While trying to save `pstree -ap` output to a file and I'm getting a really strange error:

$ pstree -ap > pstree.txt
File size limit exceeded

Of course, I don't have any filesize limit on this system:

$ ulimit -f
unlimited

It turns out that pstree itself sets the filesize limit -- probably in some kind of a sandboxing effort:

$ strace -e /limit pstree -ap > /dev/null
prlimit64(0, RLIMIT_NPROC, {rlim_cur=0, rlim_max=0}, NULL) = 0
prlimit64(0, RLIMIT_FSIZE, {rlim_cur=0, rlim_max=0}, NULL) = 0
prlimit64(0, RLIMIT_NOFILE, {rlim_cur=0, rlim_max=0}, NULL) = 0
+++ exited with 0 +++

So, obvious workaround like intermediate `cat` works:

$ pstree -ap | cat > pstree.txt
$ echo $?
0
$ wc pstree.txt
  578  2120 22017 pstree.txt

But, well, such limitation on where output can go definitely looks like a bug to me.