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
🌍 Some earthquake "swarms" can hit the same spot repeatedly over weeks or months, releasing energy in small bursts instead of one big quake—often in volcanic or tectonic hot zones. ✨
#earthquakes⚡#tectonics⚡#geology⚡#geography⚡#nature⚡#earth
👉subscribe Amazing Geography
👉more Channels
🌍 The planet’s largest earthquake ever measured—a magnitude 9.5—struck Chile in 1960. This event released so much energy it caused land to drop by up to two meters along the coast. ✨
#tectonics⚡#earthquakes⚡#geology⚡#geography⚡#nature⚡#earth
👉subscribe Amazing Geography
👉more Channels
🌍 One of the fastest-moving tectonic faults is in Turkey, with plates shifting up to 23 millimeters per year. This constant motion makes the region prone to frequent, sometimes devastating earthquakes. ✨
#tectonics⚡#earthquakes⚡#geology⚡#geography⚡#nature⚡#earth
👉subscribe Amazing Geography
👉more Channels
🌍 Some tectonic plate boundaries move so slowly they create “silent earthquakes”—huge shifts that happen over days or weeks, releasing energy without sudden shaking. ✨
#tectonics⚡#earthquakes⚡#geology⚡#geography⚡#nature⚡#earth
👉subscribe Amazing Geography
👉more Channels
🌍 Some large earthquakes can trigger aftershocks that last for months or even years. These smaller quakes are part of the Earth’s ongoing adjustment after a major tectonic shift. ✨
#tectonics⚡#earthquakes⚡#geology⚡#geography⚡#nature⚡#earth
👉subscribe Amazing Geography🌍
🌍 The strongest earthquakes ever recorded can move entire cities by several meters in seconds. In 2011, Japan’s coastline shifted east by up to 5 meters due to a massive plate boundary quake. ✨
#earthquakes⚡#tectonics⚡#geology⚡#geography⚡#nature⚡#earth
👉subscribe Amazing Geography🌍
🌍 The San Andreas Fault in California allows two massive tectonic plates to slip past each other. This boundary creeps a few centimeters each year but can unleash powerful earthquakes in sudden jolts. ✨
#tectonics⚡#earthquakes⚡#geology⚡#geography⚡#nature⚡#earth
👉subscribe Amazing Geography🌍
🌍 The ring-shaped chain of volcanoes called the "Ring of Fire" circles the Pacific Ocean, hosting about 75% of all active volcanoes on Earth and causing frequent earthquakes and eruptions. ✨
#volcanoes⚡#mountains⚡#tectonics⚡#geography⚡#nature⚡#earth
👉subscribe Amazing Geography
👉more Channels
🌍 The Atlantic Ocean is growing wider each year as the Americas slowly drift apart from Europe and Africa, adding about 2.5 centimeters annually—roughly the speed fingernails grow. ✨
#continents⚡#oceans⚡#tectonics⚡#geography⚡#nature⚡#earth
👉subscribe Amazing Geography
👉more Channels
🌍 The Eurasian and North American continents are moving apart by about 2.5 centimeters every year along the Mid-Atlantic Ridge, slowly widening the Atlantic Ocean over millions of years. ✨
#continents⚡#oceans⚡#tectonics⚡#geography⚡#nature⚡#earth
👉subscribe Amazing Geography
👉more Channels
🌍 The lithosphere’s tectonic plates move slowly, but sometimes collide to form tall mountain ranges like the Himalayas, linking Earth's rocky shell to the atmosphere and biosphere. ✨
#lithosphere⚡#tectonics⚡#mountains⚡#geography⚡#nature⚡#earth
👉subscribe Amazing Geography🌍
🌍 The Himalayas are rising by about 5 millimeters each year as the Indian and Eurasian plates continue to collide. This ongoing uplift makes these mountains among the youngest and fastest-growing on Earth. ✨
#mountains⚡#Himalayas⚡#tectonics⚡#geography⚡#nature⚡#earth
👉subscribe Amazing Geography🌍