fileflags.c

UNIX高级环境编程（第二版）文件系统部分的程序

#include    <sys/types.h>
#include    <fcntl.h>
#include    "ourhdr.h"

int
main(int argc, char *argv[])
{
    int        accmode, val;

    if (argc != 2)
        err_quit("usage: a.out <descriptor#>");

    if ( (val = fcntl(atoi(argv[1]), F_GETFL, 0)) < 0)
        err_sys("fcntl error for fd %d", atoi(argv[1]));

    accmode = val & O_ACCMODE;
    if      (accmode == O_RDONLY)    printf("read only");
    else if (accmode == O_WRONLY)    printf("write only");
    else if (accmode == O_RDWR)        printf("read write");
    else err_dump("unknown access mode");

    if (val & O_APPEND)            printf(", append");
    if (val & O_NONBLOCK)        printf(", nonblocking");
#if    !defined(_POSIX_SOURCE) && defined(O_SYNC)
    if (val & O_SYNC)            printf(", synchronous writes");
#endif
    putchar('\n');
    exit(0);
}