pathalloc.c

unix环境高级编程的源代码

#include    <errno.h>
#include    <limits.h>
#include    "ourhdr.h"

#ifdef    PATH_MAX
static int    pathmax = PATH_MAX;
#else
static int    pathmax = 0;
#endif

#define    PATH_MAX_GUESS    1024    /* if PATH_MAX is indeterminate */
                        /* we're not guaranteed this is adequate */
char *
path_alloc(int *size)
                /* also return allocated size, if nonnull */
{
    char    *ptr;

    if (pathmax == 0) {        /* first time through */
        errno = 0;
        if ( (pathmax = pathconf("/", _PC_PATH_MAX)) < 0) {
            if (errno == 0)
                pathmax = PATH_MAX_GUESS;    /* it's indeterminate */
            else
                err_sys("pathconf error for _PC_PATH_MAX");
        } else
            pathmax++;        /* add one since it's relative to root */
    }

    if ( (ptr = malloc(pathmax + 1)) == NULL)
        err_sys("malloc error for pathname");

    if (size != NULL)
        *size = pathmax + 1;
    return(ptr);
}