entr on big sur is not in sync

[varvello]

Hi guys,
It seems to me that entr is monitoring files one step behind.
I.e. the script: ls | entr -p echo /_ is always printing the previous file I've changed. It only syncs if I press the spacebar. The p flag isn't really necessary.

Am I doing something wrong?

[eradman]

@varvello, thanks for reporting this: on Big Sur events are reported in a strange way. For the following test I set export EV_TRACE=1 and then appended some test to three different files

$ echo xyz >> c
$ echo xyz >> b
$ echo xyz >> a

OpenBSD

$ ls a b c | entr echo /_
open_max: 16384
/tmp/a
0/1: fflags: 0x6 r 100644 c
/tmp/c
0/1: fflags: 0x6 r 100644 b
/tmp/b
0/1: fflags: 0x6 r 100644 a
/tmp/a

MacOS

$ ls a b c | entr echo /_
open_max: 256
/Users/eradman/tmp/a
0/1: fflags: 0x2 r 100644 c
/Users/eradman/tmp/c
0/1: fflags: 0x8 r 100644 c
0/1: fflags: 0x2 r 100644 b
/Users/eradman/tmp/c
0/1: fflags: 0x8 r 100644 b
0/1: fflags: 0x2 r 100644 a
/Users/eradman/tmp/b
0/1: fflags: 0x8 r 100644 a

I'll investigate this further

[eradman]

Here is a different view of the events using the diagnostic utility kqueue-touch

$ echo xyz >> test-file

OpenBSD

event 1/1: flags: 0x21 fflags: 0x6

MacOS

$ ./kqueue-touch
event 1/1: flags: 0x21 fflags: 0x8
event 1/1: flags: 0x21 fflags: 0x4
event 1/1: flags: 0x21 fflags: 0x2
event 1/1: flags: 0x21 fflags: 0x8

That last event is coming in about a second later! This is wrong, and certainly new behavior for any OS. For reference:

/*
 * data/hint flags for EVFILT_VNODE, shared with userspace
 */
#define NOTE_DELETE     0x0001                  /* vnode was removed */
#define NOTE_WRITE      0x0002                  /* data contents changed */
#define NOTE_EXTEND     0x0004                  /* size increased */
#define NOTE_ATTRIB     0x0008                  /* attributes changed */
#define NOTE_LINK       0x0010                  /* link count changed */
#define NOTE_RENAME     0x0020                  /* vnode was renamed */
#define NOTE_REVOKE     0x0040                  /* vnode access was revoked */
#define NOTE_TRUNCATE   0x0080                  /* vnode was truncated */

[eradman]

@varvello I pushed a fix for this in commit fba2e90. Prior this this entr assumed that events would never be queued by the operating system and delivered later, which seems to be what Big Sur is doing.

[varvello]

Thanks @eradman the fix fba2e90 is working

[eradman]

Super!