reload_flag=""
if [[ -n "${DEBUG}" ]]; then
reload_flag="--reload"
fi
if [[ -n "${WORKER_COUNT}" ]]; then
workers=${WORKER_COUNT}
else
workers=2
fi
gunicorn --workers ${workers} \
--bind 0.0.0.0:8000 \
${reload_flag} main.wsgi
Писали такие конструкции чтобы проверить наличие флага и сформировать команду правильно?
На самом деле можно сделать тоже самое проще. Для этого используются операторы условной подстановки, доступные в оболочках семейства POSIX.
:- для установки значений по умолчанию
${WORKER_COUNT:-2}
Если переменная не объявлена, то будет дефолтное значение 2.
:+ подставляет указанный текст, если переменная не пуста
${DEBUG:+--reload}
Если что-то есть в переменной то распечатается текст после символа +, в противном случае - ничего. Удобно для опциональных флагов, как в нашем примере.
Итого наш скрипт может выглядеть так:
gunicorn --workers ${WORKER_COUNT:-2} \
--bind 0.0.0.0:8000 \
${DEBUG:+--reload} main.wsgi
Есть еще два оператора.
:= не только подставить дефолтное значение, но и присвоить его переменной, если она пуста
# никаких переменных еще нет
VAL1=${VAL2:=hello}
# теперь доступны обе
echo $VAL1 $VAL2
# hello hello
:? остановить выполнение с ошибкой, если переменной нет.
echo ${MISS:?is required}
bash: MISS: is required
Код выхода будет 1.
#tricks#linux
🌎 Multiple theories in modern physics suggest parallel worlds or dimensions could exist, but no direct experimental evidence has ever been found. String theory predicts extra spatial dimensions, and some cosmological models propose the idea of a "multiverse," where many universes exist with different physical laws. As of 2024, all searches for measurable proof—such as deviations in gravity or missing energy—have reported no confirmed signs of parallel worlds. ✨
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🌎 In physics, the concept of a "multiverse" proposes that our universe could be just one of many coexisting universes, each with different physical laws. This idea arises in cosmic inflation theory, where rapid early expansion could have created countless separate "bubble universes." The multiverse hypothesis is explored by leading scientists but remains unproven, and no direct evidence has yet been observed. ✨
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🌎 The "string theory landscape" in physics proposes that more than 10^500 possible universes, each with different physical laws, could exist within higher-dimensional space. This idea stems from mathematical solutions to string theory equations, where our universe is just one possibility in a vast "multiverse" of parallel worlds. ✨
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🌎 Scientists exploring the mysteries of parallel worlds suggest that, according to quantum mechanics, alternate dimensions could exist alongside our own—each with its unique version of reality. Though unproven, this idea helps explain puzzling phenomena in physics and inspires everything from science fiction to cutting-edge research about the nature of our universe. ✨
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🌎 The "brane multiverse" is a scientific idea suggesting our universe might be a three-dimensional "brane" floating in higher-dimensional space. Some versions of string theory propose multiple branes could exist close together, and rare collisions might even trigger new big bangs. The concept arises from efforts to unify gravity with quantum physics. ✨
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🌎 Quantum physics allows for the concept of “superposition,” where particles exist in multiple states at once. This principle forms the basis for theories suggesting that parallel worlds or dimensions might exist alongside our own. The famous “double-slit experiment” demonstrates superposition, as particles act as if they travel through two paths simultaneously. ✨
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🌎 The concept of parallel worlds is grounded in the "many-worlds interpretation" of quantum mechanics, proposed by physicist Hugh Everett in 1957. It suggests every quantum event may split reality into new branches, creating countless coexisting universes. Unlike science fiction, this idea remains unproven and is debated among physicists, but it offers possible explanations for phenomena like quantum superposition. ✨
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