Employing the mechanism from the answer at https://unix.stackexchange.com/a/274499/5132 in the Z shell:
(
flock -x 200
echo "test";
) 200>mylockfile2
returns
zsh: parse error near `200'
While in bash it works correctly. What may be the issue here?
Bash is the only shell that allows the user to open a fd higher than 9 directly using the normal redirection syntax. so in other shells the command is equivalent to (...) 200 1>mylockfile2, which is a syntax error. posix only mandates supporting 0-9. If you really want to ensure the fd used with the lock isn't already in use, you can use syntax specifically designed to open the next available fd.
(foo "$lockfd";...) {lockfd}>file
foo or lockfd refer to? Is lockfd a special variable?
{lockfd}
yash also supports 200> file. rc, es, akanga as well with the >[200] file syntax.
zsh is not bash despite some efforts between the two camps of peeking over the fence and stealing ideas from one another. Also, flock appears to come from util-linux so portability may be limited. A ZSH solution might instead use the zsystem module; this module provides a flock command:
#!/usr/bin/env zsh
zmodload zsh/system
(
local lockvar
touch lockfile
zsystem flock -f lockvar lockfile
print >&2 got lock
sleep 10
zsystem flock -u $lockvar
print >&2 end lock
)
