pathconf.c

unix环境高级编程的源代码

#include    <sys/types.h>
#include    <sys/param.h>
#include    <sys/stat.h>
#include    <errno.h>
#include    <limits.h>
#include    <unistd.h>

static struct stat    statbuf;

/* We don't check that the file for _PC_MAX_CANON really refers to a
 * terminal device, and so on.  POSIX.1 says that "it is unspecified
 * whether an implementation supports an association of the variable
 * name with the specified file."  Also, things like PATH_MAX aren't
 * correct if the specified file is really an SVR4 file on a "s5"
 * filesystem that has been NFS mounted ...  To check for these
 * details really requires that this code be in the kernel.
 */

static long
_do_pathconf(int name)
{
    switch (name) {
    case _PC_LINK_MAX:    return(LINK_MAX);
    case _PC_MAX_CANON:    return(MAX_CANON);
    case _PC_MAX_INPUT:    return(MAX_INPUT);
    case _PC_NAME_MAX:    return(NAME_MAX);
    case _PC_PATH_MAX:    return(PATH_MAX);
    case _PC_PIPE_BUF:    return(PIPE_BUF);
    case _PC_VDISABLE:    return(_POSIX_VDISABLE);

    case _PC_CHOWN_RESTRICTED:
#ifdef    _POSIX_CHOWN_RESTRICTED    /* always true for BSD */
        return(1);
#else
        return(-1);
#endif

    case _PC_NO_TRUNC:
#ifdef    _POSIX_NO_TRUNC        /* always true for BSD */
        return(1);
#else
        return(-1);
#endif

    default:    
        errno = EINVAL;
        return(-1);
    }
}

long
pathconf(const char *path, int name)
{
    if (stat(path, &statbuf) < 0)
        return(-1);    /* stat sets errno */
    return(_do_pathconf(name));
}

long
fpathconf(int fd, int name)
{
    if (fstat(fd, &statbuf) < 0)
        return(-1);    /* stat sets errno */
    return(_do_pathconf(name));
}