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Re: extension of file-test primitives?

From: dethrophes
Subject: Re: extension of file-test primitives?
Date: Wed, 23 Aug 2017 16:49:34 +0200
User-agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0

Well technically I don't *have* to accept the performance penalty.

As I can just use the posix comform syntax, which is quicker.

And just becasue I was curious as to how much quicker it is. Now admittedly it's not the biggest difference in perf, but I don't see any real point in using a slower one.

        test -f "${1:?Missing Test File}" -a -x "${1}"

        test -f "${1:?Missing Test File}" && test -x "${1}"

        local cnt=${1:?Missing repeat count}
        local test_func=${2:?Missing Test Function}
        local test_file=${3:?Missing Test File}

        echo "${test_func}" "${test_file}"
        while [ $(((cnt -= 1 ) )) != 0 ]; do
      "${test_func}" "${test_file}"
    : ${TMPDIR:=/tmp}
        touch "${TMPDIR}/file"
        touch "${TMPDIR}/exec_file"
        chmod a+x "${TMPDIR}/exec_file"
        time test_case 10000 test_file_1 "${TMPDIR}/file"
        time test_case 10000 test_file_2 "${TMPDIR}/file"
        time test_case 10000 test_file_1 "${TMPDIR}/exec_file"
        time test_case 10000 test_file_2 "${TMPDIR}/exec_file"

~/ks_qnx/test_bash.sh setup_test
test_file_1 /tmp/file

real    0m0.132s
user    0m0.128s
sys     0m0.004s
test_file_2 /tmp/file

real    0m0.148s
user    0m0.116s
sys     0m0.028s
test_file_1 /tmp/exec_file

real    0m0.138s
user    0m0.128s
sys     0m0.008s
test_file_2 /tmp/exec_file

real    0m0.153s
user    0m0.128s
sys     0m0.024s

Am 23.08.2017 um 16:27 schrieb Chet Ramey:
On 8/23/17 10:24 AM, Dethrophes wrote:

Which I always understood as the correct way of doing this in the
first place...

It's not as good as multiple test commands: test -f file && test -x
There's no ambiguity and you get short-circuiting.
Only if you are using the test built-in, otherwise the latter means 2 
spawns/forks however the shell in question calls the test exec.
Since bash has a test builtin, this isn't exactly on point. But you have
to accept this kind of micro-inefficiency with a shell that sacrifices
speed for size.

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