[sluongng]

Why not https://man7.org/linux/man-pages/man2/flock.2.html?

[yjftsjthsd-h]

Nit: Probably https://man7.org/linux/man-pages/man1/flock.1.html (shell command, not the underlying libc function)

[anitil]

This was my first thought and I suppose flock(1) could be used to recreate a lot of this. But it does come with some other quality-of-life improvements like being able to list all currently-used locks, having a lock holdable by N processes etc.

[Zacru]

Because that's a syscall ;) https://man7.org/linux/man-pages/man1/flock.1.html is the command line manual.

I would say one good reason is that

  waitlock myapp &
  JOB_PID=$!
  # ... do exclusive work ...
  kill $JOB_PID

is a lot easier to use and remember than

  (; flock -n 9 || exit 1; # ... commands executed under lock ...; ) 9>/var/lock/mylockfile

[yjftsjthsd-h]

Why

  (; flock -n 9

and not

  ( flock -n 9

?

[apopapo]

It's a "for" loop.

[marklgr]

Could you elaborate?

[apopapo]

A for loop in a shell script may sometimes look like this:

`for ((i = 0 ; i < max ; i++ )); do echo "$i"; done`

Here this is essentially a "while" loop, meaning it will keep executing the commands as long as we don't reach `exit 1`.

(; flock -n 9 || exit 1; # ... commands executed under lock ...; )

[yjftsjthsd-h]

It doesn't seem to work?

  [~] 0 $ ( flock -n 9 || exit 1; echo in loop ; sleep 3 ; echo done working ; ) 9>~/tmp/mylock
  in loop
  done working
  [~] 0 $ (; flock -n 9 || exit 1; echo in loop ; sleep 3 ; echo done working ; ) 9>~/tmp/mylock
  -bash: syntax error near unexpected token `;'
  [~] 2 $

(This is bash)

[permalac]

Flock can be used in a single line for example for cronjobs.

Flock -s file && script.

Pretty simple. (I forgot the argument, I think is -s..

[bigattichouse]

just pushed a change so now it's:

waitlock myapp & #... do stuff waitlock --done myapp

[ethan_smith]

flock is indeed built-in: `flock -xn /tmp/mylock.lock -c "echo running locked command"` does mutex locking in bash. Your tool might offer better ergonomics or features beyond flock's capabilities?