sane_link.c

[詳解]

/*++
/* NAME
/*  sane_link 3
/* SUMMARY
/*  sanitize link() error returns
/* SYNOPSIS
/*  #include <sane_fsops.h>
/*
/*  int sane_link(from, to)
/*  const char *from;
/*  const char *to;
/* DESCRIPTION
/*  sane_link() implements the link(2) system call, and works
/*  around some errors that are possible with NFS file systems.
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*--*/

/* System library. */

#include "sys_defs.h"
#include <sys/stat.h>
#include <errno.h>
#include <unistd.h>

/* Utility library. */

#include "msg.h"
#include "sane_fsops.h"
#include "warn_stat.h"

/* sane_link - sanitize link() error returns */

int     sane_link(const char *from, const char *to)
{
    const char *myname = "sane_link";
    int     saved_errno;
    struct stat from_st;
    struct stat to_st;

    /*
     * Normal case: link() succeeds.
     */
    if (link(from, to) >= 0)
    return (0);

    /*
     * Woops. Save errno, and see if the error is an NFS artefact. If it is,
     * pretend the error never happened.
     */
    saved_errno = errno;
    if (stat(from, &from_st) >= 0 && stat(to, &to_st) >= 0
    && from_st.st_dev == to_st.st_dev
    && from_st.st_ino == to_st.st_ino) {
    msg_info("%s(%s,%s): worked around spurious NFS error",
         myname, from, to);
    return (0);
    }

    /*
     * Nope, it didn't. Restore errno and report the error.
     */
    errno = saved_errno;
    return (-1);
}