Following ARG_MAX, maximum length of arguments for a new process it seems like ARG_MAX
is wrongly (or at least ambiguously) defined on my Mac Mini 3,1 running Ubuntu 12.04:
$ getconf ARG_MAX # arguments
2097152
$ locate limits.h | xargs grep -ho 'ARG_MAX[ \t]\+[0-9]\+' | uniq | cut -d ' ' -f 8
131072
The actual limit seems to be somewhere between these:
$ cd "$(mktemp -d)"
$ touch $(seq 1 131072) && find . -mindepth 1 -printf x | wc -c && rm *
131072
$ touch $(seq 1 131073) && find . -mindepth 1 -printf x | wc -c && rm *
131073
$ touch $(seq 1 $(getconf ARG_MAX)) && find . -mindepth 1 -printf x | wc -c && rm *
bash: /usr/bin/touch: Argument list too long
I did a small search:
cd "$(mktemp -d)"
min=131072
max=2097152
while true
do
search=$((min + (max - min) / 2))
if touch $(seq 1 $search) 2>/dev/null
then
min=$search
else
max=$search
fi
[[ $((max - min)) -le 1 ]] && echo "ARG_MAX = $min" && break
done
Eventually this resulted in ARG_MAX = 314290
, which doesn't seem to have any relation to either of the ARG_MAX
values found before. Is this normal? Is there a simpler way to find the actual ARG_MAX
?
Did I misunderstand the definition of ARG_MAX? It seems it's actually the byte (or possibly character) length of the arguments with or without (?) the separating spaces. If it's really the byte length, are there also other restrictions?
Best Answer
Yes, it's the length in bytes, including the environment.
Very roughly:
linux sysconf
POSIX 2004 limits.h