А знаете ли вы, что в Bash есть особая переменная "$_" ? Из описания можно узнать, что в переменную "$_" помещается последний аргумент последней команды.
Что-то знакомое? Конечно, в Python есть примерно тоже самое.
Мы знаем, что дата первого релиза Bash (8 июня 1989) несколько раньше чем первый релиз Python (20 февраля 1991). Если учесть, что по задумке автора Python это агрегация самых успешных практик отовсюду, можно ли сказать что именно эта фишка к нему пришла из Bash? Ни подтверждения ни опровержения я пока не нашел.
Давайте просто считать это совпадением 😉
А как это может быть полезно в Bash?
Приведу простой пример, который оценят те, кто часто работает в терминале.
Допустим, нам надо создать директорию и зайти в неё. Что обычно делаем?
:~$ mkdir foldername
:~$ cd foldername
:~/foldername$
Как это сделать в одну команду?
:~$ mkdir foldername && cd foldername
:~/foldername$
Уже лучше, но хочется короче, без повторов. Вот тут и пригодится наша переменная. Напомню, что в неё сохраняется последний аргумент предыдущей команды.
:~$ mkdir foldername && cd $_
:~/foldername$
_________________
PS.
Символы "&&"" разделяют команды и означают, что требуется выполнить вторую команду только если первая завершилась успешно.
#linux#tricks
So our son got a telescope for his birthday. But as he is way too young to use it, guess who can now take a (not perfect) look at the old gods.
Above you see an image of the moon shot with a mobile cam through the lens. I know, poor quality. But I will improve.
If you live in Central Europe and have clear skies, look south now and watch Jupiter and Saturn following the Moon.
Jupiter is a bright object some degrees to the east from the Moon, while Saturn follows Jupiter as a tiny speck in the sky.
#astronomy
@EuropeanTribalism
On comets
This is an image of the comet C/2006 P1, commonly known as McNaught.
Scientists observed its tail modifying attributes of the solar wind, which is impossible by the standard model, which claims that comets are 'dirty snowballs'.
In reality, comets are charged rocks which spend most of their time in the outer regions of the solar system, where they accumulate a negative charge until they start their journey into the center of the solar system.
Their tails are visible electric discharge phenomena.
To recognize the electrical nature of comets, means recognizing the electrical nature of the universe and is key in understanding spirituality.
#astronomy#comets
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🌍 Earth travels around the Sun at about 107,000 kilometers per hour, yet we don’t feel it thanks to the planet’s steady movement and protective atmosphere. ✨
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🌎 A star called KIC 8462852, also known as Tabby's Star, has shown highly unusual, unpredictable dips in brightness. Unlike typical stars, its brightness sometimes drops by up to 22%. Astronomers have ruled out planets and suspect dust clouds or fragments from a disintegrating comet might be causing the effect. ✨
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🌎 Astronomers have detected rapid radio bursts—millisecond-long signals from distant space. These intense pulses hint at extreme events, like collapsing stars or magnetars, yet their exact origin remains one of space’s most intriguing mysteries. ✨
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🌎 Space isn’t silent—astronomers have recorded eerie “whistles” and “choruses” from planets like Jupiter. These radio waves, caused by charged particles moving through magnetic fields, are transformed into sound waves we can hear when played back on Earth. The haunting tunes of space reveal hidden cosmic activity all around us. ✨
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🌎 Saturn is famous for its bright rings, but these rings are mostly made of tiny bits of ice and rock, ranging from dust-sized grains to pieces several meters across. Scientists estimate the rings are relatively young—no more than 400 million years old. ✨
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🌎 Some planets in our Solar System have extreme day lengths. Venus rotates so slowly that a single day there lasts 243 Earth days, making its day longer than its year. Mercury also has unusual days—one day-night cycle equals 176 Earth days. ✨
#planets⚡#astronomy⚡#space
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