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
🌎 The disappearance of the Sodder children in 1945 remains unsolved. Five siblings vanished after a house fire in Fayetteville, West Virginia. Investigators found no remains in the ash, and sightings were later reported but never verified. A billboard seeking answers stood along Route 16 for decades. ✨
#history⚡#disappearance⚡#mystery
👉subscribe Interesting Planet
🌎 In 2009, French aircraft Air France Flight 447 disappeared over the Atlantic during a flight from Rio de Janeiro to Paris. All 228 people on board died. The plane's wreckage was not found for nearly two years, when deep-sea searches located the main debris field at a depth of 3,900 meters. ✨
#aviation⚡#disappearance⚡#ocean
👉subscribe Interesting Planet
👉more Channels
🌎 In 1815, the British brig HMS Rosalie was found abandoned and drifting near the Bahamas. The ship’s sails were set, and cargo untouched, but not a single crew member was found onboard. Official records note that the ship’s logbook and personal belongings were still present when discovered. ✨
#disappearance⚡#maritime⚡#mystery
👉subscribe Interesting Planet
🌎 In 1973, Australian pilot Frederick Valentich disappeared while flying a Cessna 182L over Bass Strait. During radio contact, he reported a strange, unidentified craft circling his plane before transmission was lost. Despite a large search, neither Valentich nor his aircraft were ever found. ✨
#disappearance⚡#aviation⚡#australia
👉subscribe Interesting Planet
👉more Channels
🌎 In 1872, the Mary Celeste was found adrift in the Atlantic Ocean—its crew vanished without a trace, leaving food, cargo, and the ship untouched. This unsolved maritime mystery has puzzled historians ever since. ✨
#disappearance⚡#ship⚡#mystery
👉subscribe Interesting Planet
🌎 In 1925, British explorer Percy Fawcett vanished in Brazil's Amazon rainforest while searching for the lost city of "Z." Fawcett, his son, and a companion were last seen near the Upper Xingu River. Despite dozens of rescue missions over decades, no confirmed trace of the expedition was ever found. ✨
#amazon⚡#disappearance⚡#exploration
👉subscribe Interesting Planet
👉more Channels