c++ – Reading file content changes


Some program constantly appends a certain number of lines to the Nth number of files. I need to check in a loop whether the file has changed, and if something has been added to it, then read this information. All files have the usual .txt extension. Is there already a ready-made solution in the qt framework? so to speak "out of the box".


There is a tail bike from GNU core utilities .

# dpkg -S  `which tail`
coreutils: /usr/bin/tail

You can run tail -F /var/log/*.log , the -F flag tells the utility to watch for changes.

Thus your problem is solved.

Raw tail on c : http://git.savannah.gnu.org/cgit/coreutils.git/tree/src/tail.c

Nightmarish of course, but only 2400 lines.

2234 int main (int argc, char **argv) {

headers (headers) are filled there, then on the line

2328 for (i = 0; i < n_files; i++) ok &= tail_file (&F[i], n_units);

a matryoshka from tails is launched on files that are already in the headers.

1885 static bool tail_file (struct File_spec *f, uintmax_t n_units) {

inside, just tail() is called

1871 static bool tail (const char *filename, int fd, uintmax_t n_units, uintmax_t *read_pos)

tail_lines() is called there

1809 static bool tail_lines (const char *pretty_filename, int fd, uintmax_t n_lines, uintmax_t *read_pos)

And further there simply lseek-ami pieces are extended… In general, can help.

As a last resort, you can run tail -F {Ваш,Список,Файлов} as a subprocess, and pipe from it…

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