Date: Mon, 01 Mar 1999 05:58:43 +1000 From: Greg Black <gjb@comkey.com.au> To: cjclark@home.com Cc: sogon@psytrance.com, freebsd-questions@FreeBSD.ORG Subject: Re: problem with cat command Message-ID: <19990228195843.12217.qmail@alpha.comkey.com.au> In-Reply-To: <199902281851.NAA13328@cc942873-a.ewndsr1.nj.home.com> of Sun, 28 Feb 1999 13:51:58 EST References: <199902281851.NAA13328@cc942873-a.ewndsr1.nj.home.com>
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> > does anyone know what the limit of args to the cat command is,
>
> The command itself appears to have no limit (from a quick peak at
> '/usr/src/bin/cat/cat.c'). The limit you'll probably hit is the number
> of arguments the shell is willing to take.
The critical limit is determined by the kernel. Read the man
pages for sysctl(3) and execve(2) for details. On my system,
I get:
$ sysctl kern.argmax
kern.argmax: 65536
You cannot change this value on a running system.
> > basically what i want to do is cat 15000 files into another file how would i
> > do this
>
> Break it up into chunks. How to do this depends on your shell of
> choice and the way the files are named.
This problem is easily solved by the standard utility xargs(1).
If the original command line was
cat * > newfile
then replace it with
ls | xargs cat >> newfile
Note that you can't specify all the files to xargs in the same
way that already failed when you tried to invoke cat, for the
same reasons. You have to get a program to generate the names
as output and then feed that to xargs. Another program to do
this if ls(1) doesn't work for you is find(1). For instance,
say you had 50,000 files in some tree and you wanted all the
ones with an 'e' in their names to be removed, you could do
find . -type f -name '*e*' | xargs rm
--
Greg Black <gjb@acm.org>
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