UNIX for Dummies Questions & Answers

what is the maximum number ls can list down

I've seen it stopping at 30000 files, you should try listing them at smaller chunks with find & xargs

ls -f
should be able to handle any size of directory. The other forms of ls try to read the entire directory into virtual memory for sorting and can bump into the max size for a data segment.

Wildcard arguments to a command may be expanded by the shell before the command executes - this is globbing.

If this happens, like ls * instead of ls, then the problem is the max size of arguments in bytes to an exec - something listed as ARG_MAX in limits.h. Note: _POSIX_ARG_MAX (4096) is what POSIX says to use, not what your system implmentation supports. ARG_MAX is usually way larger then 4096. And is the one that counts.

You could easily bump into ARG_MAX problems with a huge directory with longer filenames, as well.

how to ensure ls didn't break in the middle due to max number limits in my script

i am not sure whether ls -f will help in this

One way:
Try creating a simple ls in C or perl or python, using opendir(), readdir().

Did just plain ls -f with<no wildcards> break?

It should be okay unless something else has a problem - like the filesystem. filesystems have limits to the number of files they can support. Or they can become corrupted. You can look in /etc/fstab to see what filesystem supports the directory you are looking at.

Waht kinds of errors are you seeing now?

Nitpicking a bit for the records:

If the run time limit can be modified, ARG_MAX from the headers won't reflect it.
But "getconf ARG_MAX" (using the libc call "sysconf") usually is correct.

However, on systems without fixed limit (e.g. Linux-2.6.23 ff., or Hurd), even getconf might report some obsolete historic default value (and it does so on Linux).
Possible reasons might be: either trying not to confuse autoconf scripts and alike, or the libc just couldn't catch up yet.