fsPromises.access(path[, mode])
path
<string> | <Buffer> | <URL>mode
<integer> 默认值:fs.constants.F_OK
- 返回: <Promise> 成功时将使用
undefined
履行。
测试用户对 path
指定的文件或目录的权限。
mode
参数是可选的整数,指定要执行的可访问性检查。
mode
应该是值 fs.constants.F_OK
或由 fs.constants.R_OK
、fs.constants.W_OK
和 fs.constants.X_OK
中的任何一个(例如 fs.constants.W_OK | fs.constants.R_OK
)的按位或组成的掩码。
查看文件访问的常量以获取可能的 mode
值。
如果可访问性检查成功,则不带值解决 promise。
如果任何可访问性检查失败,则使用 <Error> 对象拒绝 promise。
以下示例检查当前进程是否可以读写文件 /etc/passwd
。
import { access, constants } from 'node:fs/promises';
try {
await access('/etc/passwd', constants.R_OK | constants.W_OK);
console.log('can access');
} catch {
console.error('cannot access');
}
不建议在调用 fsPromises.open()
之前使用 fsPromises.access()
检查文件的可访问性。
这样做会引入竞争条件,因为其他进程可能会在两次调用之间更改文件的状态。
而是,用户代码应直接打开/读取/写入文件,并处理无法访问文件时引发的错误。
path
<string> | <Buffer> | <URL>mode
<integer> Default:fs.constants.F_OK
- Returns: <Promise> Fulfills with
undefined
upon success.
Tests a user's permissions for the file or directory specified by path
.
The mode
argument is an optional integer that specifies the accessibility
checks to be performed. mode
should be either the value fs.constants.F_OK
or a mask consisting of the bitwise OR of any of fs.constants.R_OK
,
fs.constants.W_OK
, and fs.constants.X_OK
(e.g.
fs.constants.W_OK | fs.constants.R_OK
). Check File access constants for
possible values of mode
.
If the accessibility check is successful, the promise is resolved with no
value. If any of the accessibility checks fail, the promise is rejected
with an <Error> object. The following example checks if the file
/etc/passwd
can be read and written by the current process.
import { access, constants } from 'node:fs/promises';
try {
await access('/etc/passwd', constants.R_OK | constants.W_OK);
console.log('can access');
} catch {
console.error('cannot access');
}
Using fsPromises.access()
to check for the accessibility of a file before
calling fsPromises.open()
is not recommended. Doing so introduces a race
condition, since other processes may change the file's state between the two
calls. Instead, user code should open/read/write the file directly and handle
the error raised if the file is not accessible.