Argument list too long

[Steven W. Orr]

On Wednesday, Aug 1st 2007 at 14:03 -0600, quoth Phil Meyer:

=>Ashley M. Kirchner wrote:
=>> 
=>>    Question: at what point would commands such as 'ls', 'cp' and others
=>> consider the argument list too long?  The reason I'm asking is because I'm
=>> getting random results here.  One time 'ls' would tell it the argument list
=>> is too long when the file count in the folder reached around 2,000 files.
=>> Another, like this morning, it let me go all the way to 2,600+ before
=>> complaining.  And just now it reached 1,900 files and already 'ls' is
=>> complaining.  That seems random to me.  Is there a set number that causes
=>> all of these commands to fail with 'Argument list too long' or what
=>> convoluted algorithm is used to figure it out?
=>> 
=>
=>It is based upon a max string length, not number of files.  That is the
=>purpose for the command xargs.
=>
=>Whenever you are likely to exceed the maximum command line, put xargs in the
=>middle, ie:
=>
=>$ find /usr/include -name \*.h -print | xargs grep SIGKILL
=>
=>Does that make sense?
=>
=>xargs knows what the max string length is for the system its on, and cuts the
=>command line into pieces accordingly and feeds it in pieces to the arguments
=>given.

Use xargs as described above. Learn it. Use it. Love it.

One more detail for the completely anal: The value of ARG_MAX in limits.h 
is the total bytecount of a commandline *minus* the size of your 
environment. i.e., ARG_MAX - $(wc -c $(env))

-- 
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steveo at syslang.net