(sys.argv[1], 'a+b')
file.seek(0)
file.write(b'56789')
print('offset:', file.tell())$ printf "01234" > myfile
$ python appender.py myfile
offset: 5The value should be 10 instead of 5.
Equivalence in C
/* appender.c */
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
int main(int argc, char **argv){
if (argc!=2){
puts("usage ./test file");
return 1;
}
int fd = open(argv[1], O_RDWR | O_CREAT | O_APPEND, S_IRUSR | S_IWUSR);
lseek(fd, 0, SEEK_SET);
write(fd, "56789", 5);
printf("offset: %ld\n", lseek(fd, 0, SEEK_CUR));
return 0;
}which returns the expected value:
$ ./appender
offset: 10CPython versions tested on:
3.11, 3.12, 3.13
Operating systems tested on:
Linux