Shell Programming and Scripting

And do you get an error message when you do:

Code:

for i in *; do : ; done

@Scruti
You got me : the "for" loop runs fine .

Ok i got it : this is a limitation of the ls command (not the shell expansion)
correct ?

ls command should be coded to be able to handle huge number of argument. But I suppose it is choice of design, for performance reason.
Do you have any clue ?

Code:

$ print *
bash: print: command not found
$ sh print *
bash: /usr/bin/sh: Arg list too long
$

It is a limitation for external commands:
POSIX: limits.h

So the number of arguments that external commands can handle is limited by ARG_MAX. This is not the case for shell builtins.

It's an operating system limitation. They can't. Ergo, you should program in ways that don't cram potentially unlimited numbers of arguments into a commandline. In some shells, you can get away with cramming billions of arguments into a builtin (and ONLY a builtin), but you really can't depend on that.

Bad:cat * > output
Good:ls | xargs cat > output xargs understands maximum arguments and can split them intelligently across several cat calls.

The same goes for things like for LINE in `cat foo` ; do ... ; done when foo exceeds 4K in size you may discover the maximum size of a shell variable on your system. Instead: while read LINE ; do ... ; done < foo

Essentially the idea's the same in all cases: Never force the shell to hold an entire anything in memory. (That actually applies to most programming languages, but shell makes it deceivingly easy to do so...) You'll hit walls at inconvenient times and it's never efficient. Process in bits.