fs.writeFileSync doesn't change the mode of existing file.

[gemwuu]

Version

16.4.0

Platform

macOS

Subsystem

Big Sur(11.2.3)

What steps will reproduce the bug?

echo "echo 11" > a && ls -l a && ./a
node -e "fs.writeFileSync('./a', 'echo 1111', {mode: 0o755})" && ls -l a && ./a

-rw-r--r--  1 test  staff  8 Aug 24 19:04 a
a.sh: line 1: ./a: Permission denied
-rw-r--r--  1 test  staff  9 Aug 24 19:04 a
a.sh: line 2: ./a: Permission denied

How often does it reproduce? Is there a required condition?

no condition

What is the expected behavior?

should print 1111.

What do you see instead?

a.sh: line 2: ./a: Permission denied

Additional information

No response

[rayw000]

Same issues happen on fs.appendFile and fs.appendFileSync.

Let me handle this.

[targos]

I'm not sure what the behavior is supposed to be but it doesn't seem like a bug. The mode is probably only used when a new file is created.
@nodejs/fs

[rayw000]

I'm not sure what the behavior is supposed to be but it doesn't seem like a bug. The mode is probably only used when a new file is created.
@nodejs/fs

Or, should we describe this in the document? Currently none of these functions say they will ignore mode option if the file exists. This may be surprising.

[gemwuu]

I'm not sure what the behavior is supposed to be but it doesn't seem like a bug. The mode is probably only used when a new file is created.
@nodejs/fs

Yes, When I looked into the source code L2153, writeFileSync call openSync firstly，which has explained in the doc, it shall make the POSIX syscall open.