Message192739
| Author |
christian.heimes |
| Recipients |
christian.heimes, ferringb, georg.brandl, gregory.p.smith, ronaldoussoren, rosslagerwall |
| Date |
2013年07月09日.11:30:59 |
| SpamBayes Score |
-1.0 |
| Marked as misclassified |
Yes |
| Message-id |
<1373369460.33.0.363639251888.issue13788@psf.upfronthosting.co.za> |
| In-reply-to |
| Content |
In case someone is wondering if the approach really reduces the amount of syscalls: yes, it does. readdir() doesn't do a syscall for each entry. On Linux it uses the internal syscall getdents() to fill a buffer of directory entry structs. http://man7.org/linux/man-pages/man2/getdents.2.html
On my system os.listdir() does four syscalls:
$ strace python -c "import os; os.listdir('/home/heimes')"
openat(AT_FDCWD, "/home/heimes", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
getdents(3, /* 381 entries */, 32768) = 12880
getdents(3, /* 0 entries */, 32768) = 0
close(3)
On Linux you can also use /proc/self/fd instead of /proc/YOURPID/fd.
Other operating systems have different APIs to get a list of open FDs. AFAK /dev/fd is static on FreeBSD and Mac OS X:
FreeBSD:
http://www.manualpages.de/FreeBSD/FreeBSD-7.4-RELEASE/man3/kinfo_getfile.3.html
Darwin / Mac OS X:
proc_pidinfo() |
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