source: bootcd/isolinux/syslinux-6.03/core/fs/lib/searchconfig.c

#include <dprintf.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <core.h>
#include <fs.h>

__export char ConfigName[FILENAME_MAX];
__export char config_cwd[FILENAME_MAX];

/*
 * This searches for a specified set of filenames in a specified set
 * of directories.  If found, set the current working directory to
 * match.
 */
int search_dirs(struct com32_filedata *filedata,
                const char *search_directories[],
                const char *filenames[],
                char *realname)
{
    char namebuf[FILENAME_MAX];
    const char *sd, **sdp;
    const char *sf, **sfp;

    for (sdp = search_directories; (sd = *sdp); sdp++) {
        for (sfp = filenames; (sf = *sfp); sfp++) {
            snprintf(namebuf, sizeof namebuf,
                     "%s%s%s",
                     sd, (*sd && sd[strlen(sd)-1] == '/') ? "" : "/",
                     sf);
            if (realpath(realname, namebuf, FILENAME_MAX) == (size_t)-1)
                continue;
            dprintf("Config search: %s\n", realname);
            if (open_file(realname, O_RDONLY, filedata) >= 0) {
                chdir(sd);
                return 0;       /* Got it */
            }
        }
    }

    return -1;
}