posix: always seek to EOF when opening a file in append mode Python 3 already does this, so skip it there. Consider the program: #include <stdio.h> int main() { FILE *f = fopen("narf", "w"); fprintf(f, "narf\n"); fclose(f); f = fopen("narf", "a"); printf("%ld\n", ftell(f)); fprintf(f, "troz\n"); printf("%ld\n", ftell(f)); return 0; } on macOS, FreeBSD, and Linux with glibc, this program prints 5 10 but on musl libc (Alpine Linux and probably others) this prints 0 10 By my reading of https://pubs.opengroup.org/onlinepubs/009695399/functions/fopen.html this is technically correct, specifically: > Opening a file with append mode (a as the first character in the > mode argument) shall cause all subsequent writes to the file to be > forced to the then current end-of-file, regardless of intervening > calls to fseek(). in other words, the file position doesn't really matter in append-mode files, and we can't depend on it being at all meaningful unless we perform a seek() before tell() after open(..., 'a'). Experimentally after a .write() we can do a .tell() and it'll always be reasonable, but I'm unclear from reading the specification if that's a smart thing to rely on. This matches what we do on Windows and what Python 3 does for free, so let's just be consistent. Thanks to Yuya for the idea.

     1

#!/usr/bin/env python

     2

#

     3

# An example hgweb CGI script, edit as necessary

     4

# See also https://mercurial-scm.org/wiki/PublishingRepositories

     5

     6

# Path to repo or hgweb config to serve (see 'hg help hgweb')

     7

config = "/path/to/repo/or/config"

     8

     9

# Uncomment and adjust if Mercurial is not installed system-wide

    10

# (consult "installed modules" path from 'hg debuginstall'):

    11

#import sys; sys.path.insert(0, "/path/to/python/lib")

    12

    13

# Uncomment to send python tracebacks to the browser if an error occurs:

    14

#import cgitb; cgitb.enable()

    15

    16

from mercurial import demandimport; demandimport.enable()

    17

from mercurial.hgweb import hgweb, wsgicgi

    18

application = hgweb(config)

    19

wsgicgi.launch(application)