Re: [Bug-gnulib] copying file timestamps (was: utimes.m4)

[Bruno Haible]

Paul Eggert wrote:
> copy-file.c prefers utime to utimes, so it should be fine too.
> I don't know of any host that lacks utime and has a broken utimes.

OK, thanks for explaining.

But since utimes() can set the file's times with microsecond resolution,
what is the portable way to _get_ a file's times with more than 1 second
resolution?

glibc with __USE_MISC has

    struct timespec st_atim;            /* Time of last access.  */
    struct timespec st_mtim;            /* Time of last modification.  */
    struct timespec st_ctim;            /* Time of last status change.  */

glibc without __USE_MISC has

    __time_t st_atime;                  /* Time of last access.  */
    unsigned long int st_atimensec;     /* Nscecs of last access.  */
    __time_t st_mtime;                  /* Time of last modification.  */
    unsigned long int st_mtimensec;     /* Nsecs of last modification.  */
    __time_t st_ctime;                  /* Time of last status change.  */
    unsigned long int st_ctimensec;     /* Nsecs of last status change.  */

FreeBSD with __BSD_VISIBLE has

        struct  timespec st_atimespec;  /* time of last access */
        struct  timespec st_mtimespec;  /* time of last data modification */
        struct  timespec st_ctimespec;  /* time of last file status change */

FreeBSD without __BSD_VISIBLE has

        time_t    st_atime;             /* time of last access */
        long      st_atimensec;         /* nsec of last access */
        time_t    st_mtime;             /* time of last data modification */
        long      st_mtimensec;         /* nsec of last data modification */
        time_t    st_ctime;             /* time of last file status change */
        long      st_ctimensec;         /* nsec of last file status change */

Solaris 7 with __EXTENSIONS__ has

        timestruc_t     st_atim;
        timestruc_t     st_mtim;
        timestruc_t     st_ctim;

Solaris 7 without __EXTENSIONS__ has

        _timestruc_t     st_atim;
        _timestruc_t     st_mtim;
        _timestruc_t     st_ctim;

I'd like to use these in copy-file.c. Do you already have an autoconf
macro for this?

> Perhaps we should make utimens a gnulib module. tar will need
> something like it once tar adds support for subsecond timestamps.

Yes, I agree. One module for getting the subsecond timestamp, and one
for setting it, would be perfect.

Bruno