Les Mikesell wrote:
Robert Nichols wrote:
These shouldn't make any difference. The limit is on the size of the
expanded shell command line.
Really?
$ M=0; N=0; for W in `find /usr -xdev 2>/dev/null`; do M=$(($M+1));
N=$(($N+${#W}+1)); done; echo $M $N
156304 7677373
vs.
$ /bin/echo `find /usr -xdev 2>/dev/null`
bash: /bin/echo: Argument list too long
For the first case, the shell never tries to pass the list as command
arguments.
It builds the list internally, limited only by memory size, and
processes the
words one by one.
Is that peculiar to bash? I thought the `command` construct was
expanded by shells into the command line before being evaluated.
I can't answer for how any particular shell allocates its internal memory,
but yes, the shell does read the entire output from `command` before
evaluating it. If this data is simply being used internally it never
gets passed to the kernel as an argument to exec() and thus can never
result in errno==E2BIG (7, "Argument list too long").
--
Bob Nichols "NOSPAM" is really part of my email address.
Do NOT delete it.
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