APUE中fcntl.h的使用及O_SYNC在Mac与Ubuntu下的测试

tree ch3
ch3
├── makefile.sync
├── mycat.c
├── set_fl.c
├── set_fl.h
├── sync.c
└── test

#include "../apue.h" #define BUFFSIZE 4096 int main(void)
{
int n;
char buf[BUFFSIZE];
// set_fl(STDOUT_FILENO, O_SYNC); for O_SYNC
while ((n = read(STDIN_FILENO, buf, BUFFSIZE)) > )
if (write(STDOUT_FILENO, buf, n) != n)
err_sys("write error"); if (n < )
err_sys("read error"); exit();
}

#ifndef SET_FL
#define SET_FLvoid
set_fl(int fd, int flags);
/* flags are file status flags to turn on */void
clr_fl(int fd, int flags);
/* flags are file status flags to turn off */#endif

#include <fcntl.h>
#include "set_fl.h"void set_fl(int fd, int flags)
/* flags are file status flags to turn on */
{
int val; if ((val = fcntl(fd, F_GETFL, )) < )
err_sys("fcntl F_GETFL error"); val |= flags; /* turn on flags */ if (fcntl(fd, F_SETFL, val) < )
err_sys("fcntl F_SETFL error");
}

sync: sync.o set_fl.o
gcc -o sync sync.o set_fl.oset_fl.o: set_fl.c
gcc -c set_fl.c

dd if=/dev/zero of=./test bs= count=
+ records in
+ records out
bytes (1.0 GB) copied, 11.1418 s, 94.1 MB/smake -f makefile.syncgcc mycat.c

time ./a.out < test >./dup.buf
real 0m9.965s
user 0m0.014s
sys 0m1.453stime ./sync < test >./dup.sync
real 0m10.355s
user 0m0.025s
sys 0m1.350s

time ./a.out < test >/dev/null
./a.out < test > /dev/null .10s user .17s system % cpu 2.079 totaltime ./sync < test >/dev/null
./sync < test > /dev/null .10s user .20s system % cpu 2.070 totaltime ./sync < test >./dup.sync
./sync < test > ./dup.sync .27s user .79s system % cpu 53.369 totaltime ./a.out < test >./dup.buf
./a.out < test > ./dup.buf .11s user .06s system % cpu 5.955 total