From: pjfarley AT banet DOT net (Peter J. Farley III)
Newsgroups: comp.os.msdos.djgpp
Subject: Q: libc fstat: Why is st_ctime < st_atime == st_mtime after fopen?
Date: Tue, 29 Aug 2000 04:46:58 GMT
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I have a small test program (see below) which unlinks a file, uses
fopen to open the file in "wt" mode, and then calls fstat on the
newly-opened file.  The time values in the stat structure have this
relationship to each other immediately after the open, before any
write to the file has occurred:

st_ctime < st_atime == st_mtime

For example, the test program produced this output when I just ran it:

atime=967508974,ctime=967508972,mtime=967508974

On first glance, I would have thought that all these values would be
equal right after an "open for output" on a new file.  If there is a
reason they are not, I would appreciate knowing why.

The test program mirrors perl code that is failing in testing a DJGPP
build of perl-5.6.0, which expects that ctime == mtime unless the
system is Cygwin or Win32 (but makes no exception for DJGPP).  I need
to know if it is intentional or system-related that ctime != mtime in
the DJGPP fstat results, so that the perl test case can be adjusted
appropriately for DJGPP.

Any info or RTFM's appreciated.

------------ teststat.c ----------------------------------
#include <stdio.h>
#include <sys/stat.h>

int main () {
    struct stat mystat;
    FILE *tmp;

    unlink("Opstat.tmp");
    tmp = fopen("Opstat.tmp", "wt");
    fstat(fileno(tmp), &mystat);
    printf("atime=%d,ctime=%d,mtime=%d\n",
        mystat.st_atime, mystat.st_ctime, mystat.st_mtime);
    fprintf(tmp, "Unrelated data\n");
    fclose(tmp);
}
------------ teststat.c ----------------------------------


----------------------------------------------------
Peter J. Farley III (pjfarley AT nospam DOT dorsai DOT org OR
                     pjfarley AT nospam DOT banet DOT net)